My A/C keeps going through warm spells. So I bought a gauge, a can of oil and r134a. In the information packet that came with the guage it said for an outside temperature of 80F (which it was) the low pressure side should be 40-50 psi and the high pressure side should be 175-210 psi. I added one can (12 OZ) of 134a then checked the low pressure side it was 50 psi. Then I went to check the high pressure side but I couldn't for the life of me find the connector!!!! Does anyone know where the high pressure side connector is????!!!! The system seems to working fine now (short test drive, will know more tomorrow), but I'd like to see what the pressure is on the high side.
Also, is 50 psi at 80F to high for the low side? When I first checked the system it was between 20-25 psi for the low side, is adding one can (12 OZ) of 134a with out adding any oil OK???

Last question, the low pressure connector says 6Nm Max, what the heck is that in psi (if they convert correctly), I couldn't find the conversion.

Thanks in advance...

Scott K
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Scott K - 1994 850 Turbo 96K miles

there is no real high pressure side service port. there is a port on the back of the compressor i believe thsat will read the high side.

BUT your low side fitting will not fit the high side port, they are a different size to prevent the accidental hook up of a freon can to the high side, resutling in severe injury!

Like thre list said the best thing to do if you are not sure is to have the system completely evacuated and re charged.

i have charged my own and i have a very cold system. (had to replace the condensor, it had a leak)do it when it is real hot outside it will take a better charge nad give a better reading i have found.

Dan

Is 45 psi on the low side the correct low side pressure?
Also when I added the Freon I inverted the can. From what I now understand it seems like that was the wrong thing to do. The A/C is running fine right now, do I still run the risk of freezing the compressor?

Thanks in advance.

Scott K.
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Scott K - 1994 850 Turbo 99K miles

Scott,

There is no "correct" low-side pressure. It will vary. This is why people are advising that evacuating and refilling with a known, measured quantity of freon is the only way to put the system back into perfect spec.

Usually, freon should be added in gaseous form to prevent any liquid from reaching the compressor (since liquids don't compress, it won't like it!). This means leaving the can in a upright position. The only exceptions to this that I've read about are when you are adding an oil/freon mix. Read the directions carefully if this is the case.

If you already added freon in liquid form, and everything is working OK, you got away with it. Any liquid introduced to the system will very quickly assume the correct state (liquid or gas) in whatever side of the system it would normally be in.

Bottomline. If your assessment of the A/C system is that it's cooling fine, then it's time to declare victory (for the moment).

Gerald C

Thank you very much for you very informative responses. I think I will as you said declare victory for now and just enjoy the A/C. Although, I will keep my eye on it to see how bad of a leak I have. The evap lasted from 96 (last evap change) till now, so hopefully it's a REALLY small leak (which I'm sure it'll get bigger). To me there is no sense in adding dye because we all know (and cringe because we know) where it's leaking.

Thanks for all of the help

Scott

PS. I went through at least 2 (maybe three) evaporators from 94 to 96, this last one is my third (maybe fourth).
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Scott K - 1994 850 Turbo 99K miles

Unfortunately, Ron is right. The most correct procedure is to evacuate and recharge completely. And the odds are that the dye test will reveal a leak in the evaporator. And then the right thing to do is have that fixed. For >$1000.

Since this is the land of the free, however, you can choose to continue "tweaking" and "topping off" the freon amounts using low-pressure gauges, etc. This approach may not give you optimal cooling and will not make environmentalist friends, but it is your choice.

Gerald C

It's unlikely that you'll ever get the correct freon charge by using those POS tap-a-can devices so you'll likely be too high or too low and it'll still cool poorly either way.
The system only holds 1.65lbs and you've already added too much.
The best thing to do is to spend a few bucks and have it done right. Take the car to place with a recovery machine, have it recovered, evacuated and recharged with AC dye added so that when it loses its charge again, one can then see the dye with a blacklight. The machine also removes moisture during evacuation which is essential with 134a as moisture becomes acidic when it mixes with PAG oil.
As mentioned below, there is no high side fitting that you can tap into.

Scott

Pressure approx 40 to 45 psi dropping to approx 20-25 at the coolest.

50 is a tad high, you may have put a little too much in, keep an eye on it.

Oil stays in the system- you usually don't need to add any.

KP

if that is high, can it be lowered by depressing the schrader valve and letting a little out?

No. Free venting is illegal. And for a very good reason.

Have the refrigerant recoverd.

This is equivalent to dumping your used motor oil in the backyard.

Yes, you can do that. But you will be disqualified from receiving the Greenpeace merit badge. :)

Well after some research I found that the 850 doesn't have a high pressure service port. High pressure can only be read by a Volvo tool. I also read that you're supposed to add 134a by weight not by pressure. Does anyone know if 50 psi is any bit of an indication of how much 134a I have in the system? Or if I overcharged the system?

Thanks.

Scott K
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Scott K - 1994 850 Turbo 96K miles