BJ74 AC Issues- advice? (1 Viewer)

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I'm not an AC expert. If it was a standard over the counter AC compressor I'd probably just take it to a shop, but for now I'm trying to figure out what's up with my AC before I just start blindly throwing parts at it or take it in. My AC on my BJ74 was non-op when I got it but everything seemed to work. I had a buddy of mine convert it to R134 and it worked alright, like converted ACs tend to do. I didn't use the AC for months over the winter, fired it up for the first time this summer and at first it was weak, then non existent. It appears the clutch is engaging and the idle up is still happening, so I'm trying to figure out what my next step should be before I either just wrenching or take it to an AC place. The nose of the compressor is a bit greasy but it's an old truck and it kinda matches the general theme of everything else under the hood that hasn't been replaced. All of the connections in the system are dry.

Should I-
A. Throw some stop leak and jam a can of coolant into it and see what happens?
B. Assume I have a bad compressor and proceed with just replacing the compressor?
C. Just take it to an AC shop and have them diagnose

Thank you
 

jblueridge

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I took mine to an AC shop. I gave them a new compressor and they swapped the 24V clutch.
They insisted on filling it with real Freon (R12?) since that is what it was designed to use.
I was told the trick is to make sure to use the ac at least once/week all year round to keep o-rings lubed and tight.
 

loeky

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Check if you can see bubbles in the viewport at the front of the truck with the AC on as a first data point. That'll confirm the AC idle up is happening due to enough pressure [it won't idle and no clutch if absolutely empty] with /something/ in the system, even if it's low. Then throw a new can of R134 into it from the autoparts store to top it off.

If it holds and blows cold, yay. If it doesn't - you've got a leak somewhere that you'll need to figure out [o rings, or real leak via hardlines or at the high pressure lines] with dye or via a reputable shop.

Mine required new high pressure hoses - something I couldn't have done myself, and wasn't cheap but worth it to have AC in the summer.
 

Honger

Joel, TLCA #21509
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You really need a gauge set to be able to diagnose things. Is the pressure low, reflective of a leak? Low pressure can allow the system to still work but cool poorly. Also, a blown compressor can still cycle but not generate the pressure needed to cool.

Oily residue on the nose of the compressor isn't good... unless you know it came from somewhere else. If your leak is from the compressor you're either doing a rebuild or replacement.

I'd say get a gauge set on, check your pressure. If you're low, inject the dye and then drive it with AC a few times and then check for your leak with a blacklight. If your pressure is fine, then you've likely got a compressor that's no long generating pressure OR a bad expansion valve. Did you replace the expansion valve when you converted? How about the drier bottle?
 
Joined
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Los Angeles
Check if you can see bubbles in the viewport at the front of the truck with the AC on as a first data point. That'll confirm the AC idle up is happening due to enough pressure [it won't idle and no clutch if absolutely empty] with /something/ in the system, even if it's low. Then throw a new can of R134 into it from the autoparts store to top it off.

If it holds and blows cold, yay. If it doesn't - you've got a leak somewhere that you'll need to figure out [o rings, or real leak via hardlines or at the high pressure lines] with dye or via a reputable shop.

Mine required new high pressure hoses - something I couldn't have done myself, and wasn't cheap but worth it to have AC in the summer.

I didn't bother to check the view port since the clutch is indeed firing, which means that there's still enough to trip the pressure switch. Thinking I may try and jam a bottle of R134 into it with stop leak and see what happens since it clearly has held onto something...
 

loeky

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Reco waiting on the stop leak. It's good, but if you really just need a top up w/ a very slow leak ... it'll gum up the system for no reason. Fill it up and assess from there if you want to toss in the glue, or troubleshoot for a 'real' fix.

Some of the 134 cans come with dye, I think... You could/should go ahead with that as a simple first check and start looking for leaks with a blacklight. That won't gum it up.
 
Joined
May 22, 2014
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Los Angeles
You really need a gauge set to be able to diagnose things. Is the pressure low, reflective of a leak? Low pressure can allow the system to still work but cool poorly. Also, a blown compressor can still cycle but not generate the pressure needed to cool.

Oily residue on the nose of the compressor isn't good... unless you know it came from somewhere else. If your leak is from the compressor you're either doing a rebuild or replacement.

I'd say get a gauge set on, check your pressure. If you're low, inject the dye and then drive it with AC a few times and then check for your leak with a blacklight. If your pressure is fine, then you've likely got a compressor that's no long generating pressure OR a bad expansion valve. Did you replace the expansion valve when you converted? How about the drier bottle?

Yeah, no gauge. It was holding pressure before, it worked all last summer. I can't figure out what the residue is from. It looks like it's been there a while but it's tough to say. Didn't replace any other components. I went over the system and after we filled it it ran fine and I didn't think much of it, it held pressure and seemed great. Any other time I've had bad AC in a vehicle I've always been able to chase it down, but everything else looks nice and dry and tidy.
 
Joined
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Reco waiting on the stop leak. It's good, but if you really just need a top up w/ a very slow leak ... it'll gum up the system for no reason. Fill it up and assess from there if you want to toss in the glue, or troubleshoot for a 'real' fix.

Some of the 134 cans come with dye, I think... You could/should go ahead with that as a simple first check and start looking for leaks with a blacklight. That won't gum it up.

I hadn't thought of that. I'll have to look, that seems like a good start.
 

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