I searched but could not really find much on the forum.
Does anyone know why there are so many various choices for all of the switches associated with the 1988 ac system?
I read somewhere that one of the switches on the compressor on the earlier models was moved to one of the lines on the later.
When I look at sites that sell ac parts and list an 88 Fiero there must be 6-7 different switches.
My question is: How many total switches are used, what are their names and how do you determine the right ones?
Thanks, Mike

What engine? 84-85 4 cylinder and 85-88 V6 all had the same switches (DA6 and HR6 compressor), and 86-88 4 cylinder had different switches (V5 compressor). I did a writeup on the DA6/HR6 compressor switches:

https://www.fiero.nl/forum/Forum2/HTML/117640.html

In addition to those two in the back of the compressor, the DA6/HR6 also has an accumulator-mounted pressure cycling switch.

The V5 uses the same high-pressure cutoff switch, but instead of the low pressure fan switch, it has a low pressure cutoff switch, which is normally closed, and opens if pressure falls to or below 8psi.

[This message has been edited by RWDPLZ (edited 06-22-2012).]

Sorry, mine is a 2.8 in a 1988 GT.
Here is what I mean.
If you scroll down this page it has about 8 different switches.

http://www.ackits.com/merch...de=Pontiac88Fiero2-8

But, if I go with the nymbers you provided I should be good to go.
Thanks

[This message has been edited by TXGOOD (edited 06-22-2012).]

The ones in the link above are the ones you want then, Santech part # MT0671 and Santech part # MT0678, will replace the ones in the compressor. The 4 Seasons part #'s are 35967 and 35961, respectively.

That`s what I will do, just go with tried and true.

Ok I started ordering parts for my AC upgrade and I`m going with the Santech switches RWDPLZ mentioned, but I still don`t have a number for the switch that goes into the accumulator/dryer. Anyone?
RWDPLZ, did you replace the switch for that?

[This message has been edited by TXGOOD (edited 07-05-2012).]

Santech MT0207, Four Seasons 35751, or AC Delco 15-2151. Usually the old one has an adjusting screw between the terminals, make sure it comes on at 25psi on the low side if you're using R-12, or 21psi if using R-134A. Replacing this switch if it turns out to be bad isn't a big deal, since it goes on an accumulator port that has a schrader valve, so you don't have to discharge the system to replace it.

Ok thanks, + to you.
Mike

FOUR SEASONS Part # 36674 for r134a

So I just got as new 4 seasons compressor for the 85. It has NO switches in it, just what appear to be steel blanks in the switch ports, held in with clips.
Am I correct in assuming that I need to remove these blanks and install either new or the old compressor switches (assuming I can get them out)?

------------------
Anything I might say is probably worth what you paid for it, so treat it accordingly!

Dave

www.ltlfrari.com

Yep, remove the clips with snap ring pliers, pull the plugs out with normal pliers. Should already be o-rings in there pre-installed and oiled, coat with more oil if they're dry. Put in new switches, replace snap-ring, that's it!

I just about have all of my parts for the R134A switch.
Compressor, accumulator, variable oriface tube, two switches in compressor and one in the accumulator and the seal kit.
I`m still debating on whether or not to replace the hoses but I guess since I have all other new parts it would probably be a good idea to replace them too.

What I found strange is that I ordered the Santech switches through Autozone and on their website if you put in just the switch number it comes up as it will replace the switch in my Fiero, but when I entered the kit with the pigtail it said it wouldn`t fit.
I guess it has something to do with the pigtail not being the same as the original.

[This message has been edited by TXGOOD (edited 07-06-2012).]

I replaced everything but the accumulator. I tried the vacuum before I switched it out. It was wasted if you can't get a vacuum . Just replace it after you know you have all the seals and lines holding. Then vacuum it down once more.

Might save you around $30.00 for the accumulator and amount of necessary oil. It did me.
-Joe

[This message has been edited by josef644 (edited 07-07-2012).]

Joe, my car still hasen`t been converted over to 134A so I wanted to get everything new.
If I lived in a climate where there is not much summer I might fudge, but here in Texas I want to make sure I don`t have a weak link somewhere.
Mike

You should replace the accumulator any time the system is opened, or if it's more than five years old. The desicant absorbs moisture very quickly. An over-saturated desicant bag can rupture and spread a nasty mess throughout the system. The old R-12 desicant isn't R-134A compatible, either, but the new stuff is compatible with both R-12 and R-134A. Accumulators are a lot cheaper online than in stores for some reason, too.

