The Fiero was available with air conditioning all model years, 1984 through 1988. During that time, there were three compressors used: DA6, HR6, and V5. The DA6 compressor was used on 84 and 85 four cylinder cars, and 85-87 V6 cars, until some time in the 1987 model year, when GM changed over to the HR6 compressor, an improved version of the DA6, which was used on late 1987 V6 cars and 88 V6 cars. The following applies only to the DA6 and HR6 compressors, NOT the V5.
Being externally nearly identical, both the DA6 and HR6 compressors function the same way, and are interchangeable. However, the more reliable HR6 is recommended any time repair or replacement is needed. The HR6 is also rated for use with R-134A refrigerant when doing a retrofit.
Both compressors use two switches mounted in the back as safety devices: the low pressure cut-off switch, and the high-pressure cut-off switch. These switches are interchangeable between compressors.
Switch Functions
The low pressure cut-off switch is normally open. This can be tested by using a multimeter set to continuity mode. There should be no continuity between the large round metal body, and the contact on top of the switch. When pressures inside the compressor reach a certain point, the switch will close, and turn on the radiator fan. This is designed to increase airflow over the condenser, and lower the system pressure. The switch closes at approximately 280 psi.
The high-pressure cut-off switch is normally closed. This can be tested by using a multimeter set to continuity mode. There should be continuity between the large round metal body, and the contact on top of the switch. When pressures inside the compressor reach a certain point, the switch will open, turning off the compressor, disengaging the compressor clutch plate. The switch opens at approximately 425 psi, and closes at approximately 200 psi.
New VS Old Style Switches
For whatever reason, the old style switches are no longer available. They have been replaced by switches that use new connectors, and are no longer grounded through the compressor body. When changing the old switches out for the new style, one side of the new connectors needs to be grounded, and the other side connected to the original wiring. The new connectors may be purchased with or without the new style switches.
The two types of switches used originally in the Fiero were the red pin switch, and the white 'mushroom' switch. The red switch is the high pressure cut-off switch, and the white switch is the low pressure cut-off switch. The easiest way to remember this is the white switch controls the radiator fan, uses the same type of connector as the radiator cooling fan switch.
Both switches have been replaced by the following:
Santech part # MT0671 Santech part # MT0678
Both of the above include the switch, connector, o-ring, and C-clip, for ease of installation.
MT0671, replaces the low pressure (white mushroom) switch. It is normally open, and closes at 283 psi, and reopens at 210 psi. It is colored purple.
MT0678, replaces the high pressure (red pin) cut-off switch. It is normally closed, and opens at 430 psi, and closes again at 200 psi. It is colored blue.
Both switches include HNBR o-rings, typically green, that are both R-12 and R-134A compatible.
Replacement of the switches is the same as the originals: Remove the snap rings using snap ring pliers, and pull the switch straight up and out. Remove the old o-ring. Coat new o-ring in compressor oil, and place into groove in compressor. Push new switch into the compressor, and replace the snap ring.
Good info worth a positive. : However all HR 6 compressors do not have a high pressure switch. The 4.9L version comes to mind. For these applications a switch on an external switch port can be used.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
When I replace my fan switch on the compressor recently the replaced switch needed a new connector. The new connector, as listed above, comes with two wires as opposed to a single wire on the stock connector. The instructions with the new connector stated to connect one wire to the existing switch wire and the other wire to a ground. When the connector was wired according to the directions I was unable to turn off the radiator cooling fan wether the A/C was running, or not. The fan would also run any time the ignition switch was in ACC. with a cold cooling system. After a search here I found a posting that said to only connect one of the new connector wires to the existing wire and "do not" connect the other wire to the ground. Well, I disconnected the ground and the radiator fan operated as it was suppose to and all is good.
Great writeup RWDPLZ!!!
[This message has been edited by Kevin87FieroGT (edited 07-21-2011).]
