New Member trying to solve an AC issue

Hello, new Riv owner here. Its a 1995 with around 120,000mi. Any way, the AC is not working. It has enough freon in it, I hooked up the gauges and there was plenty of pressure. The clutch will not engage on the compressor, even when jumping the pressure switch. At first I thought it may just be the clutch is broke, but I unplugged the connector for the clutch and tested it for voltage while jumping the pressure switch. It was at 0.2 volts. I was expecting it to be at 0. I then checked the relay and switched it with the horn relay which works, and no difference. I pulled the relay slightly out so I could check voltages at each pin. All pins were reading 14.4 volts with the engine running, except one of the 3/5 pins, which is the switch. I tried to jump that and it made no difference. I'm really stumped. I don't think the clutch is bad because I can't get voltage at the clutch wiring.
Also, I noticed the radiator fans would run on as the engine got hot when the pressure switch was unplugged. If I had a jumper wire on it or plugged it in the fans would stop running on high.

Anyway, hope that's not too confusing

Quick recap
AC pressure, low side is around 36psi
Jumped pressure switch, clutch does not engage
No power at the clutch switch.
Fans stop when pressure is jumped or plugged in.

Thanks for any help you can provide

is your ambient air temp sensor working?

btw engine fans should cut on around 220*F, which is a pretty hard temp to reach unless there is something wrong. they should both run when the a/c is turned on though.

I am assuming you checked the refrigerant pressure with the a/c on full cold. what was the ambient temp and what did the high side show?

The ambient temp on the dash showed around 84 when I checked it which would be correct at the time. I don't remember what the high side was for sure, but it wasn't anything that stood out to me. I've played with AC systems before, both auto and house, so its not a new game to me. I did some more checking after my initial post. The relay will show continuity between the clutch wiring and the relay. Voltage comes in the pins where their suppose to.

What else would be preventing the clutch from receiving voltage to turn on? The low side pressure switch is working and sensing pressure. I confirmed it by checking resistance on the switch it self which showed 0 resistance. Jumping the wires don't turn on the compressor like it should either.

The HVAC controls are set to fan on high, temp set for 60

The fans turn on high when the low pressure switch is disconnected and the circuit is open.


When I bought it the other day I was hoping for a leak. There usually easy to find and replace parts, vacuum and recharge.

I checked the pressures on my gauges again this morning. I must have missread the low side. It reads 26psi. High side reads about the same, which makes sense because the compressor is not running.

Does anyone have a wiring diagram, or can you explain to me the way the circuit works from the HVAC controls?

System has pressure, the low pressure switch appears to be working. No power to the clutch switch. How do I check the high cut out switch?

Spin wrote:

Hello, new Riv owner here. Its a 1995 with around 120,000mi. Any way, the AC is not working. It has enough freon in it, I hooked up the gauges and there was plenty of pressure. The clutch will not engage on the compressor, even when jumping the pressure switch. At first I thought it may just be the clutch is broke, but I unplugged the connector for the clutch and tested it for voltage while jumping the pressure switch. It was at 0.2 volts. I was expecting it to be at 0. I then checked the relay and switched it with the horn relay which works, and no difference. I pulled the relay slightly out so I could check voltages at each pin. All pins were reading 14.4 volts with the engine running, except one of the 3/5 pins, which is the switch. I tried to jump that and it made no difference. I'm really stumped. I don't think the clutch is bad because I can't get voltage at the clutch wiring.
Also, I noticed the radiator fans would run on as the engine got hot when the pressure switch was unplugged. If I had a jumper wire on it or plugged it in the fans would stop running on high.

Anyway, hope that's not too confusing

Quick recap
AC pressure, low side is around 36psi
Jumped pressure switch, clutch does not engage
No power at the clutch switch.
Fans stop when pressure is jumped or plugged in.

Thanks for any help you can provide

This not-so-Quick reply is a bit rambling but I hope it triggers a thought that gets you fixing your system:

