It's been a long time since I've posted here. My wife is having an issue with her TB's air conditioner, so here I am again. In the past month the A/C in the Trailblazer(2004 LT w/4.3 I6)will just stop blowing cold as if the compressor has stopped. The air is cool and humid. Then, usually within a minute or so, it is working as it should. Occasionally it will stay off for several minutes but it always recovers. My wife drives it all the time so I have not had the chance to stop and see if the compressor is actually engaging or not. The few times I have been in the TB and it happened we were on the interstate so I didn't get a chance to stop before it started working again. She says it happens almost daily and sometimes on the highway, sometimes in town. Any ideas? It has the digital A/C and other than this it has been an awesome, trouble free vehicle, with the odometer just rolling over 151 thousand miles.
A/C shuts off at random
- Thread starter Badbart
- Start date
gmcman
Member
- Dec 12, 2011
- 4,673
I would do what I just did and you need this to diagnose.....but if you have a Harbor Freight near you, go pick up a set of gauges for about $55. Part number 60806.
http://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html
Could be low pressure switch. Take a paper clip and remove harness and momentarily jump the leads, if it turns on then that's your issue. Other than that, we will need pressure readings to diagnose either a failing coil or high pressure switch or even proper charge.
http://www.harborfreight.com/ac-r134a-manifold-gauge-set-60806.html
Could be low pressure switch. Take a paper clip and remove harness and momentarily jump the leads, if it turns on then that's your issue. Other than that, we will need pressure readings to diagnose either a failing coil or high pressure switch or even proper charge.
Mooseman
Moderator
Because it is happening at speed, I would also be inclined at looking at the compressor clutch. As it spins faster, it would be harder for it to hold and would slip. Check the gap and if necessary, remove a shim or two to close the gap. I don't know what it should be but it should be very minimal, just enough so it doesn't rub while disengaged.
BanditGTP
Member
Hey guys. I didn't want to start another thread about the same subject that BADBART just started. Let me know if I'm out of place and should start my own thread. I definitely don't want to hijack his.
I'm having the same problem as BADBART and I'm not sure if his trouble is happening only on the highway or if it's just harder to diagnose while zipping along at 60mph. I've noticed mine happening at all times and all speeds. I haven't noticed it happen during the first 8-10 minutes of starting the truck when cold. I've tried the paperclip trick and had no luck with that and I also swapped out the a/c relay with another relay and also had no luck. One question I have is when I was swapping the relay, I tried approx 15 times to insert and then remove the relay. Every time I inserted the relay, the compressor clutch engaged. I've heard that sometimes it may be the compressor clutch but since it engaged every time, do you think it would be safe to say the clutch is ok?
Moose on the loose....How would you go about removing a shim?
Thanks
I'm having the same problem as BADBART and I'm not sure if his trouble is happening only on the highway or if it's just harder to diagnose while zipping along at 60mph. I've noticed mine happening at all times and all speeds. I haven't noticed it happen during the first 8-10 minutes of starting the truck when cold. I've tried the paperclip trick and had no luck with that and I also swapped out the a/c relay with another relay and also had no luck. One question I have is when I was swapping the relay, I tried approx 15 times to insert and then remove the relay. Every time I inserted the relay, the compressor clutch engaged. I've heard that sometimes it may be the compressor clutch but since it engaged every time, do you think it would be safe to say the clutch is ok?
Moose on the loose....How would you go about removing a shim?
Thanks
Mooseman
Moderator
Mooseman
Moderator
Cycling is normal if RPM is higher than idle, not normal if at idle unless it's really cool outside..
BanditGTP
Member
When the compressor is off, it is usually off for as little as 5 minutes but also as much as 10 to 15 minutes. I'm not sure that would be considered cycling.
I forgot to mention. The first time I noticed this problem it was probably in the low 70's but now it's in the 80's and 90's.
I forgot to mention. The first time I noticed this problem it was probably in the low 70's but now it's in the 80's and 90's.
BanditGTP
Member
I'll have to go out and pick up a set. Probably won't get to it until next week. Would trying the paperclip jumper bypass the low freon if it is indeed low and cause the compressor to kick in?
Mooseman
Moderator
BanditGTP
Member
I wouldn't plan to use the paperclip as a bypass to the sensor and therefore force the compressor to stay engaged. I was just using it to test if the sensor was causing the compressor to shut off. Since the paperclip test didn't work, would that also mean I wouldn't need to get a test gauge because it seems like the problem is being caused by something other than the possible lack of freon?
Last year I had the same issue with my wife's Envoy. It the summer, the A/C would sometimes stop working (sometimes after 15 minutes and sometimes after an hour of interstate travel). I replaced the low pressure switch and relay and still no luck. I got gauges from HF and filled the system to the proper level and still no luck. Finally, I took it to a shop and they vacummed filled it. Knock on wood, but it's worked ever since.
Mooseman
Moderator
Tiggerr
Member
Mooseman said:
+1 Very good thought at that... Was thinking along those lines too. Wouldn't take much moisture for that to happen. A little air in the system probably wouldn't be helpful either.
gmcman
Member
- Dec 12, 2011
- 4,673
Watch your clutch engage when the motor is cold, have either someone turn the AC on or pull the relay and do it yourself. Does it engage firmly? Then when it's hot and acting up, check the clutch engagement again, this time with the engine off but key on obviously. Watch the clutch and does it click and engage firmly or just kinda slowly move but not fully engage?