2 terminal, high pressure cut-off switch from Factory Air / 4 Seasons, PART NUMBER: 35974 ($27.00) 2 terminal low pressure / condenser fan switch from Factory Air / 4 Seasons, PART NUMBER: 35969, ($29.79)
( Note that the color of the switch may be different from various manufacturers)
You might have to tinker around with connecting or disconnecting the ground wires, as I also had the problem of the constant running fan until I disconnected the low pressure switch ground wire. All works as it should since then and my A/C is still blowing COLD this summer.
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[This message has been edited by randye (edited 07-21-2011).]
Bump. This question is directed to RWDPLZ and RANDYE. I have an 88 GT that had for lack of a better term an "explosion" from the engine area last fall. A hazy mushroom cloud effect, it was something to see! The compressor was making a bit of noise for several weeks prior to that. I inspected the hoses and they seem fine between the firewall and compressor fitting. The compressor has some seepage around the front clutch area, so I assume the compressor exploded or that one of these switches blew out of the plug.
**If I buy a reman Four Seasons compressor, do they come with these switches installed or do I need to buy these separately? If they are not part of the package, how do you wire them in to the factory setup?
Bump. This question is directed to RWDPLZ and RANDYE. I have an 88 GT that had for lack of a better term an "explosion" from the engine area last fall. A hazy mushroom cloud effect, it was something to see! The compressor was making a bit of noise for several weeks prior to that. I inspected the hoses and they seem fine between the firewall and compressor fitting. The compressor has some seepage around the front clutch area, so I assume the compressor exploded or that one of these switches blew out of the plug.
**If I buy a reman Four Seasons compressor, do they come with these switches installed or do I need to buy these separately? If they are not part of the package, how do you wire them in to the factory setup?
The switches are NOT included with the Four Seasons Remanufactured compressor. You will need to buy the switches AND the new mating plugs for them.
To wire them into the OEM harness is fairly simple. You will just cut the original single switch wires on the car, (do one at a time so that you dont confuse the high pressure cutoff switch with the fan switch), and simply splice in one of the two wires from the new switch plug. The 2nd wire from each of the new plugs is a ground wire and you should run each of these wires to a good ground on the chassis or engine block.
NOTE: It doesnt matter which of the 2 wires you choose to splice into the harness or run to ground. Both switches simply complete or interrupt a circuit to ground. The reason for the 2 wires on the new switch connectors is that the old single wire switches grounded through the body of the A/C compressor and the new switches do not. Therefore the separate ground wire is required. ------------------
[This message has been edited by randye (edited 01-21-2013).]
The seepage around the front clutch area is probably the front seal gone bad. They can be replaced, but you need about $100 in special tools and the $20 part, better off buying a new compressor without any issues. If the switch blew out of the plug, the leak would be back where the switch was.
funny, I installed a new comp in my 85 five years ago WITH NO SWITCHES, and it blows ice cold.( I Live in FLA.) I believe that the 1 pressure switch at the drier up front will shut it down if it runs out of freon. So aren't those switches at the compressor "Redundant" ? "Good Post Info"
Technically it will work with no switches in a DA6 or HR6 system, BUT the switches are safety devices. The fan switch one is redundant, but the high pressure cut-off switch is definitely a good idea to have.
funny, I installed a new comp in my 85 five years ago WITH NO SWITCHES, and it blows ice cold.( I Live in FLA.) I believe that the 1 pressure switch at the drier up front will shut it down if it runs out of freon. So aren't those switches at the compressor "Redundant" ? "Good Post Info"
From what I know of the 87-88 model years, (your 85 might be different), the switch up front at the receiver / dryer is a pressure CYCLING switch. It turns the compressor on and off to maintain a selected system operating pressure. That switch is adjustable, (such as when we set it for using R12 or R134A in the system which operate at different optimal pressures) The radiator fan is also turned ON by the HVAC control head inside the dash when "A/C" is selected.
