Wiring Diagram

I have a annoying but probably simple electrical fault with SVX Air Conditioning.

The electrical clutch mechanism is not engaging when the aircon is activated from the climate control panel.

I have traced the fault so far, but like all things I am in need of a little help.

I have traced the cable that activates the clutch back to the relay in the engine bay fuse box. When swapping relay with known good one still not working and old relay working ok in other circuit - so relay is OK.

When applying 12v to the switched side of the relay contact clutch operates and air con pump works - so pump ok and cable from fuse box (relay output) OK.

The Input to the switched part of relay has 12v available so if the relay were to operate it in turn would activate clutch.

So this suggests the fault is the coil side of the relay is not getting 12v to activate it. Comparing it to the heated seats I am seeing no volts whatsoever compared to volts when activating heated seat switches - ah ha a clue!!! But this is where I need help the wires from the relay socket disappear into the loom never to be seen again. I need a circuit diagram (or part of) to show me how the relay is wired into which loom and what colour wires its connected to. I can then at worst run parallel replacement leads to their original destination and hopefully be cool once again.

I know the system was working, and I suspect I may be the cause of the electrical fault as I have been doing a lot of work on the rest of the cars electricals which are now all OK! Typical init tho one step forward two back

Sorry its a long entry - but if anyone has a circuit diagram I would be very gratefull.


Paul.

Paul,
Just a thought, the compressor won't kick in if the coolant sensor thinks its too hot. The diagnostic procedure is in in my locker and I'll add a .pdf file on the AC. Dave

Very usefull pdf - thanks - however where is this tristate switch unit have look at front right of engine bay????

Thanks once again

Paul

I can't see anything that might be a pressure switch. Any luck with the diagnostic? D.

in the section headed COMPRESSOR CLUTCH DOES NOT TURN ON OR OFF the text refers to Trinary (triple) pressure switch. I cannot locate this on my car - do you know where it might be hiding?

Many thanks , as always!

Paul.

ps you know despite only owning the car 2 weeks and having fixed over 20 faults I really the SVX ! ps My other car is a Pontiac TransAm 1996 5.7 V8 350 bhp - not nearly as refined as the SVX!

Originally posted by PWA1X
in the section headed COMPRESSOR CLUTCH DOES NOT TURN ON OR OFF the text refers to Trinary (triple) pressure switch. I cannot locate this on my car - do you know where it might be hiding?

I saw that part. Again, I looked at mine and saw nothing like a pressure switch. Maybe someone who's been into it can help you. The diagnostic checks the sensors that can keep the compressor from kicking in. I would also reset the system. D.

[lee]

The trinary switch is located on the right (from a driver's perspective) of the condensor. Follow the tube coming out of the condensor toward the drier and the trinary has four wires.

I don't know what you got in the PDF, but if you need help tracking the problem down further, PM me....I had a long detective run with my A/C having the same symptoms. I can lead you through all the diagnosis - assuming you have a volt-ohm meter.

I have meter and a very good level of electrical/electronics ability. So no problems there.... As you can see from the original post I am sure my issue is the 12v pull up signals to the relay coils are just not getting there. Maybe its to do with the very hot weather we have here in the UK at present 30C ! (Most unusual) Or maybe more likely sensor/wiring fault...... As I see the diagram either the control unit is just not sending the signal to activate the clutch (which I think is basically pulling line to -ve). Or it is the other side of the story 12v line (which incidentally is 0v at the relay socket) which is supplied via the trinary device.

Anyway thanks for its location Ill take a peek at that today (why do these things fail on very hot days?).

Paul.

ps your offer for techinical run through is appreciated and welcomed - do you have a list you could email .. paul@3-rivers.net

[lee]

Sorry, I don't have a written list.

I think you are on the correct path. Contacts 1 & 4 should show zero resistance across the trinary switch (2 & 3 control fan speed with A/C on). Check by disconnecting the wires leading to it with the ignition off. If there is zero resistance, then the trinary is OK for compressor cut on. The problem then is probably electronic. Basically the ECM holds the white/black wire to the relay at 10-12 volts when the compressor should be off, and pulls the wire to ground when the compressor should be on - making a path to trigger the relay.

But first, have you run the internal climate control diagnostics? Press ON and AUTO as you start the car (needs daylight on the sun sensor to avoid a false error).

If that's OK, then you need to get under the dash at the ECM and check the voltage at two places, both places with the A/C switched off, and with it switched on.

Test that by checking wire #9 on the 16 pin ECM connector ( a brown wire on the end). Should have 10-13 volts with A/C on, zero with A/C off. This is the signal from the climate control module to the ECM. With zero volts on or off, the problem is probably in the climate control module. And you have to follow a different path than below.

If that's OK, then test wire #8 on the 12 pin connector (a white wire with black stripe or vice versus, I forget). Anyway, it will be second from one end of the connector. It should be 10-13 volts with A/C off, zero with A/C on.

If the second test fails, then you probably have either a bad throttle position sensor, or a faulty ECM. In my case I had a faulty ECM, and since that was the only problem with the ECM, I decided to wire around it. I used another relay to trigger ground and employed an Op Amp in voltage follower mode with the signal picked off the brown wire from the climate system to the ECM. I clipped the white/black wire from the ECM and connected the ouput of my new circuit to the white/black wire leading to the stock relay - so the trinary was still in the system, etc. The attachment shows the circuit I used if this turns out to be your problem.

I can re-explain if this isn't clear, or you haven't found the problem from my description. Just so you don't feel too bad, I had to put my car on jackstands this morning and change the inhibitor switch on the transmission - I live on the coast in Florida, so warmth and humidity are always present - it will be about 32C today.

Thank you for such an informative reply - I will go over these now. However, I suspect the answer could be so so simple..... The trinary switch is not as you describe and I suspect I may be guilty of missing the obvious... The trinary is there to check for gas pressure before activating the system and needless to say that 'switch' is open circuit, which could indicate a broken switch BUT of course its telling us the gas pressure is too low isn't it! So on this assumption if I push the inner of the filler valve what do I get NO not a loud hiss and rush of gas but a half second little sss and thats it - repeated presses no hiss no nothing - Gosh how could I be so silly to have missed the obvious - it is out of gas!!!!!

Yours somewhat embarassed Paul.

ps like the circuit diag though - clever!

[lee]

best of luck, now you get the "fun" of finding out where the leak is at.