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Old 05-13-2024, 03:18 PM
Scratch Scratch is offline
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Default Car AC advice

We bought a 2005 suburban and the ac doesn’t work. The previous owner said there was a slow leak and he just bought one of those auto parts store cans with the built in gauges every summer and it worked… I had my doubts.

I’m no stranger to auto repair, Im in the middle of my 4th body off frame restoration right now. I’ve replaced a dozen or so engines in my 50 years, and have replaced an ac clutch before too.

He did have a brand new can of refrigerant in the back so I hooked it up. It said it did not need any refrigerant and was full. Then I noticed the ac clutch wasn’t spinning with the compressor pulley.

The belt was spinning the ac pulley, but not the clutch with it. I checked the fuse… good. I found but did not check the relay, (not sure how to check it) Then I pulled the 2 wire connector going to the clutch. I hooked up a positive and negative wire to the connector completely bypassing the wiring harness, and I could hear and see the clutch engage.

I started the car, turned on the AC on the dash, put it in recirculate mode, and connected my two wires again, the clutch started spinning like normal, but I am not getting cool air from the vents.

I’m pretty sure the seller was lying about the leak as the gauge did say it was full. I know something’s wonky with the electrical, maybe it’s the relay, but shouldn’t I be able to bypass the harness, get the clutch to spin the compressor and move that refrigerant to get cold air out of the vents? I guess the compressor could be bad too but I’m not sure how to test that. I don’t mind replacing the compressor but I was just really hoping to not have to bring it in to recycle the refrigerant.

Any ideas?
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  #2  
Old 05-13-2024, 04:29 PM
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Whitetrash Whitetrash is offline
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A lot of the time you can swap out the relay you want to check with another for something else on your rig to do a quick test
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Old 05-13-2024, 05:51 PM
slip knot slip knot is offline
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I'm going to say its low on gas. if you bypass the compressor and its not getting cool you dont have a relay problem you have a refrigerant problem. if the gas charge is low the compressor will lock itself out and wont run. hook up a real gauge to the test ports and see what kind of numbers you see.
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Old 05-13-2024, 06:09 PM
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I suggest you down load the manual for your filler gauge.

Not being specific with a 2005 suburban.
in general the gauge measures the suction side when the pump is running, otherwise the lines equalize.

In general if the system gets too low the pump will not start, low pressure switch prevents pump from getting power.

Is hard to know how much to add, do not over charge a system on my car I over charged it and screwed it up.
If in doubt under charge it.
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Old 05-13-2024, 07:55 PM
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It was a ford but I had a 2006 truck that would blow somewhat cold air until you had driven it a bit and then it wasn't cooling at all. I tried charging it with a can with a gauge and no matter how much I put in it, the pressure was not climbing as the directions indicated it should. I drove it some more and it started puking refrigerant at random and still wan't consistently cooling.

I gave up and took it to a dealer. They ran some diagnostics and came back and told me there was an internal relay on the PCM that was failing. All the mechanical parts and basic relays and wiring I could check were fine but an internal part to the computer was bad and was not calling for the compressor to run or something.

1100 bucks for a new PCM and I was good to go with cold AC again. Hated to do that but figured if the PCM was losing parts I'd eventually be stranded anyhow.
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Old 05-14-2024, 01:19 AM
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Sounds like a blend door is not functioning on top of your other problems. If the blend door won't open to the correct position, your cold air is going somewhere else, maybe the windshield defrost? What's the temp up there? Are the defrost and all the other ports working like they should?
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Old 05-14-2024, 09:19 AM
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I loathe working on a/c systems in cars. Just never had much luck repairing or replacing them. The primary reason is that I've never wanted to invest in the money or tools to do the job properly. Had I done that the very first time one of my cars had a problem I'd likely be very much ahead of all the money I've blown on those stupid refill cans.

Usually those cans will work easily if that's the true and only problem. It wouldn't have needed the refill if it wasn't leaking though, so you're always starting with more than one issue.

My vote would be to take it to a shop and have them figure it out and fix it. It likely won't be cheap but you'll end up money ahead.
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Old 05-14-2024, 11:19 AM
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Some cars have a compressor control valve. Those can get lazy and not allow full refrigerant flow.

A set of AC gauges is a worthwhile investment. I wouldn't think of servicing a system without first looking at gauge readings before and after. They also provide a way to add refrigerant or draw a vacuum to boil off moisture.

When first connecting the gauges, if they barely show a reading on the scale you have a leak which needs to be fixed before you go further. To find the leak you need a leak detector. Yet another investment.

With the car running and AC on, if low side pressure is good but high side is low that is a reliable sign that you need refrigerant. If both are the same pressure, that tells you the compressor is not working and/or a bad orifice/TXV. If the high side is TOO high, it could indicate overcharged and/or poor airflow over the condensor as in fans are not working or condensor is clogged. It is overall a bit more complicated than that...
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  #9  
Old 05-14-2024, 12:03 PM
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Quote:
Originally Posted by Matt Shade View Post
It was a ford but I had a 2006 truck that would blow somewhat cold air until you had driven it a bit and then it wasn't cooling at all. I tried charging it with a can with a gauge and no matter how much I put in it, the pressure was not climbing as the directions indicated it should. I drove it some more and it started puking refrigerant at random and still wan't consistently cooling.

I gave up and took it to a dealer. They ran some diagnostics and came back and told me there was an internal relay on the PCM that was failing. All the mechanical parts and basic relays and wiring I could check were fine but an internal part to the computer was bad and was not calling for the compressor to run or something.

1100 bucks for a new PCM and I was good to go with cold AC again. Hated to do that but figured if the PCM was losing parts I'd eventually be stranded anyhow.
Last time my compressor took a shit on my 2011 Exploder, it was $1100, took it to good mech. he found another leak as well, sorted all the problems.

Was worth it.
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Old 05-14-2024, 07:44 PM
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Quote:
Originally Posted by Shade Tree Welder View Post
Last time my compressor took a shit on my 2011 Exploder, it was $1100, took it to good mech. he found another leak as well, sorted all the problems.

Was worth it.
Yeah, I honestly would have spent that even if I wasn't worried about the PCM shitting the bed. I'm all about windows down on backroads at 40 mph but on a 7 hour road trip towing a trailer 70mph I want my AC!
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