The two switches on the DA6 and HR6 compressor are arguably "redundant" (non-adjustable) safety switches, but considering the repair expense to the system from a failure of either of the two aforementioned switches, I am happy to know they are there and working properly.
[This message has been edited by randye (edited 03-08-2013).]
Originally posted by randye: From what I know of the 87-88 model years, (your 85 might be different), the switch up front at the receiver / dryer is a pressure CYCLING switch. It turns the compressor on and off to maintain a selected system operating pressure. That switch is adjustable, (such as when we set it for using R12 or R134A in the system which operate at different optimal pressures) The radiator fan is also turned ON by the HVAC control head inside the dash when "A/C" is selected.
The two switches on the DA6 and HR6 compressor are arguably "redundant" (non-adjustable) safety switches, but considering the repair expense to the system from a failure of either of the two aforementioned switches, I am happy to know they are there and working properly.
The fan control switch on the compressor is not really redundant. In defog mode, the control head does NOT command cooling fan operation (try it and see), but it does turn on the A/C compressor. The fan control switch turns on the fan once pressure in the a/c system rises.
Without it, your dehumidify function for the defogger won't work as well.
Not sure which switch goes into the respective ports.
Either switch can be installed in either port. Both ports communicate with the compressor's high-pressure manifold. That said, the wiring harness may favor one switch placement over another.
Either switch can be installed in either port. Both ports communicate with the compressor's high-pressure manifold. That said, the wiring harness may favor one switch placement over another.
Wow, thank you Marvin. Of all the threads nobody mentioned this. I was stressing over looking at pics trying to figure out if there were stampings to explain which was LO or HI side.
Here is a link to Santech's illustrated catalog and application guide. Everything you needed to know and then some. Page 79 (81) has identification, switch pressure specs, alternate part numbers and more.
After a shop sent me the wrong switches twice, and then the wrong pigtails, I used this catalog to get exactly what I needed. Hope it helps some others.
I would say its mandatory to replace the two switches. My 88 4cyl went 263,000 miles on the orig AC then one day I heard a swish type sound and no AC. Upon autopsy the high side switch had broken and pressure got high enough to pop the safety valve. As seen above I was able to get 2 new switches of the right color and put them in w my new system.
From what I know of the 87-88 model years, (your 85 might be different), the switch up front at the receiver / dryer is a pressure CYCLING switch. It turns the compressor on and off to maintain a selected system operating pressure. That switch is adjustable, (such as when we set it for using R12 or R134A in the system which operate at different optimal pressures) The radiator fan is also turned ON by the HVAC control head inside the dash when "A/C" is selected.
The two switches on the DA6 and HR6 compressor are arguably "redundant" (non-adjustable) safety switches, but considering the repair expense to the system from a failure of either of the two aforementioned switches, I am happy to know they are there and working properly.
I know this is an old thread... but I've seen this a few times in the archive... how do you suppose your system is working properly when you disconnected the ground wire?
I would posit that your switch is NOT capable of functioning with the ground disconnected. The so-called "low pressure" switch is really called the "Coolant fan a/c pressure switch". And with the ground disconnected it's incapable of turning on the radiator fan. Is that needed? Maybe, maybe not, but disconnecting the ground doesn't sound like the right answer to me.
My research seemed to reveal that if your fan runs all the time you have the wrong switch.
[This message has been edited by jscott1 (edited 05-18-2014).]
I know this is an old thread... but I've seen this a few times in the archive... how do you suppose your system is working properly when you disconnected the ground wire?
I would posit that your switch is NOT capable of functioning with the ground disconnected. The so-called "low pressure" switch is really called the "Coolant fan a/c pressure switch". And with the ground disconnected it's incapable of turning on the radiator fan. Is that needed? Maybe, maybe not, but disconnecting the ground doesn't sound like the right answer to me.
My research seemed to reveal that if your fan runs all the time you have the wrong switch.
