A/C System diagnosis

[HSKR]

So the A/C in my Spirit R/T sucks. I just replaced a leaking seal on condensor(there was still some pressure on the system before I changed it) and put a vaccum on system. Kept vacuum on for 45 minutes, then let it sit and it held that vacuum for 15 minutes. Charged it back up.

Low side reads 30psi with compressor engaged and A/C on high
High side reads 260psi.

All the charts I find the high side should be closer to 200 and the low side should be around 40. Reading he pressure charts and online diagnosis flow charts, it says with a "normal" low side and high, high side, means there is air in the system. This is not the case.

[turbovanman²]

Is the fan coming on? I would check or replace the valve assembly, can't remember the name, at the firewall if you're 100% sure the compressor is good. How do the lines feel temp wise coming off the compressor?

[A.J.]

Are you using R12 or R134a?

[HSKR]

R134A. Lines of compressor, low side(larger line) going to firewall is cold, other one coming from condenser is warm. Was wondering if maybe the expansion valve was bad, but online is says if both sides are high then check expansion valve. Don't want to waste anymore refrigerant than I need to to make it right.

[A.J.]

How much R134a are you putting in? The R12 charge is 2 lbs so with the formula I have for conversions, your R134a charge should be 1.55 lbs.

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What's the ambient air temperature there? The tube and fin condensers that these cars came with suck when converting to R134a, at least in AZ. A parallel flow condenser is ideal.

[HSKR]

Started with 24oz, and the low side was still a little low so added another 8oz. Which got me to 30psi on low side. Ambient temp at the time was 75 degrees.

[ajakeski]

Did you change the expansion valve? How about the accumulator?
If either are old and full of crud, system pressure will be effected.
Another issue could be the valves in the compressor. A stuck or bad valve will cause irregular pressure.
If AC system sealer had been added to the system in the past due to leaks, any component could be bad. Sealer is a band aid repair and usually causes more problems han it fixes.
Most AC shops won't touch a car that has had sealer added to the AC system because of the contamination risk it presents to air conditioning equipment.

You may be looking at replacing several parts of the AC system to get it workiing correctly. These can become a can of worms really quickly.

[HSKR]

Have not replaced expansion valve. Accumulator/dryer has been replaced as well as the compressor. I didn't add any sealer by itslef, but the refridgerant charge cans I bought from Walmart came with sealer in them. Now that I am in Nebraska I have more options than when I ws in Cali.

[wheming]

Another simple thing to check is to simply make sure the outside of your condenser is clean. You will actually need to use some coil cleaner to clean it. Just hosing off with water won't really clean it. But, hosing water on it while the a/c is running will tell you that the condenser is dirty (if the head pressure returns to normal.)

But, i'll echo the others and say you might have bigger problems. Just try the simple ones first. Any time you open a system up it is a good idea to replace the dryer. And 91 was originally R12 wasn't it? So someone did the conversion and who knows if they did it properly.

[HSKR]

I did the conversion on it. It worked better before but it had a leak. Fixed the leak and now this.

[turbovanman²]

Did you vacuum the system or just fill it up? If you filled it up, that won't work. Correct charge with 134A is what A.J said, or 25 oz's.

[going4speed]

Did you replace the pressure switch with an R134 compatible switch? I think that makes a difference. I just redid the AC from r12 to r134 in the lancer. The radiator shroud says 38oz of R12 and the mechanic said it took just shy of 30 ounces to meet the gauges to what he expected to see. I replaced compressor, dryer, pressure switch, expansion valve, all gaskets in the whole system then had it charged. It acts a tad funny when you first fire it up as the compressor clicks on and off rather quick for the first few minutes. After that it clicks at a normal cycle and cools the car off great.

[turbovanman²]

I never replaced the any switch's or valves on the van, blew ice cold.

[85boostbox]

Is the fan coming on??? Does it get colder going down the road, or when you rev and hold rpms around 1500?

[HSKR]

Yes I put a vacuum on it, mentioned that in my first post. Fan comes on, doesn't blow any colder driving down road. Will replace expansion valve and go from there. Its only $20 for a new one.

[wheming]

Do yourself a favor and put a new dryer.
I'd leave the vacuum pump on longer to make sure you get any moisture out.

[HSKR]

Dryer has bee. Replaced and system has not sat open since. If 45 minutes with a vacuum on isn't enough then there are more serious issues. Meaning it probably won't hold vacuum.

[going4speed]

The lower port on my expansion valve was almost plugged with something. Did not really dig into it but could not find that residue anywhere else in the system.

[wheming]

Sure.
But there's more to it than just checking for a leak.
Putting under a vacuum will remove any moisture and non-condensible gas. Moisture takes a longer time to remove (with vacuum) than a simple vac leak check.
A new dryer is a good idea, and its good you did it recently then. But unless you know how that part was stored, it still could have been absorbing moisture (if it wasn't properly sealed).
I've always kept vacuum on it longer. One car, which had a/c lines open for a couple years before i got the car, i kept vacuum on it more than 24 hrs. I didn't even change the dryer in that car and when i charged it up (by weight) it was perfect and cool. 3 years later it was still perfect.
(And yes i am aware that i didn't follow then the advice i gave you now.)
I just thought it might help. I hope you get it working. I know here in the south, it is a necessity.

[HSKR]

This isnt the first time its had vacuum on it for that long. I k ow vacuum removes moisture, which is why I kept it on it for so long.