quote Originally posted by Matthew_Fiero: one of the fill points?

The low side is the fill point but it is one of the hose attachment point if you put gauges on there. Unless you are hooking up gauges though there's really no need to touch the high side port.

quote Originally posted by ltlfrari: I did something similar on my DOHC but I'm not sure I got the correct fitting for the sensor to screw on to. It was close but not perfect.

did it still work?

MY system had so many leaks that that one was the least of my worries and since the car is no more guess I'll never know the real solution

LOL get this..

I take my Fiero hose in, and show him a few of these pictures and I bought the switch and brought that in two.

Hes said, and I quote: "You want me to crimp the V5 fitting on your a/c hose and tap a fitting on? I don't have time for this s**t!!"

Thats like going into a Tire shop and him saying: "You want me to take off the tire AND patch it!?"

Lets keep searching. We will find a solution. Perhaps Darkhorizon has the answer in looking for the A/C hose with the manifold that contains the high pressure switch. However, is this switch compatible with the GTP switch? Are the pinouts the same and will the GTP connector connect to it. Will this manifold fit the GTP compresor? I know that on my series III the 2006 A/C compressor is like a V5 but still different. It uses a different size hose flange than the earlier units.

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Its a 3 wire switch I am sure I have a connector for it somewhere.

bump

I believe that before we move further ahead, we need to understand the type of signal that the high pressure sensor feeds into the GTP PCM. Is this sensor just a switch that instructs the PCM to turn on the A/C when the pressures is within a certain range or is the sensor output a variable resistance used for a monitoring and control function used by the PCM to regulate the cooling. Then what is the purpose of the three pins and how are they connected? Will a pressure switch on the high port supply the needed inputs? The where do the two pins connect to? Lots of questions need to be answered.
On the wiring schematic I only see one pin where the pressure sensor connects to the PCM. so I will do more research before a solution can be offered.

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

probably would have been better to buy a Fiero compressor and put a different pulley on it :S

I believe its just to tell the PCM when to idle the car higher to prepare for the initial load of the compressor. But, I thought thats what the plug on the compressor itself is for..

What does the connector on the compressor do compared to what does the switch that needs to be added do?

[This message has been edited by Matthew_Fiero (edited 05-11-2008).]

I believe it's a sensor, not a switch.

After considerable consultation with the experts this is what I discovered about the late Grand Prix A/C system that many of us are trying to adapt to our Fieros. With thanks from the automotive A/C bulletin board guys I will share the following.
The high pressure switch is both a safety switch and control sensor. While it has NOTHING to do with the controlling the cycling of the compressor. It's main job is to disengage the computer if the high gets too high and could damage something and keeps it on if the pressures are within range. The 3-wire transducer measures system pressure- just like an oil pressure sensor does....it tells the PCM to energize the compressor if system pressure is above 47 psi--- to turn on the coolant fan(s) when system pressure is above 175 (low speed) and 225psi (high speed)-- and to shut off compresor if system pressure exceeds 425psi--- and turn it on again when it drops to 300psi....and increaase idle speed whrn the comprrssor is on. so this transducer is much more powerful than a simple switch because it can do so much more...

These late GM systems use a variable-displacement compressor model V7CVC so there is no low side cycling switch like on the Fiero. The amount of "pumping" is controlled by a pressure sensor piston system in the compressor. Since computers starting controlling operation of A/C units, the type, function, and wiring of sensor switches has changed significantly. On pre-computer systems, the sensor switches actually controlled the A/C system directly. Now. the switches and sensors report the condition of the system to the computer and it makes the determinations of what to do.
These is a warning given by a skilled A/C technican to observe caution when utilizing the three-wire switches and sensors that the GTP system needs These devices are powered directly by the computer system (usually 5V). Applying battery voltage (12V) to any switch or sensor pin can result in a blown computer system.
Therefore the connection to the three wire pressure sensor is +5V , ground (or low ref) , and the sensor output. Unfortunately since it is a powered sensor the 3800 PCM won't run the A/C system without it. For us 3800SC swap guys a "T" in the high pressure line that has the correct fitting for the A/C sensor to attach is the only way to run these systems. Since several different A/C pressure sensors were used, it is probably a good idea to match the sensor and the PCM year model so that a correct interface will result.

