Trying to fix my A/C, wondering what part to buy

[MrTruck805]

Hey All,

I'm trying to get the A/C running again in my 89 350 Jimmy. It wasn't running when I bought it, and the PO told me that a valve blew. I'm wondering if something is supposed to be hooked up to those red and blue caps? I can take more pictures easily if necessary.

I couldn't really tell what I'm missing from LMC Truck's catalog - http://www.lmctruck.com/icatalog/csb/full.aspx?Page=66

Thanks for any help.

 

[Big Ray]

STOP!!!


First off, you need to figure out what the issue is that's keeping it from working. You may just have a small pressure drop (leakage), just enough to keep it from working. Or you may need a complete system rebuild.

The caps are just that, caps. they cover the pressure ports that the gauges hook to (Blue-low pressure, red-high pressure)

You can easily mess up and wind up spending big $$ fixing it right.

I'm betting the compressor is shot...there's a great thread on rebuilding your a/c, let me find it & I'll link it.

edit: found it -->clickity

 

[Blue85]

Have you worked on A/C units before? If not, start with basic education on how they work.

There are really no valves in your system, except for the "relief valve" which vents refrigerant to prevent the system from grenading in an overpressure situation. That is only likely to happen if you have no airflow through the condendser while the compressor is running. It looks like somebody converted your system to r-134A. The factory R-12 caps were usually black and I've never seen a right-angle high side port on one before.

Please take pictures of the back of the compressor, the fan and clutch, the connections to the condenser and any stickers underhood talking about A/C. You are supposed to add a label when the system is converted.

To do any troubleshooting, you really need a gauge set.

 

[Fordum]

One of the biggest problems I have is translating problem descriptions when I start in on a project.
I agree that are not any of what you might call valves in an AC system, but he might have meant a valve in the compressor, or even a schrader valve which might explain the right angle add-on.

Either way, he is going to have to come up with some kind of gauge. If all the lines are attached, he can test for low gas by briefly jumpering across the low pressure switch on the accumulator to see if the compressor works. And if its knocking.

 

[Big Ray]

has it been converted to R134a...? The 90 leads me to think it has one of those cheap diy kits added to it.

Pull the caps off & see if it looks like there are adapters on the factory fittings...

edit: I see Blue 85 beat me to it!

 

[MrTruck805]

Thanks for the replies. The label still reads R-12. The label on the compressor reads "F/S:57237 Murray: 251103 Everco: A8548". Here are the pictures you guys asked for. Gauges were ordered the other day, and should be coming in the mail shortly.

Hopefully you guys can, see if the system appears to be all there from the pictures, and I can move forward with the diagnosis once I get the gauges.

Thanks for the help!

 

[MrTruck805]

Alright so I hooked up the AC Gauges, and they are both reading 0. The connectors ended up being r134a. I can see the compressor clutch spinning, but outside of that I guess I don't really know if the compressor is working.

I searched around the internet, and most people seemed to add a new charge of freon when both the high and low gauges were reading zero. I'm not sure if I should do that though, as you can't get r12 anymore, and even though the connectors were retrofitted to r134a, I don't know if anything else was, and as I understand it you aren't supposed to add r134a to an r12 system as it could damage the rubber seals.

Any ideas would be much appreciated.

 

[y5mgisi]

I would just top it off with "freeze 12". Google it or do a search here about it. Compatible with both r12 and r134 systems and cheap.

 

[British Slave]

Does the clutch engage? I would get a vacuum pump and see if the system is tight. Pull the vacuum and shut it in and watch the gauges. It should stay for 24 hours. If not, you have a leak. Usually you will see it drop pretty quick if there is a leak. Looking at your pics, I don't see an obvious leak, no oily spots. OR you can charge it with three cans and see what happens.

 

[Fordum]

If both gauges are reading 0, then its out of gas.

Brilliant statement huh?

Gas had to get out of it somehow. Look for oily places on all AC related parts. Hoses, fittings, whatever.
A system converted to 134A could use 12 with no problems other than the cost of the gas.
The compressor should not be turning with no pressure. The pulley should be, but the part in the middle should be sitting still.
With no pressure, more than likely air and moisture have gotten into the system.
So the drier will have to be changed,and a vacuum will have to pulled on the system to get the air out.
All that is a waste of time until you find the leak.

The correct way is to pressurize the system with some dry Nitrogen, spray all the lines and fittings with soap and look for bubbles.

But, this means buying the Nitrogen, which you will almost certainly never use again.
Next best, is to buy some cheap refrigerant, like the freeze stuff, and pump in enough to find the leak.

Once you find the leak, you will have to fix it, then replace the drier and orifice tube if yours uses one, pull a vacuum on the system for a while, then charge it up with your choice of gas.

If you have access to an electronic leak detector, you may have to charge it with 134A to find the leak, because some of the detectors will not work with the freeze type gases.

 

[MrTruck805]

Thanks for the replies. There really doesn't seem to be any kind of oil leak anywhere. If anything, the high pressure r134a adapter looked a little worse for the wear so I took it off to take a look at it. The green stuff started bubbling out when I did that. I put on a new adapter in place of the old one. The old adapter did seem to have some green corrosion around it. When I looked inside of it, there did seem to be a schrader valve in there which could be what the previous owner was talking about when he said a valve in the AC blew in regards to why it wasn't working.

Anyway, I guess I'll throw in a couple cans of freon and see what happens. If there was already r-12 to r-134a adapters on the high and low pressure ports, it's probably safe to assume the previous owner was putting in r-134a, even if there isn't any stickers under the hood indicating a conversion has taken place?

 

[y5mgisi]

Pretty safe bet. Most folks just go to the local parts store and buy one of those $34 conversion kits that come with the adapter fittings and a couple cans of the "special" r134.

 

[Big Ray]

check the hood insulation over the compressor...the comp. shaft seals are pretty much the first thing to go. it slings oil & freon as it's dying...

 

[Blue85]

It's rare for somebody to evacuate a working A/C system, so it the charge is gone, the odds are very good there is a leak. A can of refrigerant is a pretty good leak detector, but not the cheapest (or legal) process. You shoot some in and then (with the engine off) listen for leaks by ear and/or a stethoscope.

Nitrogen is the right tool, but to be honest I have used shop air plenty of times to find leaks. Leaks are very hard to find with a vacuum, since you easily get 4x the pressure differential with a little air/nitrogen (say 45psi). If you will be replacing the dryer (normal whenever there are major changes are has been a major leak) and will be vacuuming, the air is not the end of the world. It probably already has air in it already. Just try to minimize the amount of air you are flowing through the system and try to use a good drier. The more air that flows through, the more moisture the system can collect. You could also use CO2 or propane if you can rig up the right fitting adapters.

I like to shoot in a little refrigerant and engage the compressor, just to make sure the compressor works and there isn't a major blockage before putting a real charge in. At $16/12oz the cost of R134 isn't trivial to waste guessing at where a leak is. Plus it's technically illegal to charge unless you've verified the system. Troubleshoot. Don't guess.