Low budget SAAB Viggen AC Reinstatement

You should know what this is. If not, you probably roll your windows down a lot.
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Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Low budget SAAB Viggen AC Reinstatement

Post by Fast_Ed »

The SAAB's AC failed right around 2011, about when I discovered the oil pressure issue. It turns out that these may have been related, in that the low speed fan resistor can fail and result in both of these issues.

If only the car had a real temperature gauge, this would have been obvious. At any rate, the low speed fan is supposed to be engaged when the AC Is running. With no working low speed fan, condenser temperature, and therefore pressure, can get very high, causing various pieces to leak. Refrigerant escapes, and the system goes from working poorly at idle/traffic (poor condenser cooling) to never working.

My hope is that this is the result of failed O-rings. However, my plan forward is this:

1. attach manifold gauges and check for refrigerant. I expect there will be none.
2. Run car with AC on max, and short the low pressure switch on the system to determine if the compressor clutch works. I will also be able to see whether the compressor is very noisy. If the compressor fails this test, Rockauto sells a GPD compressor for about $100. This will be a tempting replacement for this project. The Four Seasons one is $200. I can't find anything bad about GPD online...
3. Check system for leaks by pulling a vacuum. If it is not leaky, and the compressor is good, then this could be a very cheap job. I would just replace the receiver/dryer and charge the system. Maybe a new expansion valve? They are only $20...

If it is leaky, I will need to determine where it leaks. My guess is at the compressor somewhere, because I saw a neon looking puddle under it once when the engine was out. but that could be anything!

Now, what are my odds that this is just a blown out o-ring?
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Low budget SAAB Viggen AC Reinstatement

Post by kevm14 »

I don't know, but the Ranger didn't appear to have a bad leak last time I vacuumed it and that charge lasted...less than 2 weeks? Maybe a test holding vacuum overnight would be better. Or rather than drive yourself crazy, replace O-rings and the parts you mentioned, vacuum it, charge it, and run it for a while. Nothing is a better indicator of leaks than a system that goes from working to kind of working to not working...and a pressure check that confirms a leak.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Low budget SAAB Viggen AC Reinstatement

Post by Fast_Ed »

Well, a lot has changed in the "over a year" since I last posted on this thread.

Interestingly, the car still held a charge when I put the gauges on it in the summer of 2016. AC had not worked for five years. So much for the "need to run the AC to keep the O-rings lubed" theory I guess. The compressor was not engaging, so I checked the relay in the under hood fuse box. After some 'staring at it,' I pulled out the multimeter and poked around. It turned out that there was no +12v going to the switched side of the relay. I then checked the fuse and found it blown. Replacing the fuse yielded cool air. The high side pressure was high, and the low side was a near vacuum. Strange, and when I think about it any normal car with a low side pressure cutoff switch (Roadmaster) would disengage the compressor at that point. So I did the stupid thing and added refrigerant. Vent temps got colder for a bit.. then the compressor cut out. Fuse was blown.

It was very hot that day (95F or so) so I went inside at that point and didn't touch it until 2017.
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Low budget SAAB Viggen AC Reinstatement

Post by Fast_Ed »

http://workshop-manuals.com/saab/9-3_vi ... sor_(620)/

Looks like the high pressure sensor also acts as the low pressure sensor, kicking in at 1.75 atmospheres (around 25 psi or 0.4V) and off at 24 ATM ( ~350psi or around 3.8V). And the interesting part is that I think I can test the system with a simple potentiometer hooked up to the three terminals, maybe with a DVM in there too. Use the +5V from the ecu and start the voltage at 0, increase to 0.4v and see if the compressor kicks in.

So running the system with no refrigerant would damage it immediately? The oil is still there probably.. I could put a small slug of 134 in there for testing I guess. Would be nice to hear the compressor run before I fill it all the way up..
Fast_Ed
Posts: 550
Joined: Wed Oct 23, 2013 9:45 pm

Re: Low budget SAAB Viggen AC Reinstatement

Post by Fast_Ed »

I found the connector for the AC compressor yesterday. You have to remove the PS Headlight to get to it. It is a single wire. Testing from the car side to the relay did not yield continuity.. There must be something between the two?

Testing the resistance of the clutch coil (compressor end of the plug to the neg battery terminal) showed about 1 ohm. I wiggled the wire everywhere on the compressor and between the compressor and connector. No change. I probably need a clutch. I found a GPD compressor for $102 on Rockauto. No clutches available there and the system is empty and under vacuum (firestone emptied it for me for $40). Easiest thing is probably replace the compressor.

I may still run 12V to the connector and see if it engages. I might even source it from the relay box so I blow the AC fuse again rather than making things really hot.

I read online that overly high pressures can stall the compressor and make the clutch slip. The heat from slipping can ruin the coil. Sounds like something that would have been pretty noisy and I would have heard it. but maybe not..
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