Also, be sure to drain the old oil and measure it, from the pipe, and by drilling a hole in the bottom of the accumulator and draining it. Will probably contain 4oz or so.

quote Originally posted by TXGOOD: Joe, my car still hasen`t been converted over to 134A so I wanted to get everything new. If I lived in a climate where there is not much summer I might fudge, but here in Texas I want to make sure I don`t have a weak link somewhere. Mike

quote Originally posted by RWDPLZ: You should replace the accumulator any time the system is opened, or if it's more than five years old. The desicant absorbs moisture very quickly. An over-saturated desicant bag can rupture and spread a nasty mess throughout the system. The old R-12 desicant isn't R-134A compatible, either, but the new stuff is compatible with both R-12 and R-134A. Accumulators are a lot cheaper online than in stores for some reason, too. Also, be sure to drain the old oil and measure it, from the pipe, and by drilling a hole in the bottom of the accumulator and draining it. Will probably contain 4oz or so.

I agree....... But you can check it for vacuum leaks with out changing the accumulator. After you know that it is all good, switch out to the new accumulator and vacuum it down again, before you charge the refrigerant. Make the accumulator the last thing you replace before you charge. If it doesn't hold a vacuum, you just wasted $30.00 worth of parts and oil. This can get expensive real quick.

[This message has been edited by josef644 (edited 07-07-2012).]

Thanks Flimbob, I was just going over this thread again and caught your comment about the Four Seasons clutch cycling switch being the 36674 and I think RWDPLZ must have thought I was talking about the R12 replacement because the Four Seasons number he gave me was for the R12 and the one you gave me was for the R134A
I`m going to call SanTech and find out what their number is for the R134A conversion.

The R-12 switch can be adjusted to work with R-134A, or like flimbob posted, you can buy the switch that's already set up for it.

Now I`m really confused. I`m not doubting anyone`s word in this post I`m just looking for clarification.
According to PWDPLZ the low-pressure switch is used to turn the radiator fan on when the correct pressure is reached. I was under the assumption that the fan ran all of the time when the AC is on. He says that the correct pressure for the low pressure switch is 280. On Four Seasons website under an 88 Fiero the low pressure switch that they suggest is a 35756 which has a cutoff of 25-26 PSI but in Randye`s AC repair build he used a 35969 which has a cutoff similar to what`s stated above of 170-240 PSI.
This is from the Four Seasons website on the low pressure switch.
The high-pressure switch should be closed below 400-psi, which
will allow the signal to pass on to the low-pressure switch. If there is sufficient refrigerant pressure
(minimum of 40-psi) at the low-pressure switch, the signal will pass through the low-pressure
switch where it will be received by the PCM. After the PCM receives this signal, it processes this
information and checks to see if all other input sensors are within specifications before proceeding.
If everything passes, the PCM will supply a ground signal to the compressor clutch control relay
which will then engage the compressor clutch.

My question: Is the low pressure switch`s function to turn on the radiator fan or is it to make sure the compressor clutch does not engage unless the pressure is at 40PSI or above making sure there is enough refrigerant.

Edit: I just talked to a tech at Four Seasons and he said that the low pressure switch is to make sure that you have enough refrigerant in the system for the clutch to engage.
thus using the lower pressure 35756 switch. That the reason the fan runs all of the time with the ground connected is that it is a fan switch and with a rating of that high of pressure the fan would run all of the time. He may be wrong I guess but it makes sense to me.

[This message has been edited by TXGOOD (edited 07-13-2012).]

quote Originally posted by TXGOOD: Now I`m really confused. I`m not doubting anyone`s word in this post I`m just looking for clarification. According to PWDPLZ the low-pressure switch is used to turn the radiator fan on when the correct pressure is reached. I was under the assumption that the fan ran all of the time when the AC is on.

Yes, it is redundant. I think their thinking here was, if the for some reason the AC control head doesn't turn on the fan, the low pressure fan switch will turn it on if the pressures get high enough.

quote My question: Is the low pressure switch`s function to turn on the radiator fan or is it to make sure the compressor clutch does not engage unless the pressure is at 40PSI or above making sure there is enough refrigerant.

On YOUR car, it's to turn on the fan. I think the confusion is coming in their lazy websites mixing up the V5 and DA6/HR6 switches. The V5 uses the same high-pressure cut-off switch, BUT instead of the low pressure fan switch, it has a low pressure cutoff switch, which is normally closed, and opens if pressure falls to or below 8psi.