- it's a 16 year old car and might have a hidden break in wiring under the insulation, typically near a crimp or swage that attaches terminal pins to the wires -- stuff may test OK when probed and not work when not probed. Common problem in old wiring in high-vibration (automotive) environments.
- I don't understand how you know what the pressures are if the compressor's not engaged, and if you have time could you point me to an explanation? In my experience there is little I can do with a static pressure reading besides confirm that there is refrigerant in the system. I don't know what low-side pressure has to be on this system to keep it running (it is an orifice tube system and runs or not based on a reckoning of low-side pressure) but I am thinking 85-90 PSI means there *is* refrigerant in it but whether it's enough or not no way to tell. 70 PSI I am thinking would be low. My understanding is that in most cases a static pressure of 45 PSI or so on the low side is the minimum needed for an R-134 system to operate at all. At 26 PSI I think you might well be inoperable.
- if you have a terminal that is supposed to be at 0 volts and it shows a voltage, odds are you have one or more bad grounds elsewhere
- You might already have tried asking the previous owner (PO) what they already attempted (if they are available)? If you have not, now that the transaction's done you might be surprised at their candor. On the other hand if the PO is a deceased or incapacitated relative you have my sympathy and understanding, been there. You don't have to believe what you're told, but no matter what you're told it will be informative.
- do you think there might be a controls problem? More than once cars I've seen, a connector has come off behind the dash at the HVAC head. And if you look carefully more often than not there is evidence of a collision and repair - paint overspray on the weatherstripping or pieces of interior trim that are not as faded with age or some such. And such-and so. So - have you checked the connections to the AC control head? Can you get a spare head to swap in?
- wondering what evidence you have that the clutch works - that is, depending on where the short in the coil is you might show some resistance (indicating an OK coil) but it might be not enough of the windings get energized in order for it to generate enough EMF to engage. By the way the clutch and coil are separate, the coil is like a $50 to $75 part
- if you replace the compressor be sure to flush the system well. By the way a cheap way to get a good compressor is to have a junkyard where they pull parts for you use the Hollander interchange to get you a 'fresh' compressor off a car that's just come in on which the AC was known to work. Point is that many cars are junked because they can not be readily and profitably sold, not because they do not work - and people do not necessarily junk their cars over an AC failure, there are other reasons.
- I wonder how long you tried to run the system jumpered, or if someone did it before you showed up and partly burned the clutch. See, to speed up the charging process, as you know many technicians will jumper the cycling clutch switch to hold the clutch in and get the compressor to run steady while adding cooling gas... but they have to be very careful not to run the system jumpered for too long. Reason: when low side pressures are too low, the evaporator will start to freeze which starves the compressor of oil and causes failure from "cooking" the seals. What I don't know is whether this jumpering would push an already marginal coil over the edge to failure.
- do you know about this site? (LINK)

The weird thing about the Riviera is that if you keep using the AC, the AC seems to run and run and run. If you quit using the AC for whatever reason the AC seems to fail very quickly from myriad causes.

Good luck finding and fixing the problem.

Thanks, It appears my system may be low. I just got done checking a chart for the static pressure of R134a and I'm at about half of what it should be for the temp this morning. I'll vacuum and check for leaks and add new freon.

The previous owner is in the army and hadn't driven the car for over year. This was his second vehicle and didn't get driven much before then. He said the AC worked when he parked it, and I believe him. He was pretty honest about everything else.

Spin wrote:

Thanks, It appears my system may be low. I just got done checking a chart for the static pressure of R134a and I'm at about half of what it should be for the temp this morning. I'll vacuum and check for leaks and add new freon.

The previous owner is in the army and hadn't driven the car for over year. This was his second vehicle and didn't get driven much before then. He said the AC worked when he parked it, and I believe him. He was pretty honest about everything else.

...I get it better now. Do you think the seals (compressor) may have dried out from nonuse? That is, even if you get it running you may have to replace anyway?

I don't have the specs here, but 26 PSI while off sounds low. If the system detects low pressure (and thus low on freon), it won't engage. Will the clutch engage if you jump it directly?

The fans are coming on with the pressure switch disconnected because it thinks it's seeing pressure too high. If you turn the AC off on the dash (econ/vent or off) the fans should cut off too.

I did some testing before I left for a business trip. I think its the coil for the clutch is bad. I will try to jump that directly to 12 volts to be sure when I get home, engine will be off. I finally had 14.4 volts at the wiring for the connector for the coil with the engine running, I my have had a bad gound on my meter last time I checked.

I'll report back on Thursday night what I found. If that is not the problem, it would be a bad wire or a bad HVAC control.

Problem solved. There is no way the AC worked before I bought it. I jumped a hot and ground to the clutch and the coil worked. Measured power at the plug for the coil with the AC on. Got a mirror to see inside the plug and one of the prongs were bent over. I straightened it and it works now.

Spin wrote:

Problem solved. There is no way the AC worked before I bought it. I jumped a hot and ground to the clutch and the coil worked. Measured power at the plug for the coil with the AC on. Got a mirror to see inside the plug and one of the prongs were bent over. I straightened it and it works now.

NICE piece of work. Boy was I stumped.

Albertj

Hey ,how many cars/members do we have here with working ACs haha....mine ain't working either.

AC isn't that hard of a system to understand. You just need to tools to fill/check/evacuate the system, and the knowledge of how it works

I got stumped because I should have had power when I was showing none. I got too excited there and didn't check to make sure I had a good ground on my meter.

Once I had time to recheck that and then check to make sure the clutch was working there was only one place it could have been.