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

So if we are using the 3 pin sensor, we will not need to use the connector on the compressor itself?

quote Originally posted by Matthew_Fiero: So if we are using the 3 pin sensor, we will not need to use the connector on the compressor itself?

Not quite. The connector on the V7 CVC A/C compressor used on the 3800SC is where the clutch power connector is attached. The pressure sensor is a three wire device that takes 5+V PCM power, ground ,and provides a signal output to the PCM that tells it if line pressure is within range. It is is then the PCM energizes the compressor. This sensor also tells the PCM to set the idle, and turn on the cooling fans when certain conditions are met. In simple terms the sensor is a safety switch and sening device. Its needed to run the 3800SC A/C compressor.
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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 05-11-2008).]

But i thought it was clear only one wire goes to pcm.. where does the 2 wires go on the compressor switch? Green and black, i am assuming black to be either pcm ground or chassis ground..
I am still in the dark about where to ground what to pcm and what to chassis.

Once I get this switch done and finish the grounds on the harness, I can finally start the car after its 2 year slumbed (7 year slumber on motor)

The way I read it the green and black from the a/c compressor has nothing to do with the pressure sensor. The sensor gets a hot, ground, and wire to pcm all from the sensor. The question is where does it hook to on the pcm? Will it list that in the pin outs?

quote Originally posted by Dementia: The way I read it the green and black from the a/c compressor has nothing to do with the pressure sensor. The sensor gets a hot, ground, and wire to pcm all from the sensor. The question is where does it hook to on the pcm? Will it list that in the pin outs?

The A/C compressor clutch wires are connected to the A/C relay and ground. That is stated earlier in this post. The pressure sensor is a three pin (trinary sensor) connected to +5V, ground and the A/C pressure switch input connection to the PCM. Then there are two additional connections, one from the PCM to the A/C relay output and the other is the A/C request signal in to the PCM. Thats all the electrical connetions required to make the 3800 A/C system work in a Fiero. Again mounting the pressure switch is the mail obstacle as it requires fabrication of a fitting .

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

here are some random 98 GTP a/c wire pinouts

clear connector

22 - a/c request
27 - A/C refrigerant pressure sensor signal
39 - A/C compressor clutch relay control


The clutch coil gets grounded on the black end, and the dark green goes A/C compressor relay pin. There is a diode wired into the circuit

A/C request signal comes from the dash.

The pressure sensor gets some grey wire tossed into the mix, supplying the 5 volts mentioned earlier, black gets ground, and the pin 27 goes to the red/black wire on the sensor.

Blue Connecter PCM C1

Pin 17
Colour: grey
"5 Volt reference B" "A/C Refrigerant Pressure Sensor B, Fuel Tank pressure sensor C"

Pin: 25
Colour: Dk Grn/Wht
"A/C Compressor Clutch Relay Driver" "A/c Compressor Relay F8/86"

Pin 55
Colour: BLK "sensor ground" "(lists a bunch of other sensors, then) A/C refrigerant Pressure sensor A"


CLEAR PCM Connector C2

Pin 73
Colour: Red/BLK
"A/C refrigerant Pressure Sensor" "A/C Refrigerant Pressure Sensor C"

Thats all I got

I already had the a/c clutch wired in. My questions were on the a/c relay.
dk green/white from relay to pin 22?
black/white from relay to ground?
blue wire from relay to pin 39
The above pin outs are from darks post

Just so I'm clear on the sensor wiring:
Its the c1 pin 17, c1 pin 55, and c2 pin 73
Matt what are your pin outs from? I'm using the 98 gtp pcm. Do I go by darks pin outs?

Also Matt these next questions were non A/C related
PCM wiring-
tied all blacks to the black from temp to use pin to go into pcm (factory wiring I believe)?
tied grey's from map and tps together to use pin to go to pcm (factory also)?
reused the thicker guage black with the 4 pins for pcm/ Does this ground the pcm?
Sorry guys dont mean to make you repeat yourselves or offend anyone. Thanks

[This message has been edited by Dementia (edited 05-12-2008).]

