AC Doesn't Blow Cold Air

[mubai]

OK, here's another issue with my AC. It will blow cold for maybe a few minutes when you first drive then it's not as cold any more. I've changed the AC Pressure Cycling Switch back in Sept 2014, and it's been working fine. Do you think I should get a can refrigerant and add that? I would need to get the one with the gauge so I don't overfill it.

Truck is pushing 14 year and 217K miles.

 

[djthumper]

Definitely check your refrigerant. Top it off and then keep an eye on it to see if it is leaking down. I normally check mine in the spring to make sure it didn't get damaged when it wasn't used as much.

 

[mubai]

Off to PepBoys...

 

[MAY03LT]

Is the compressor cycling on/off in short intervals?

 

[mubai]

Ok, got a can of EZ Chill, I checked the pressure and it said about 120 psi. This was in the red section of the gauge. Red = "May have mechanical problems". I tested it a few times (removal and install). Didn't add any refrigerant.

I have been in the car for 15 minutes no short cycles and the air is ice cold.

I'm not sure where to go from here. I think Ill just leave it until it happens again.

 

[mubai]

Ugh! So annoying, after I posted that, I drove home and got the SES/REP lights P1271. I'll repost in my other thread. Also, the AC went warm, I imagine it's b/c of the SES/REP. I cleared the code and all was normal. Didn't feel like driving in limp mode back home.

 

[1ryanb]

MAY03LT -- I have the compressor cycling in short intervals and not blowing particularly cold. What does that usually mean?

The compressor has also started to while a little bit between 2000-2500 rpm. Not sure if this is a symptom or part of the problem. I have a feeling it is just the pulley though.

 

[c good]

You also have a high pressure cut out switch. If it's reading 120 on the low side it's way over charged and it cutting power to the compressor so it doesn't blow it up. Also, the whine you are hearing from the compressor is probably associated with the over charge. Over charge is just as bad as undercharge as far as cooling goes. There is a specific range of pressures on high and low sides so that it cools correctly. Over or under charge both result in no cooling. More is not better.

You really need to get a set of gauges on it to check both high and low side pressures to avoid damaging the system and before we can give you any definitive information These pressures need to be read with the compressor engaged and running. Average normal low side pressure ranges from 30-45 PSI. I don't remember high side pressures exactly but they are In the 170-200 range IIRC.

HTH c good

 

[mubai]

c good, Fail on my part for not reading my Haynes manual. You're right the car should have been on with the AC on. Anyway, here are pics of before and after the fill.

Prefill reading: 38 PSI


Postfill Reading - 39 PSI (I emptied the whole can.)


After running the truck about 10 minutes around town and bit on on the highway. The actual temps from the face vents were the following from Left to Right: 44F, 43F, 42F, 45F.

Seems like it's running fine for now.

Thanks again.

 

[c good]

That looks a lot better. Glad you're "chillin" once again.

 

[mubai]

OK, back to this again. AC doesn't blow cold air, just ambient warm air (in my case in Philly with 93F, really freakin' hot air). The compressor is not cold, no moisture around it and I don't hear it turning on. I'm not sure how to diagnose the issue here. If anyone can help with the steps I would appreciate it.

 

[Mounce]

Has it lost its charge? I know you added refrigerant and it worked so maybe it's got a leak?

 

[mubai]

Just drove out a few miles made some short stops. On the way there it was working again. On the way back it stopped working. I could tell the compressor wasn't kicking on. I dont think there is a leak, I think it has to do with the compressor not running. Well sometimes it does and most times it doesn't.

 

[meerschm]

Sometimes the clutch coil gets old and weak.

you know how to look at it and see if the clutch is engaged or not?



sometimes they just quit when it is hot.

(and you want it to work the most)

 

[meerschm]

the clutch has some thin washers that act as shims. some folks have been able to remove one or more and have it work.

you would have to remove the belt, and take out the bolt that holds the clutch plate on. then in some cases removing one of the washers lets it stay closer and the weak magnet from the coil then can pull it in to engage.

 

[mubai]

Thanks! I've never done this, so I'll have to see if it's in the Haynes manual.

 

[mubai]

Just watched a YouTube on AC Compressor Clutches...doesn't seem too bad. I now understand the shims/washers you were talking about. Would be nice if I could just find the clutch and just replace that.

 

[mubai]

OK, now I will have to wait until the AC cuts out to see if the clutch is not engaging. Now if I understand everything correctly, removing a washer/shim brings the clutch disk closer to the flywheel, which should allow it to engage.

 

[meerschm]

You can also check the gap with a couple index cards or such (or feeler gauges if you have a set)

You don't want it too close.

I posted a note on where I got a clutch. should be able to search and find it.

http://gmtnation.com/forums/topic/7652-ac-clutch-replacement/

might be of interest.

hope you get it figured out and fixed before it cools off.

 

[mubai]

Great! Thanks, found it here: http://gmtnation.com/forums/topic/13510-2002-trailblazer-ac-clutch/?p=436778

Ahh, stupid fan shroud. I hate that thing...and now I have to remove it.

 

[Mooseman]

If you cut a notch on the top of the shroud to clear the radiator neck for the top hose. it helps a lot.

 

[littleblazer]

If you catch it next time, like it running then cutting out, pull the plug off the low side cycling switch, the one on the metal can thing that's name always eludes me. Then jump it with a piece of wire and see if it comes back on. It sounds like the coil to me like everyone else said, or maybe a week relay even. I don't know, but it won't hurt to try that since it takes all of like 10 seconds. [emoji106]

 

[mubai]

How do you jump it? Are there only two pins?

 

[littleblazer]

How do you jump it? Are there only two pins?

Yep, just a two pin plug.

 

[Mooseman]

FYI, It's called a receiver/dryer. it could be a flaky low pressure switch. That test should confirm it.

 

[mubai]

Just to be clear, how do I jump it. I assume 12v from the battery. Does it matter which wires go which pins?

 

[littleblazer]

Just to be clear, how do I jump it. I assume 12v from the battery. Does it matter which wires go which pins?

No no. Just complete the circuit between the two. Wire in one pin running to the other is all. [emoji106]

 

[Mounce]

Wire goes from one pin of the harness straight to the other. Just bridging the gap.

Swooped by LB

 

[mubai]

Ahh thanks. Now I wont blow up the car. I love having a 14 year old truck with 214k miles on it that's supported by a great group of guys/gals, I learn so many things!

 

[mubai]

OK, I the issue didn't happen but I jumped the harness and the compressor did run and the clutch did engage, so that eliminates any wire harness issue.

Now having a clear understanding how the clutch works, with the truck off, I decided to tap the clutch with wrench in case there was any debris that blocking it from engaging. I then sprayed the gap with PB blaster and let it sit overnight. It's been working fine, since then. I decided to clean the condenser today, sprayed some cleaner on it, hosed it down, then used a shop vac with bristle brush to suck up any dirt, bugs and water.



meerschmhttp://gmtnation.com/forums/user/8039-meerschm/ - i think you were spot on with the clutch issue. Thanks!