The pressures for the switches are in the 88 service manual. Page 1B-4:

quote High-Pressure Cut-Off Switch The high-side, high-pressure cut-off switch in the rear head of the compressor, is a protective device intended to prevent excessive compressor head pressures and reduce the chance of refrigerant escape through a safety relief valve. Normally closed, this switch will open the circuit at approximately 2700 kPa (430 psi +/- 20 psi) and reclose the circuit at approximately 1379 kPa (200 psi +/- 50 psi)

That is why I picked the one I did, it most closely matched the OE specs. 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. The Four Seasons equivalent, 35961, has the same specs, according to their website.

The specs are also on the Air Conditioning: Compressor Controls wiring diagram, on page 8A-64-0: Here, they give the V5 and DA6/HR6 pressures on the same diagram, split up by L4 or V6 VIN 9 engine. The high-pressure cut-off switch has the same specs for both compressors, opens above 425psi. The V4 low pressure cut-out switch opens below 8psi. The pressure cycling switch opens below 24 psi (remember this is an R-12 system, now it would be 21psi with R-134A).

The DA6/HR6 low-pressure fan switch is on the fan circuit diagram, page 8A-31-0: The low-pressure fan switch is bottom center of the diagram, and is closed above 280psi

quote On Four Seasons website under an 88 Fiero the low pressure switch that they suggest is a 35756 which has a cutoff of 25-26 PSI but in Randye`s AC repair build he used a 35969 which has a cutoff similar to what`s stated above of 170-240 PSI.

As you can see from above, this suggested switch 35756 is simply incorrect. The switch from Randye's thread, 35969, is the low-pressure fan switch, it is on 240, off 170, which is still within OE specs, though this particular part number is for just the switch without the pigtail, which is necessary if you're updating the wiring at the same time.

quote The high-pressure switch should be closed below 400-psi, which will allow the signal to pass on to the low-pressure switch. If there is sufficient refrigerant pressure (minimum of 40-psi) at the low-pressure switch, the signal will pass through the low-pressure switch where it will be received by the PCM. After the PCM receives this signal, it processes this information and checks to see if all other input sensors are within specifications before proceeding. If everything passes, the PCM will supply a ground signal to the compressor clutch control relay which will then engage the compressor clutch.

What is being described there is how the V5 compressor works, EXCEPT their 26 on 25 off pressures of that switch will not work as originally intended with a V5 compressor, since the V5's original low pressure cut-out switch cuts out at 8psi. In their description, the compressor clutch is controlled directly by the ECM, where on our cars it's controlled by the switches. They appear to have been copy/pasting specs from other cars, and assuming it'll work with ours.

Looking at their catalog, they don't offer a switch that cuts out at 8 psi, in fact the 25 psi cut-out seems to be the lowest they offer, and would be their closest replacement. So if you have a V5 compressor, you'd want to use 35756 and 35961 to replace the orignals.

[This message has been edited by RWDPLZ (edited 07-13-2012).]

I also contacted Santech and they said that their clutch cycling switch MT0207 is set at 25PSI which is good for R12 or R134A.
I told them about the R134A being closer to 21 PSI but they didn`t think it mattered.

quote Originally posted by TXGOOD: I also contacted Santech and they said that their clutch cycling switch MT0207 is set at 25PSI which is good for R12 or R134A. I told them about the R134A being closer to 21 PSI but they didn`t think it mattered.

It does matter, and I'm sure they don't care.

Thanks for your help RWDPLZ .
I guess I will just replace the accumulator switch I got from Santech with the Four Seasons which come with the lower rating.
Just out of curiosity, considering the switch that Four Seasons and Oreilly both list as the lower pressure switch on the low side of the compressor backs up the control unit`s activation of the fan would it really matter what pressure the low side switch is?

IF the system is working properly, you don't even need the switch. It's just a redundant safety device. I would just use one within OE specs, the purple one I posted the number for, or the gray one Randye posted. Speaking of colors, sometimes they do change the colors, so the part number is a better indicator of pressures than the switch color.

Well I finally got my AC system all put back together and I ran the vacuum on it for about 50 minutes and it`s been sitting for about an hour. So far so good.
I`m going to let it sit overnight before charging it. It was in bad shape as someone had installed a bolt in the passenger side of the bracket and it hadn`t seated and was rusty so I had to take the entire bracket off with the compressor to get the bolt out. Also, I broke the bolt off that holds the block to the lines that run up to the front, so I had to rebuild that part, including the rubber shoulder bolts that hold the bracket in. I installed an inline filter in the line between the condenser and orifice tube. I thought that I had received the wrong accumulator until I realized that the top, where one of the large lines attaches, can turn enabling you to adjust it to where you want. It was a learning experience.

