98 Suburban 2WD/5.7L AC Issue - HELP
 

Started off with less than 6 month old AC Delco compressor stopped engaging going down the road on Saturday. Of course now won't blow cold.

In testing the situation I jumped the rear compressor switch connector on the back the compressor to the battery and great news - the compressor engaged.

But now....my AC controller on the dash has no lights when I push activate the AC or Recirculate button and those buttons do nothing.
Plus I have lost control over where the air goes to.
I made a bad situation even worse.

AC relay is brand new. AC fuses in the door panel and under the hood all good.

Did I blow the controller?
Is there a fuse somewhere that works the AC controller?

Hot in Texas so I asking for help here.
Thanks in advance.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Does the blower motor still work? If so, then you have power to the switch panel. If nothing that the control panel controls works, then you have a power source issue, like a fuse or wiring issue.

Here is a link to schematics from a factory service manual for a 95, but they should be the same for a 98. https://flic.kr/s/aHsm77966y

Yes sir the blower motor still works
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Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Hey Mike
I can't find it on the schematic at all.

Does anyone else know what fuse provides power to the AC controller functions?

Thanks

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

There should be a 25A fuse in the block in the dash by the driver's side door.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Also, if the fuse under the hood (50A) is not working then I believe the A/C functions do not work.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I do know the 25 amp fuse in the door is good. The one small one labeled AC under the hood is good as well.

I will check the 50 amp fuse and report back.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

ALL 50 amp fuses are GOOD

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Ok, I'm still searching for another schematic, but in the meantime can you check the low side pressure port? The compressor will not engage if the low side pressure is too low.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Low side pressure port on drier is brand new. Just bought and tested it Saturday.
I have no way to test it again without controller functions.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

According to another schematic I found there is a 10A fuse for the low pressure switch.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I know you said the AC relay is brand new. It seems like it's the only common piece between the controller and the a/c system. can you test that as well just in case?

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

No but since it is brand new I can take that sucker back and get a brand new one.

I wonder what the relay has to do with the controller functions.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

The 10A fuse is in the underhood fuse box.

There is also a relay in the underhood fuse box.



When testing the A/C system, its never a good idea to use jumpers to get the compressor to work. It's better to check for voltage at connectors than it is to apply voltage to components. There are 2 pressure switches, and the PCM is also involved in the compressor clutch activation. You are probably low on refrigerant. It would be a better case scenario if your HVAC controls are fried. That would be better than having a fried driver in the PCM.


There is no need to start 2 threads for the same problem.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I have two separate issues so two different threads. If it takes 10 threads to get AC in Texas and faster help so be it.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I am not low on Freon. Levels are accurate with professional set of gauges. I tested the connector with methods that dozens of guys on here have recommended. Not one out of ten said to not do it.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Humor me...say someone was low on Freon would that make the controller AC and recirc lights not work when you push them or where to send air?

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

The air deflector should work regardless of the A/C condition, so you should be able to select front vents, defrost, or floor. The A/C light still should come on when low on freon (ask me how I know), but the compressor will not kick on. If the relay is bad, the A/C lights won't come on (to the best of my knowledge).

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Right. Thanks Mike.
I will change out the relay and then replace the controller if the relay doesn't fix it.

I have a feeling I shorted out the controller.

Thanks for all your help. I'll report back.

BTW I did swap the AC relay and the fuel pump relay and there was no change on the controller. I think I just flat smoked it - probably the circuit board in the rear.

Once I get the next controller in, I can go back to trying to figure why the compressor is not kicking on. If I am low on Freon, my gauges are not being truthful

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

The forum rules dictate the number of threads you should make, not the weather in texas. Your other thread will most likely get deleted or merged with this one. If it gets merged then the posts get funky and out of order.

The only way to know for sure if you have the correct amount of refrigerant is to evacuate and recharge with the correct amount, or to have a functioning system and watch the pressures, and slowly add to the low side until you get good numbers.

You can't tell the proper level by hooking up gauges to a non operating system.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

If you don't like my post in more than one place then have it deleted. You pointing it out has no relevance over me needing immediate help.
I appreciate your comments but seriously I don't need technicalities right now...I am trying to get to the bottom of this.

It is NOT low on Freon

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I am not trying to start a pissing match. This forum is a great place because of the knowledgeable people willing to help each other out.

When you joined the forum, you checked a little box that’s says you read and understand the rules.

You should read them all, but specifically read the first 2 sentences and read number 13.

http://67-72chevytrucks.com/vboard/a...t.php?f=34&a=9

If you are in that much of a hurry to get it fixed, go spend hundreds at a shop instead of asking for free advice. We are just sharing our knowledge to help you with your problem.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I replaced the controller and now I am back to the original problem of the compressor not engaging.
The very first original problem was the ac stopped blowing cold at idle.
The compressor low side is WAY HIGH in the readings.
The compressor is not locked up and will turn by hand.
Last Saturday just going down the road the compressor stopped engaging.
Blowing hot.
I’m back to my original issue and the symptoms except now Compressor not engaging with low pressure terribly high.