Its been a LONG time since I messed around with the AC on my Fiero, and to be fair I DO indeed recall some sort of issues regarding a ground wire connection and a constantly running radiator fan, but I assure you Ol' Buddy I worked all the bugs out.
Last I looked, everything was wired up all Kosher and proper.
I believe I even said:
quote
Originally posted by randye:
The switches are NOT included with the Four Seasons Remanufactured compressor. You will need to buy the switches AND the new mating plugs for them.
To wire them into the OEM harness is fairly simple. You will just cut the original single switch wires on the car, (do one at a time so that you dont confuse the high pressure cutoff switch with the fan switch), and simply splice in one of the two wires from the new switch plug. The 2nd wire from each of the new plugs is a ground wire and you should run each of these wires to a good ground on the chassis or engine block.
NOTE: It doesnt matter which of the 2 wires you choose to splice into the harness or run to ground. Both switches simply complete or interrupt a circuit to ground. The reason for the 2 wires on the new switch connectors is that the old single wire switches grounded through the body of the A/C compressor and the new switches do not. Therefore the separate ground wire is required.
The fan SHOULD be on constantly when the AC is selected, and the fan should cycle on and off normally with the fan control switch when the AC is off, (on the 2.8 or 3.4 swap), or thru the ECU... depending on your engine swap. ------------------
[This message has been edited by randye (edited 05-18-2014).]
funny, I installed a new comp in my 85 five years ago WITH NO SWITCHES, and it blows ice cold.( I Live in FLA.) I believe that the 1 pressure switch at the drier up front will shut it down if it runs out of freon. So aren't those switches at the compressor "Redundant" ? "Good Post Info"
Yes, they are redundant. The pressure cycling switch (on the receiver/dryer in the front compartment) controls the compressor clutch during normal operation.
However, if your pressure cycling switch fails or your fan fuse blows or a few other failures, you'll like having the safety switches in the compressor.
Bump because this is a good thread to keep out of the archives and also because I am experiencing an issue with these switches.
The problem is the plastic connector tab either broke off or the engine heat severely softens the connections on both my Fieros around the same time. This means the A/C shuts off in the middle of driving and I have to wait for the car to cool down before I can attempt to plug them back in.
Anyone else have the same problem? I have tried using zip ties to keep them tight but that only helps for so long.
Can I bypass at least the low pressure switch and rewire it directly? I cant remember which one would cause the fan to run constant even if the AC is off.
Bump. This question is directed to RWDPLZ and RANDYE. I have an 88 GT that had for lack of a better term an "explosion" from the engine area last fall. A hazy mushroom cloud effect, it was something to see! The compressor was making a bit of noise for several weeks prior to that. I inspected the hoses and they seem fine between the firewall and compressor fitting. The compressor has some seepage around the front clutch area, so I assume the compressor exploded or that one of these switches blew out of the plug.
**If I buy a reman Four Seasons compressor, do they come with these switches installed or do I need to buy these separately? If they are not part of the package, how do you wire them in to the factory setup?
Do not get a reman, spend a little extra and get a new one. The new ones have dowel pins to keep the case aligned and have 10cyls instead of 6. My first reman lasted less than 50 miles, the new one has been blowing cold for a year and draws less on the engine.
thanks but that's not what I was asking on this latest issue. Two years after the entire repair, the switches have weak clips holding the plug firmly in place. So I will be driving along and they just come unseated or slightly undone from the heat and the AC stops working. Very frustrating. I want to bypass one of the switches and fuse the wires together.
thanks but that's not what I was asking on this latest issue. Two years after the entire repair, the switches have weak clips holding the plug firmly in place. So I will be driving along and they just come unseated or slightly undone from the heat and the AC stops working. Very frustrating. I want to bypass one of the switches and fuse the wires together.