I drove it today in 97* heat for about 50-60 miles in town and highway. It worked as good as a new one, never wavered, quite frosty. We'll see what tomorrow brings.
It acted up last Thursday again while we were in town on a hot day. The compressor shut off and never re-engaged. I called the garage I take the rest of my fleet to and he told me to bring it on in. They found a leaking shrader valve and did an evac and added about a half a pound of Freon and a shot of oil, problem solved! Nice and frosty again. I was surprised. In my past experiences with low Freon I would notice the A/C didn't get as cold as it should but this one stayed cold right up until the compressor shut down. We've driven it 5 days now without a problem so I guess we're good to go. Thanks for the suggestions! I'll post again if any issues persist.
BanditGTP
Member
My a/c has still been acting up intermittently since I last posted. This past weekend it turned on for only the first 5 minutes of a 3 hours ride. A family friend was at a party I was going to and mentioned my problem. He came out to take a look and noticed a little residue around the high pressure valve(Service port located towards the front above the radiator). When he tried to take off the dust cap on the valve, freon just started to leak right out. Apparently the valve itself is bad. When looking in the valve, it looks like a a black button in the bottom. Is that all there is supposed to be there. Can the valve itself be replaced or does the entire line need to be replaced. Hopefully just the valve needs to be replaced.
Mooseman
Moderator
Mounce
Member
Black ball type thing, yes. Like a one way ball valve that is normally opened/closed depending upon pressure on one side in correlation to the other side. I've seen some that were replaceable before but have never payed attention to it on the TB so I can't vouch for it's replacability.
You'll have to take it to an AC shop or mechanic unless you have all of the required tools to pump down the system and refill.
You'll have to take it to an AC shop or mechanic unless you have all of the required tools to pump down the system and refill.
BanditGTP
Member
I just got came back from a shop that said he would be able to replace the shrader valve. After he was trying to work on it for a few minuted he tells me that he might have been mistaken and that the entire hose needs to be replaced. ($310-parts + $200-labor + $80-recharge). He seems to have rounded the edges of the nut so now it's even harder to try to do this myself if I wanted to attempt it. At this point it seems like the shrader valve definitely needs to be replaced so I might just go with vice-grips and see if it will come off.
Tiggerr
Member
Mounce
Member
Did he use the wrong wrench / socket? I'll go out and check mine in a minute. If it has a hex nut on it at the bottom then it's replaceable. It wouldn't have provisions for wrenches if it were built in. At least that wouldn't make sense to me.
BanditGTP
Member
Well I've got good news and bad news. It is replaceable and I got it off myself. The local auto parts didn't have a new one so I went to the dealer and got it for $7. Part# 52458184. Now for the bad news..I put it in and went bad to get it charged. The compressor didn't kick in so beside for the leak I had at the shrader valve, there is still something else causing the compressor to not engage.
Mounce
Member
BanditGTP
Member
Mounce
Member
Pins on the harness right, not the switch? Just want to make sure.
Looked at my high side fitting and to my eye it's removable. Got a ring cut around the nut so idk but it might be right handed thread like the fuel connections on a oxyfuel torch. Not positive.
Looked at my high side fitting and to my eye it's removable. Got a ring cut around the nut so idk but it might be right handed thread like the fuel connections on a oxyfuel torch. Not positive.
Tiggerr
Member
BanditGTP
Member
I had a few spare minutes today to spend on this problem. I started to look into the clutch but it looked like it was going to take more time that I had. I instead started to check the electrical connections. I had already checked the fuses and relay when my problem first started happening and everything appears fine. As soon as I put the fuse back in for A/C, I heard the compressor clutch engage.(the truck was already running). The compressor would keep engaging for a few seconds and then disengage again. After a few seconds, it would repeat the engage/disengage process. I'm assuming when the shop tried to recharge my system, it didn't take a full charge since the compressor wouldn't engage. I then tried shorting the pins on the harness and the clutch engaged and stayed engaged until I removed the jumper. I'm not sure what would have happened to help with the clutch issue both I'm hoping now it magically started working. I'll be going back on Monday to get the system fully charged and hopefully everything will be as good as new.
Wooluf1952
Member
BanditGTP
Member
I tried swapping the relay with another relay when this problem first started happening and had no luck. Yesterday I heard the relay click and then the clutch would engage right away. When the clutch was not working, I don't think I ever heard the relay click so that has me thinking that the problem may fall before the clutch and somewhere in the wiring. If the relay would click but the clutch wouldn't engage then I would say the clutch might the problem. Does this makes sense?
gmcman
Member
- Dec 12, 2011
- 4,673
I had the same situation recently, I removed the shim behind the clutch, re-installed and all is good. If you do this, make sure when it's back together that the front pulley will freewheel when the AC is off. Make sure the compressor won't turn with the pulley indicating insufficient air gap at the clutch.BanditGTP said:
This pretty much band-aids the problem of a worn clutch but it may last a week or a year but it's free to try.
Yes.... if you don't hear the relay, you will never activate the compressor....BUT your assumption that its wiring is probably not good. The PCM decides on when to operate the relay based on the conditions that it "sees". It is more likely that the PCM isn't "happy" with something and thus not operating the relay.BanditGTP said: