2002 Silverado AC issue

1,314 Views | 24 Replies | Last: 5 yr ago by PetroAg87
PetroAg87
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AG
Ags,

My son's Silverado is only blowing hot air. It doesn't appear that the compressor is kicking on. I haven't checked pressure myself, but he says that he added refrigerant previously and it still wouldn't cycle on. I'm wondering if he might have a bad relay switch or low pressure switch? Hoping it is something like that instead of the compressor itself.

Is there a way to test those components? With the relay switch, I guess I can head down to the auto parts store and buy and try a new relay. But could I alternately use one of the other relays switches in the fuse box, or do these relays all have different ratings similar to fuse amperage? Or could I jump the relay switch by going from power pin to the compressor pin? With the low pressure switch, I have no clue how to test short of replacing with a new part. We may be getting to the point where it is time to take it to a pro, but I'm trying to rule out any easy fixes first.

Thanks Ags!
sts7049
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AG
when he says he "added refrigerant" does that mean he bought a can of magic a/c repair from the parts store? or did he get the system checked and filled properly?

PetroAg87
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AG
More the former. Bought a can of refrigerant from the auto parts store that included the pressure gauge and filled to correct range.

I may check with Autozone and see if they have manifold gauges that I can borrow to test out the pressure in the system. I've never done that before, but it doesn't seem too difficult as long as I follow the instructions...
Aggieangler93
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AG
I test the pressure switch in the following manner:

Turn off AC, turn off engine, and remove key. Pop out the electrical lead to the pressure switch located on the side of the accumulator (don't break the clips). Take a large paper clip, and bend it into a U. Insert the ends of the paperclip into the two female ports on the electrical lead. Start the truck, and turn on the AC.

If the AC works, you have a bad sensor. (note...in college...there was a box of paperclips in my glove box, just for this. I bet I went through 10 of those sensors. You can also use some duct tape to make the short more permanent if you need a few more miles in AC to get to the parts store for a new sensor!!!)

If not, you could have a bad sensor lead, or a myriad of other things. Since you are getting air coming out, I would not suspect the blower motor resistor, which is the other easy and obvious culprit IMHO. I have seen them go out often also, in Silverados.

Class of '93 - proud Dad of a '22 grad and a '26 student!
sts7049
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AG
those magic cans are garbage. you need to get proper gauges on the system and see what's going on.
PetroAg87
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AG
Thanks Aggieangler and sts. I'll check pressure charge and switch both and see if I one or the other is to blame. Appreciate the info.
1agswitchin4lanes
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AG
Where are you located?
PetroAg87
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AG
Houston
1agswitchin4lanes
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AG
You need to put gagues on it. If you're on the west side, you can bring it by the House.
PetroAg87
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AG
Thanks for the offer but we're down in Clear Lake. I am going to borrow some gauges from Autozone and check out the pressures though. Seems like a fairly basic test to run...
Silvy
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AG
In Galveston if you want to go South
PetroAg87
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AG
Appreciate it. I think the son and I will get the gauges from an auto supply store and give it a go. If the process provides harder than it seems, I may take you up on your offer!
PetroAg87
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AG
UPDATE: So we borrowed a manifold gauge system from Autozone and tested the system. Zero pressure on both low and high pressure sides (and yes I double checked to make sure valves were open).

So it would seem to be telling me that I have a leak somewhere in the system? Next step might be to put some refrigerant in, see if the compressor is working short term, and try and find the leak? Or maybe try and pull a vacuum on the system and see if that is possible (with a leak, I'm guessing that I won't be able to). Or I might be at the point of taking it in and letting the experts chase the leak.
mAgnoliAg
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AG
My 02 Silverado had constant ac issues ever since I had it. Great truck not too many problems but ac issues galore
Silvy
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AG
You should be able to pull a decent vacuum with a leak. If it doesn't pull any kind of vacuum, you have a large leak.

Run vacuum pump on system for 15 min and then turn off pump see how system holds vacuum over 15 min span. If it doesn't move much, if it all, I'd throw however much refrigerant in that the system takes.
PetroAg87
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AG
So latest update...

We pulled a vacuum on the system and waited. Apparently we do have a leak as it took about 30 minutes for the low pressure gauge to equalize back to atmospheric pressure.

Next step I suppose is to add a bottle of refrigerant that contains the UV dye and see if I can chase the leak. If so and it turns out to be a hose, o-ring, etc., than I'll try and repair. Any non easily replaceable item...in to the shop it goes. At least I know enough to give them some background and make sure that they know that I have done some diagnostics myself!
Silvy
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AG
Before putting dye in the system, have you looked around looking for relatively dirty spots where dirt/dust is sticking to the systems oil?
PetroAg87
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AG
I haven't, but I'll do that.
PetroAg87
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AG
UPDATE: So we pulled a vacuum on the system yesterday and then proceeded to add refrigerant. Good news is that gauges showed the system pressuring up, the compressor started kicking on, and we soon had very cold air blowing in the cab. So all parts seem to be functioning OK.

Bad news is that when I removed the coupling from the high pressure port, there was a detectable hiss/leak coming from that schrader valve. Nothing I could do to stop it, so I am sure that by this morning, my refrigerant has leaked off.

I've ordered a new Schrader valve ($6.00) online and will have to replace. I'm hoping that maybe that was the source of the original leak and replacement will be all that I have to do before recharging and getting the system back in working order. We'll see....
Silvy
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AG
I can't recall exactly, but is it the low pressure side that has the standard schrader valve and the high side is the valve w/o removable schrader?

If it's the high side, it takes a special socket to remove. My coworker ordered one for $20 or so.
PetroAg87
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AG
I didn't realize this until you mentioned it. Doing some research, it is indeed the high side that potentially requires the special socket. Looks like it runs around $20 or so by the time you factor in base cost and shipping.

Lots of people online are saying that you can use a 16mm or adjustable wrench as long as the valve gives you enough room to apply. Risk it appears is rounding off if you don't have a proper grip.
Silvy
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AG
I think the smart move is just buying the socket and not having to worry about it. An additional $20 is nothing to have the sumbish blowing 40 degrees out of the vents.
PetroAg87
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Yeah, hate to buy a one time use socket, but also don't want to tear the metal piping or new valve up by having to bite into it with a set of pliers or having a wrench that isn't tight enough. Cost me ~$12 and free shipping with Amazon Prime.
PetroAg87
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AG
New update: I went ahead and spent the $12 to get the special socket for the high pressure valve. Incredibly simple to remove the old valve and install the new one. I pulled a vacuum on the system and recharged with 12 ounces of refrigerant. That was enough to get the compressor spinning and confirm that cold air was blowing.

Still blowing cold air the next morning, so I have just let it sit for a couple of days to see if the original leak might have been in the high pressure port valve, or if I might still have a leak elsewhere. If it is still blowing cool, I'll put the gauges back on the system and finish charging the system with another 12 ounces of refrigerant.

One new question for the experts: It is appearing that all of the components of the system are still working fine, but obviously the system lost all of its refrigerant due to the leak. As I recharge the system, do I need to add AC oil to the system also? I've seen a can of refrigerant that contains 2 oz of ac oil and 1 oz of refrigerant that I could use to top of the system (takes 25.9 oz total). But I have also seen warnings about not adding AC oil if not needed. If all of the refrigerant leaked at some point, does that mean that the oil evacuated as well?
Silvy
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AG
You'll only lose oil from a very sudden leak or when larger components are replaced, you won't need to add oil.
PetroAg87
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Good. One less thing to worry about. Thanks for all of the assistance out here. Certainly saved me some coin, but also feels good knowing that I now have a much better understanding of these AC systems.
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