I was about to hook up a set of gauges and recharge my '93 940 Turbo and when I started to unscrew the cap on the high side port(which is on the compressor) it started to hiss and release Freon. Obviously, it doesn't have a Schraeder valve in that port. Is that normal? I have heard that on Volvos the high side isn't used so that would make sense, I guess.

 

That cap is really not enough to hold back the refrigerant pressure. They always have some sort of valve, however most likely leaking.

Top it off on the low side, however if going for an overhaul make sure you get a replacement valve specifically for AC systems

 

Was it a cap or an adapter that you were removing. The cap is not meant to hold the system pressure . You should be able to remove the caps of both the low and high pressure ports and hook up you gauges to verify and charge the system. The correct way to check and charge a system is by using both ports to charge the system. By the way if this is a 134A system the caps come off easy as the gauge hose assembly has quick connect fittings and not the old screw type used on R12 systems. Which one do you have.

 

Actually, it looks standard to have a cap and no valve. Check this out:


https://volvoforums.com/forum/volvo-...t-where-41838/

 

I have a 134a system and the cap on the compressor is a screw on cap so that tells me it's not a port designed for a quick connect fitting(which the low port near the drier does have) so it's not designed for checking the high side pressure. And like calredwood, in the link I gave, mine does not have a high side port near the condenser as the drawing shows it. I have run across comments on brickboard where some say Volvo's don't need the high side checked, hence no port. But that sure seems odd to me.


Check this out from a supposed Volvo mechanic:
http://www.justanswer.com/volvo/1e7w...volvo-960.html


and this:
http://forums.turbobricks.com/showthread.php?t=262447

 

Based on the above picture it looks like the fitting on the back of the compressor is the high pressure relief valve which blows off when the system goes over pressure. A safety valve. I would think that your high pressure line is located near or on the receiver/drier . There should be 2 capped valves there . 1 low pressure and 1 high pressure.

 

That's the problem, there is none. Every other car I've looked at has 2. Volvos do not - at least 240's, 740's and 940's. Where is it on yours?

 

UPDATE: My Chiltons manual says the high side port is on the back of the compressor, but why Volvo didn't put a Schraeder valve in there? Probably because they didn't intend it to be used for that. Maybe just for evacuating?

 

I've got an 89 740 and I have that pressure relief valve under the front near the condenser. I also have both high and low pressure connections on the rear of the compressor and another set on the receiver/drier.

 

Interesting

As I've seen it, if the cap is metal and attached to the compressor itself it is a pressure release port. All of the high pressure service valves I've seen have always been on the high pressure line near the compressor. I don't know if any changes were neasisary between the R12 and the 134A systems however. Did we determine what type of system this is, if it's been upgraded and the type of compressor?

For example mine is an R134A however it was upgraded from an R12 so it's got mostly new parts but the original compressor.

 

My system is an 134A from the factory. And, as I mentioned, Chilton says it is the high side service port. And like Calredwood you have to screw on an adapter to be able to use it for that purpose. I don't think the Volvo engineers forgot to put a Schrader valve in there by mistake. They obviously didn't know anything about A/C systems or they didn't see a need to use it.

 

Replacement compressors have both fittings right on the compressor suction & discharge line block - at least the ones at ACkits.com do anyway.

To do it right, you really need to see the high side pressure. That can tell you if you have condenser cooling issues, or an overcharge, plus it makes troubleshooting much easier.

I'm planning on overhauling my '93 940's system this summer. Was going to use the compressor out of my parts car, but I changed my mind and decided to go all new. Less problems that way. Any time you try and cut corners on A/C work, it will bite you in the bum sooner or later.

Here's the compressor I'll be using (for R12) - note the high & low side fittings: COMP TM-15HS EAR V ORG 2AG 135 3E 12V B 1W

Not much Volvo specific info on there, but the forum they have is the best if you want to learn about doing your own A/C work. Automotive AC Information Forum - ACKITS.COM

 

Good info. Thanks. I'll keep it for future reference. I got lucky, pumped in a couple of cans of r134 and it's colder than it's ever been - 37 degrees at 65 degrees ambient, idling. And 48 degrees at 80 degrees ambient, idling. Can't ask for more than that. If it ever leaks I'll put a valve on the high port cap and do a complete test.