[This message has been edited by TXGOOD (edited 07-14-2012).]

AC blowin cold.
Thanks everybody for all of the advice.
The only difference I had was that on both of the 2-wire switches I hook the ground up to both and they work fine.
I know that others have had to disconnect the ground on the low side pigtail for the fan not to run all of the time, but not mine.
Mike

quote Originally posted by TXGOOD: AC blowin cold.

Awesome!

quote The only difference I had was that on both of the 2-wire switches I hook the ground up to both and they work fine. I know that others have had to disconnect the ground on the low side pigtail for the fan not to run all of the time, but not mine.

If it's wired correctly with the correct switches, it should work just like yours is.

I have one more question.
When I moved my car there was a small L shaped rubber tube under it and after looking at the shop manual I found out it is the blower motor cooling tube.
I guess I knocked it off when I removed the spare tire tub.
What exactly is that tube for?

[This message has been edited by TXGOOD (edited 07-16-2012).]

Cooling the blower motor if you look at the way it's hooked up, it blows (a tiny bit) of air onto the motor itself.

Here's a picture from my car:

[This message has been edited by RWDPLZ (edited 07-16-2012).]

quote Originally posted by RWDPLZ: ... if the for some reason the AC control head doesn't turn on the fan, the low pressure fan switch will turn it on if the pressures get high enough.

That is correct ... except that the AC control head doesn't turn the fan on when you select "Defog." In that case the AC high-pressure fan switch is the only way (other than high coolant temperature) to turn on the radiator fan.

Thanks guys.
I have bigger problems than that.
I have a leak because yesterday it was cooling good but this morning it wasn`t.
It does have enough pressure to turn the compressor on but it has leaked some of the refrigerant out.
Fortunately it is up in the front where I don`t have to scrounge around under the car.
I don`t have my gauges on me but I`m going to check it when I get home.
I can`t see because of the spare tire hub, but I suspect it may be the fittings on the inline filter which is just under the tub.
Dang, and all of that work this weekend.

Well that sucks. Did you add any UV dye to the system when you charged it? That would help narrow it down quickly.

quote except that the AC control head doesn't turn the fan on when you select "Defog."

Why would you want the radiator fan to be on if you're trying to defog the windshield?

[This message has been edited by RWDPLZ (edited 07-16-2012).]

RWDPLZ there was dye in the ester oil I put in and this morning there was dye in the spare tire hub right under the high side line running to the orifice tube.

You know it sort of sucks (no pun intended) that when you pull a vacuum on the system it does remove moisture from it and if it holds a vacuum its probably good to go but it doesn`t seem that rules out any leaks that might develop when it`s subjected to the high pressure of the compressor actually running.

[This message has been edited by TXGOOD (edited 07-16-2012).]

That is precisely correct, that's why professionals use dry nitrogen to pressurize the system and check for leaks. No leaks after vacuuming down the system and leaving it sit for a while is a good indicator, but not foolproof.

If you know where the leak is, have the system evacuated by a shop on your way home, fix the leak, and try again.

Well, I`m hoping that I found the leak.
The schader valve in the high side port adapter was a bit loose.
Which would make sense as the dye I saw on the tub was right below that.
I`m hoping that is all it is because I made sure all of my fittings were tight.
I just missed that one.

Mike where did you get your in line filter?

-Joe

[This message has been edited by josef644 (edited 07-16-2012).]

Joe, I got it from here.

http://autoacrepairs.com/ac_in_line_filter.htm

I recharged my system and I will see if it will leak down again.
I think I have it sealed now, but only time will tell.
I think it had gone completely empty and I put two 12oz cans but I think it might need a bit more as the accumulator and tubing is getting a bit icy.

quote Originally posted by RWDPLZ: Why would you want the radiator fan to be on if you're trying to defog the windshield?

Because selecting "Defog" turns on the AC, to remove moisture from the air being directed onto the windshield ... whether you want it or not.

Ok, I lied above when I said one more question.
I think I have my leak fixed but I was wondering about a couple of things.
When I turn my AC from norm to max it sounds like the fan is blowing like heck but there doesn`t seem to be much more air coming out of the vents.
Also, when driving my car last night between hearing the cooling fan up front and the compressor right behind me it seemed that the inside of my car seemed loud.
I uaually have the radio going, but last night I was especially listening for any noises.
Is it usual for the cabin to be pretty noisy with AC going?