Try to put a very small dab of silicone or RTV sealant on one side of the switch on the outside of the plastic housing where it will NOT interfere with the metal to metal contact of the plug. Connect it back up and let it set for a few hours to cure. Make sure both surfaces, (switch and plug), are CLEAN and OIL FREE. Wipe off with alcohol before applying the sealant. It should only require a tiny spot, approx. the size of a #2 pencil eraser, or less to hold the plug in place and still be able to pull it off later if the need arises.
OH..and yes, *never* buy a *remanufactured A/C compressor like I did. I might last for YEARS and operate perfectly and still be going strong in Florida heat when you overhaul the A/C properly.
(I don't work for Four Seasons and I sure don't get anything from them for my comments. All I can say is that of the 4 different vehicles that I have properly installed their *remanufactured* products on, NOT ONE has failed for over 4 years of use in Florida summer heat.)
[This message has been edited by randye (edited 07-25-2015).]
You may have had good luck with remans, but if your replacing an HR6 compressor the new design eliminates the weak point in the originals. It's worth the extra $50 for a better designed compressor. It made a world of difference on mine.
You may have had good luck with remans, but if your replacing an HR6 compressor the new design eliminates the weak point in the originals. It's worth the extra $50 for a better designed compressor. It made a world of difference on mine.
WHY is everything a pissing contest with you?
What is your problem?
You have no idea about the internal design of the Four Seasons HR6 compressors. If they have incorporated any "improvements" or not. I offered my advice based on many years of installing both remanufactured AND new components, my experience overhauling Fiero A/C systems and my experience with THIS PARTICULAR BRAND.
Show us YOUR Fiero A/C overhaul thread or even any substantial contribution to this topic over the years here on PFF.
Otherwise, LET IT GO!
[This message has been edited by randye (edited 07-25-2015).]
Your the one that just turned this into a pissing contest, all I said was the new design works better since it runs quieter and smoother. I don't gave a rats ass what you use. and by the was I was a mechanic for over 30yrs.
Your the one that just turned this into a pissing contest, all I said was the new design works better since it runs quieter and smoother. I don't gave a rats ass what you use. and by the was I was a mechanic for over 30yrs.
You haven't offered ONE BIT of useful or helpful information in this thread or on this topic *anywhere*. In fact the only so-called "information" you have given out is WRONG. The GM Harrison HR6 automotive A/C compressor, (just like its predecessor the DA6 and it's follow-on compressor the HR6E), has 3 pistons, NOT 6 as you claim.
quote
Originally posted by tebailey:
Do not get a reman, spend a little extra and get a new one. The new ones have dowel pins to keep the case aligned and have 10cyls instead of 6. My first reman lasted less than 50 miles, the new one has been blowing cold for a year and draws less on the engine.
Want have a pissing contest about that too? Fine, just show us YOUR parts book or a schematic or *anything* of this GM Harrison HR6 compressor that you claim to have 6 and now 10 pistons. I would like to see it.
You have done NOTHING in this thread to offer ANY real helpful, correct information. NOTHING to answer sricka01's questions or offer him any actual help.
Just a pissing contest and WRONG information.
No wonder a lot of long time members here that have gone to the trouble to do this kind of work, take photos, document procedures and share it freely with others are LEAVING this forum.
It is now loaded with a lot of jackwagons that KNOW NOTHING, CONTRIBUTE NOTHING and argue with everyone.
[This message has been edited by randye (edited 07-26-2015).]
Now I see why no one responds to you and you can add me to the list since your opinion is always right no matter what. Sorry if I devalued your stock in 4 seasons. Go find some one else to fight with since this is the last response you'll get from me. I'll stick With new compressors, you can stick with the remans.
Now I see why no one responds to you and you can add me to the list since your opinion is always right no matter what. Sorry if I devalued your stock in 4 seasons. Go find some one else to fight with since this is the last response you'll get from me. I'll stick With new compressors, you can stick with the remans.
Great, but I still want to see this mythical 10 cylinder Harrison HR6 compressor of yours.
