1995 Cutlass Ciera AC

[DeltaP]

1) I had the refrigerant drained (it only had 5 oz. in it). However it held the vacuum for several minutes (indicating no leak in the system).
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If the system only had 5 oz in it and then it held the vacuum for only several minutes then you have a leak! What don't you understand?

[mptc]

That was before it was recharged, which was about a month ago. Yesterday the scan tool read 101.8 psi. So there is refrigerant in the system. No pressure no refrigerant.

[Tech II]

Ok, on a cold engine, the pressure reading on the scan tool should be approx. ambient air......so if the car was not started, and the key is just turned to on, and you turn your ac on, your pressure reading on the scan tool should be close to ambient air....80F outside air, should register 80 psi on the scan tool.....

If it is, and your PCM data shows an ac request, then the next step is to check the ac clutch relay......first remove it....probe the 4 legs with a test light....two legs should be hot....the other two legs are the control circuit and the output circuit to the compressor clutch.....

If two legs are not hot, check your ac clutch fuse......

If they are, try swapping the ac relay with another relay......then start car, and see if compressor comes on......

If it doesn't, have someone feel the relay, while you turn the ac on and off....if it doesn't click, then you will have to check the integrity of the control wire from the PCM to the relay, to see if it is open...if it is not, bad PCM....

If it does click, and the compressor does not come on, then you have to check the integrity of the wire from the relay to the compressor clutch...

[DeltaP]

I might add that the clutch assy could be so worn that the gap is excessive and the magnetic coil just can't pull or hold it in.

[Tech II]

DeltaP, in post #14, he jumpered the clutch and it ran....

[mptc]

Okay....checked everything and back probed the control wire from the a/c clutch relay to the PCM and the clutch clicked. I did the same for the secondary cooling fan (which is supposed to engage when selecting the A/C). Same thing the secondary fan engaged. So one would assume a bad PCM.

But here is the deal....I have purchase 2 other PCMs. Both from a salvage yard in Wisconsin on two separate occasions. So including the original PCM, I now have 3 PCMs all displaying the same problem. What are the odds of that happening?

[Tech II]

I guess it is back to square one......

Need the engine cold first thing in the morning.....

Need gauges on the A/C system.........

Key on, engine not running.....

P0530 must not be set....if it is, clear it.....

Does the pressure reading on the scan tool, equal the pressure reading on the gauges(hi and lo should be equal)? Is the pressure close to ambient air?

If yes to all, start car....turn AC on....does the PCM recognize an AC request on scan tool?

If it does, and pressure reading is ok, then the PCM should be grounding the AC clutch relay.....but apparently it isn't.....

Now, you replaced the sensing line(red/blk) from the sensor to the PCM....

You also said you back probed the control wire(dk green/white) from the PCM to the AC clutch relay and it clicked.......so with the car running, AC requested and blower on, watch the pressure data on the scan tool.....now back probe the control wire to ground again......the clutch should engage, and you should feel cooling, and the pressure data on the scan tool should drop to 30-40 psi......does it do this? Do you get cooling? Do the cooling fans come on? Just do this for a few seconds......

If the compressor comes on, the cooling fans come on, the pressure reading is ok(30-40), then I think you have to check the integrity of that dk green/white wire back to the PCM....it could be an open wire, since you have replaced the PCM.....

[mptc]

I am back...it has been a long while. The AC is fixed. I replaced the wire from the PCM to the A/C compressor clutch relay including new terminals at the PCM side and the relay side. I also did some diagnostics on the secondary fan relay...which is supposed to engage when A/C is selected. I tested the wire from the pcm to the secondary fan relay. It showed no resistance (.000). I replaced it anyway and what do you know...the compressor clutch kicked on. I also discovered a bad crimp connection in the wire leading from the compressor clutch relay and the compressor plug. I appreciated the patience and help to a novice (at best) budding mechanic (I use that term in the loosest sense).

I do have a new question/request. I am looking to replace the battery cables both negative (which is no problem) and positive which has been discontinued. It is an unusual cable (GM 12157254). It has the wire that leads to the starter but it also has a secondary wire that splits into 3 fusible links (one leading to the ignition, one leading to the Anti lock brake relay and not sure where the other leads but shouldn't be hard to figure out). Is anyone aware of a source for that type of positive battery cable? If not is there a "work around" using a more conventional positive battery cable.

Thank you in advance for any assistance.

mptc

[Tech II]

You can get any pos bat cable of the correct length.....if the fuseable links are ok, just cut them as close to the starter as possible and add "eyelets"(aka ring terminal) to them to connect them to the post on the starter with the pos battery cable....

[mptc]

It is about 20" from where the pos. cable connects to the starter. The current fusible links are too short to cover that distance. Most of the fusible links I have sourced are about 9" long. Still too short. Is it possible to get 14 and 16 gauge fusible link wire and cut it to the length I need and then crimp the appropriate eyelets onto one end and use a 3 way connector (male and female) to connect to the ignition wire, etc.? Or just butt connect them individually?

Thanks,

mptc

[Tech II]

That should work.....

Just remember:

An electrical fusible link is a type of electrical fuse that is constructed simply with a short piece of wire typically four American wire gauge sizes smaller than the wire that is being protected. For example, an AWG 16 fusible link might be used to protect AWG 12 wiring. Electrical fusible links are common in high-current automotive applications. The wire in an electrical fusible link is encased in high-temperature fire-resistant insulation to reduce hazards when the wire melts.

[mptc]

So would you suggest 3 - 9" fusible links (2-14 gauge and 1-16 gauge) coming off the stud on the starter and then connect 10 gauge wires to each of those terminating at or close to their point of origin?

thanks,

mptc

[Tech II]

What wire size did you come up with for the circuits?

Are all 3 circuits the same size or different?

For example, if all three circuits are the same size, let's say 14 gauge, the you will use 3-18 gauge fusible links.....

[mptc]

Originally Posted by Tech II

What wire size did you come up with for the circuits?

Are all 3 circuits the same size or different?

For example, if all three circuits are the same size, let's say 14 gauge, the you will use 3-18 gauge fusible links.....

Actually 2 are 14 gauge and 1 is 16 gauge.

mptc

[Tech II]

I found a wiring diagram, it shows all three circuits being 2.0(metric)...

Are you sure? My wiring diagram could be wrong....