My pinouts are for my 98GTP PCM
BUT the booklets i have are for 97GTP

Here is how it works on the 2003 PCM

All connections to the C2 clear PCM Connector

Pin 30 Gray +5 V to refrigerant pressure sensor output
PIn 27 Red/Black Refrigernt sensor signal pin in
Pin 35 Black Ground to refrigerent senor ground pin
Pin 39 Dk Green/White A/C relay control
(compressor clutch must connects to relay output and ground)
Pin 22 Dk Green /white A/C request signal from A/C switch ( probably +12V but not certain)

The above should work assuming that the refrigerent pressure sensor connector was left with all of its connections to the harness. Otherwise we will need to figure out which pin on the sensor goes where. It also assumes that the relay contacts are ready to make the connection to supply 12V to the compressor clutch when the relay control signal is sent to it by the PCM. If we need to wire everything from scratch then a total of 9 wires will need to be connected 4 to the relay and 5 to the PCM. Its actually 8 as one PCM wire connects to the A/C relay and the PCM.
Also for the A/C system to turn on, the A/C pressure sensor must indicate a pressure of 47 psi or greater. If the high side line pressure goes to 400PSI then the compressor will be deactivated until line pressure return to below 300 psi. The cooling fan activation signal occurs at approximately 175 PSI ot if the PCM senses high coolant temps via the ETS or engine temperature sensor.


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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 05-12-2008).]

Tell me where these go to and I should be good to go. I understand the sensor pin outs, but I cant find a plug that looks like that on my harness. So I will go looking
DK Blue A/C relay conrol to pin 39
Green/White A/C request to pin 22
Black/White to chassis ground or pcm ground? Theres already one black/white going from the relay to the C203

I see all of the grounds going to chassis ground.

Every single ground from every sensor to chassis?

no, just the a/c stuff we are talking about.

What about the DK Blue and Green/White on the relays? Do they go to the pins I asked about? The Dk Green goes to the A/C clutch, the black from A/C clutch goes to a chassis ground or should I change that to a pcm ground?

bump
thread die?

too bad

[This message has been edited by Matthew_Fiero (edited 05-13-2008).]

Its funny how a thread about our speaker grills being blue is more interesting then this thread..

quote Originally posted by Matthew_Fiero: Its funny how a thread about our speaker grills being blue is more interesting then this thread..

Perhaps it's because no more questions on this subject are being asked and no more answers are available.

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Why do you think there are so many tricks involved here? Make the lines, make the switch, and go charge your a/c, wire according to the spec of your swap, its not that hard of a project.

I asked about the wires in my pic and didn't get an answer. I guess I'll do what fieroflyer said and not hook'em up. PCM wont control the air. Although I would like to do it the other way.

quote Originally posted by Dementia: I asked about the wires in my pic and didn't get an answer. I guess I'll do what fieroflyer said and not hook'em up. PCM wont control the air. Although I would like to do it the other way.

The wire colors vary, and you picture does not show the orientation of the connector, so there is nothing I can say about it.

If you dont understand how a relay works by now, then go google one.... The way you hook it up is very clear if you know what wire goes to what on the relay.

I was hoping to have my a/c charged and running by now, but i've been out of town and didn't get it done before i left. i get home sunday and will try and get it working that week when i do i'll post how it all went.

Ant

quote Originally posted by Ants87gt: I was hoping to have my a/c charged and running by now, but i've been out of town and didn't get it done before i left. i get home sunday and will try and get it working that week when i do i'll post how it all went. Ant

Thats what Im waiting for

If it works, I will run your setup with the T

How come loyde from Fastfieros.com has his a/c hoses made up without the switch?

quote Originally posted by Matthew_Fiero: How come loyde from Fastfieros.com has his a/c hoses made up without the switch?

I spoke to Loyde about this. He doesn't use the refrigerent pressure switch in his installs which means that his swaps either use the Fiero rather than the 3800SC A/C compressor and/or controls or he is using the V7CVC variable displacement compressor in a cycling mode as it was not intended to be operated. I guess that you can do the swap this way but I always lean towards using the state-of-the-art stuff, rather than trying to meld 20th and 21st century technology together. Getting the A/C refrigerent pressure sensor on the high pressure line shouldn't be that hard to do. Its just that few have done it. Scott found a compressor manifold that has the fitting its just that this A/C line probably doesn't fit the late V7CVC compressor. It might fit the early (1999-2002 GTP) V7's though

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

I got the lines in the car tonight and also changed the accumulator and fixed orifice tube as well, i started to pull a vacuum on the system and ran out of time and energy so i'll finish it tommorow. i also got some pics of what i did so i'll post them as well and let everyone know how it works.
Ant