[This message has been edited by randye (edited 07-25-2015).]
Try to put a very small dab of silicone or RTV sealant on one side of the switch on the outside of the plastic housing where it will NOT interfere with the metal to metal contact of the plug. Connect it back up and let it set for a few hours to cure. Make sure both surfaces, (switch and plug), are CLEAN and OIL FREE. Wipe off with alcohol before applying the sealant. It should only require a tiny spot, approx. the size of a #2 pencil eraser, or less to hold the plug in place and still be able to pull it off later if the need arises.
Thank you very much Randye! I will try this RTV method. Very simple idea!
Great, but I still want to see this mythical 10 cylinder Harrison HR6 compressor of yours.
Randye, I looked up old receipts for my two 88 GT's. The first compressor was "compressor works" from Autozone part #620248. I don't remember the unit having any ICE32 in it, it was bone dry. CompressorWorks is owned by FourSeasons anyway. In the description, they state it has 10 cylinders and also uses PAG46. Well I used PAG150 (I hope that won't be an issue.) http://www.autozone.com/coo.../841638_145609_3513/ Each unit is assembled with ICE32 lubricant to reduce internal friction promoting enhanced system performance and longevity Our 10 Cylinder design runs quieter and more efficient than the original equipment 6 Cylinder design It also incorporates dowel pins to prevent case twisting - a common source of leaks in the original equipment design Each unit is individually leak, vacuum and pressure tested prior to packaging to ensure leak free performance Uses PAG 46.
There's a good rebate on this model right now: Rebate details: AUTO1168 AutoZone Rebate. Purchase one New Compressor, one Accumulator or Receiver-Drier and one Expansion Device between 06/30/15 – 07/27/15 and receive a $40 AutoZone Gift Card.
Autozone probably has a really bad description. I guess it really doesn't matter what compressor it is considering both freeze me out to 38*. All the posts from Randye, RWDPLZ, and Marvin were extremely helpful in the teardown, flush, HNBR oring explanation about captured/noncaptured, vacuum, and charging. Saved me alot of money and gave me new tools like curved wrenches, manifold gauges, and vacuum pump from HF.
I checked CompressorWorks website and they only list NEW category for HR6 even though AZ says its reman'd. http://eaccess.smpcorp.com/ecataloglite/CWI/ They also say to use PAG150. I searched all over and everywhere for GM HRx version, to use PAG150. So right there, AZ website has two wrong details.
[This message has been edited by sricka01 (edited 07-26-2015).]
Yes they do have bad descriptions. Here in the Southeast the AutoZone stores and Advance Discount Auto stores have merged at the corporate level, and although they still have separate stores, they maintain common warehouses and it appears they have the same fools running their websites. I have noted a great many descriptions for products applied incorrectly on both websites. I never use their website information as authoritative for anything more than their own part number and a price.
I'm happy if I have been even marginally helpful and I hope the RTV works for you. It's not the optimal solution, but then compressor switch plugs aren't something one normally disconnects regularly.
[This message has been edited by randye (edited 07-26-2015).]
Good info worth a positive. : However all HR 6 compressors do not have a high pressure switch. The 4.9L version comes to mind. For these applications a switch on an external switch port can be used.
The 4.9, as installed in a Fiero by TFF, does not utilize any pressure switches. At all. Mine worked fine (for probably 8 years) right up until it didn't. Coming back from Indy, I blew out a high pressure hose at 80 MPH. Was pretty spectacular. Thought I had blown an engine, based upon the noise and smoke. When I rebuilt the A/C system (complete flush, and new accumulator and compressor) I added a high pressure switch. I did not add the low side switch, as it seemed to be redundant to the pressure/cycling switch in the front. (Yes... I understand the difference, and am willing to put up with it.)
------------------ Raydar 88 Formula IMSA Fastback. 4.9, NVG T550 Praise the Lowered!