I’ve read that the condenser can cause the issue of not cooling at idle. Any thoughts?
I hate pulling the condenser and going through all that if that’s not it.
Do these symptoms sound like the condenser?

Thank you

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

I replaced the controller and now I am back to the original problem of the compressor not engaging.
The very first original problem was the ac stopped blowing cold at idle.
The compressor low side is WAY HIGH in the readings.
The compressor is not locked up and will turn by hand.
Last Saturday just going down the road the compressor stopped engaging.
Blowing hot.
I’m back to my original issue and the symptoms except now Compressor not engaging with low pressure terribly high.

I’ve read that the condenser can cause the issue of not cooling at idle. I was wondering about that.
I just hate taking out the condenser if this is not the problem.
Thanks to all for the help.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Sorry for some reason it loaded response twice from iPad.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Every GMT400 I've owned, after they went to the center mounted heater, has had electrical issues at the switch panel. The high speed heater switch has been melted at the harness connector, in almost every single one I've ever pulled out. I've pulled 20-25 at wrecking yards, all but 2 showed damage, neither worked in the 3rd or 4th position lol.

Traded a 95 k1500 burb for a 98 Grand Prix GTP, blew the trans then traded it for a 91 k2500 burb with a 6" lift....which is now a 91 Honda CR500 but I digress....The heater panel actually started smoking on the highway, ruined the controls, would have caught fire without attention. Most of them aren't a fire hazard, just don't work on the higher speeds, but it's startling how many of these trucks have visible damage around the high speed switch.

Not sure if its related to the switch based on what you've done, but one time I pulled a heater fuse in summer to fix the control panel in my 91 R3500. Took two weeks to figure out why the transmission was stuck in limp mode. Someone at GM didn't see any problem with powering the DRAC or whatever that thing is off a fuse that you might pull for a hundred reasons, and still need to drive down the road.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Good to hear you are back to the original issue. :)

If you haven't checked it already, check the orifice tube. If it's clogged, then you might experience the issue you have now. IIRC on these trucks it is up near the radiator on the passenger side, just inside the grill.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

But I don't have frost on the vents or dryer so I never considered the issue to be the O tube.

That would cause the low side to have some much pressure?

Just seems like I would have other issues right? tell-tell signs.

In the end I guess I gotta take it to someone. Hate doing it, but i think I've gone as far as I can.

I really appreciate all the help seriously.

I just wish there was a way to know for sure but it feels like the condenser is involved somewhere.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

If the orifice tube is open too much, you are putting too much freon through the system and will get the freeze up. If it's closed too much or clogged, you could see high pressure on the low side as the pressure can't be relieved due to the clog.

But yeah, it might be time to take it somewhere just to get it resolved, especially in that heat.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

If I open it up and see that it is clogged. What is that a tell-tell sign of? If it's metal, I am assuming that is my brand new compressor gone bad.

Just learning here.
Thanks

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Could be pieces from the old compressor, since you had it replaced.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

The orifice tube is located at the junction in the A/C line on the passenger side inner fender. It is directly below the air cleaner.

The junction has aluminum threads on one side, and steel on the other. Sometimes threads get damaged and then youll have to buy new lines. The orifice tube can really be stuck in there too. A small needle nose pliers will work, but sometimes they are so stuck they break. Note the orientation upon removal. You don't want to install the new one backwards.

Was the new compressor installed by a shop? Most shops require replacing the dryer, the orifice tube, and flush the lines to get the warranty on the compressor.

Do you have rear a/c, and did it previously work too?

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

No the rear AC is not blowing cold either. Same as front. But it did work like front until AC compressor stopped engaging last Saturday.

Yes I replaced the compressor, dryer and o tube when I installed new compressor. I vac'd it down and did refill.

When I hook up test light to battery positive and touch compressor wire harness from back of compressor - the AC clutch will engage and I get cold air.

AC Relay is brand new. All fuses good.

Can a bad condenser cause this? I only ask this question because I go back to my original problem that was it not blowing cold at stop lights - idle.
Can the condenser completely fail and cause compressor not to engage?

I can't shoot dye into system to look for leak because AC won't engage.

Should I VAC it all the way down, and start from scratch? I guess I could take everything apart and look at the o tube.

Just not sure what the smartest approach would be money wise.

I do know the condenser has got some miles on it for sure. I would go ahead and replace the condenser if I knew a failed unit could cause the AC compressor to not come on.

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Low pressure side 95 psi (2:30 o'clock)
High pressure side 100 psi (8:30 o clock)

Reading on gauges

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

is that compressor running or compressor not running those look like normal static pressures when compressor is not engaged

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

have you checked the low pressure switch at the a/c drier these go bad alot and ive replaced alot it is a 2 wire switch i normally jump with a paper clip if i jump and compressor comes on pressure switch is bad it just screws off and has a valve that willc lose when screwed off so u dont lose and feron

When jumped compressor still don’t come on.
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Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

Increased pressure readings is usually due to a blocked orifice tube. when you replaced the compressor 6 months or so ago, did you check the orifice tube?

Re: 98 Suburban 2WD/5.7L AC Issue - HELP
 

read post #33

O tube replaced then. Brand new one now as well.
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