Hello all. The AC clutch for my compressor on my 2003 TB does not engage when the button on the digital display is pressed. A little history is there are many electrical gremlins on this TB. The rear wiper does not work along with the heated seats or power seats. The key will not turn back and release. The ignition switch has been replaced. It does now run and goes in gear to be driven. I have looked at all fuses which look fine and have swapped the AC relay. I’ve done the Mode defrost rear defrost three finger reset. I’ve also jumped the low pressure switch. I only have a single R134 gauge for top offs on the low side. The relay does click if I pull it out and re insert it so I assume it’s getting power. I do have a digital multi meter and would like to know if there is a connector I can remove AT the compressor to check for voltage. If there is, how many volts should I be seeing ? I did try to top off the system with a can of R134 without the clutch engaged and the entire can went in. I have read many threads but my problem seems unique because the clutch never engages. I’d appreciate and suggestions. Many thanks in advance.
AC compressor clutch does not engage
- Thread starter Adjustso3
- Start date
Matt
Member
- Dec 2, 2011
- 4,024
If you have the digital climate controls are you sure pushing the button doesn't turn off the AC because it does on my 02 LTZ.
The clutch needs to be engaged to be able to add freon to the system. I'd suggest making sure the AC is turned on and getting a long bladed screwdriver and pushing the clutch to see if you can get it engaged. It may actually be weak magnets that's not allowing the clutch to engage. You can take a shim out to get it closer to the magnet.
The clutch needs to be engaged to be able to add freon to the system. I'd suggest making sure the AC is turned on and getting a long bladed screwdriver and pushing the clutch to see if you can get it engaged. It may actually be weak magnets that's not allowing the clutch to engage. You can take a shim out to get it closer to the magnet.
you don't need to go to the compressor. pull the relay and measure the resistance going towards the clutch coil. That measurement will tell you what condition the clutch coil is in plus tell you if you have a complete path to it. IF the voltage is leaving the relay, it will then find its way to the clutch.... that's how the circuit works. Further, once you have determined that there is a known resistance for the coil, you can jump that contact (ie. the one going to the compressor) and "fire" the clutch to see if it operates.... you don't have to have the engine running, just key in on.
Mooseman
Moderator
Thanks guys for the reply’s. The engine was running when I added the can of R134. The clutch was NOT engaged when it took the whole can. What pins do I jump to bypass the relay ? 87 and 30 ? Also what pins to check for voltage in for 12 bolts and what pins to check the ohms of the coil ? Sorry but I’m just learning on this. So the ignition switch or other gremlins have nothing to do with the AC correct ? When I push the AC button, the display shows off or or the “ AC OFF “ goes away so I assume that is when it is ON. Is there supposed to be a yellow light on the AC button that illuminated like the defrost buttons ? If so, there is no light turning on in mine. Thanks for all your time.
Mooseman
Moderator
The early years used the confusing "A/C OFF" instead. If you don't see that, A/C is on. There is no light for the A/C. Like I said, confusing. Later years show a snowflake when the A/C is on.
If you look on the relay itself, it has a diagram of the connectors. 85 and 86 energizes the relay to activate the switch. There is 12V+ on one of those when the ignition is on.
The switch part is 87 and 30. One of these two has 12V+ all the time. These two you would jump to activate the clutch.
On the underside of the relay, you will see the numbers of the relay connectors, which you would transpose onto the fuse panel.
Don't shove a large probe into the fuse panel's connectors or you could damage them.
If you look on the relay itself, it has a diagram of the connectors. 85 and 86 energizes the relay to activate the switch. There is 12V+ on one of those when the ignition is on.
The switch part is 87 and 30. One of these two has 12V+ all the time. These two you would jump to activate the clutch.
On the underside of the relay, you will see the numbers of the relay connectors, which you would transpose onto the fuse panel.
Don't shove a large probe into the fuse panel's connectors or you could damage them.
Thanks for the reply Mooseman. I used a piece of wire and jumped 87 and 30 of the relay socket. The car clutch did NOT engage. Is this a sign of a bad compressor ? I’m still not sure if the system is over/undercharged with only having the low side gauge and the clutch not engaging. I do notice that the AC relay is on the hot side compared to the other relays even when they are swapped. It does click when it’s inserted.
Mooseman
Moderator
Thanks Mooseman. I’ll give that a try tomorrow since it’s so late and I don’t want to disturb my neighbors. Thanks again.
Yeah you can jumper that ac relay without the engine even running, just on, it should click in (the clutch at the compressor) when you stick the jumper in the relay slots.
I've done the trick that Matt talked about, I used a piece of wood to tap the clutch of the compressor while the engine is running to get the ac compressor to start.
I've done the trick that Matt talked about, I used a piece of wood to tap the clutch of the compressor while the engine is running to get the ac compressor to start.
you need to measure the resistance of the path going to the compressor from the relay socket at the fuse box as shown in the PDF that was posted by mooseman. This will tell you if the connection to the compressor clutch is good. There should be some value of resistance... not zero and not "infinity"/ open.
Hi guys. I’d like from experience which is the easiest access to the compressor connector to check for voltage ? I have a bad back so if I can eliminate trial and error, my back would be most greatfull.
Mooseman
Moderator
if it was my back, I would do the suggested resistance measurement at the fuse box / relay socket. It will tell you more about what's happening from that point ALL the way to the compressor clutch and beyond. A voltage measurement at the connector (removed from the compressor) will only tell you half the story AND give your back a less than wonderful workout.
Thanks guys. Great advice. I’ve been pretty much bedridden and just starting to move around a little more. When is that grass gonna stop growing ? Hopefully I’ll be able to get to the TB soon. So many problems with it and I can only work on it a little at a time. Thanks again for all the assistance. I really appreciate everyone’s time.
You will not be able to reliably know the condition of the A/C System regarding the internal pressures on the opposing High and Low sides of the system without attaching a set of Manifold Gauges via their Service Fittings (Blue for Low Side... Red for the High Side) and observe the differential pressures at rest (they should be approximately balanced with the engine off) and when the engine is running, warmed up and idling... the Low side should descend and the High side should Ascend in pressure levels if the system is running normally.
Once installed Then you can observe each Analog Gauge for the comparative differences and know for certain whether or not the system is either under-filled ...or over-filled with R-134A Refrigerant. Harbor Freight carries an inexpensive Auto Manifold Gauge Set that will suit this purpose to a "T".
Regarding what you are dealing with concerning "Back Problems"... the BEST 4 Velcro Panel Back Support... EVER... is made by "MUELLER" and available on Amazon. I would not be able to set my cane down and do any work around vehicles without having mine on at all times:
https://www.amazon.com/dp/B00267SFK2/?tag=gmtnation-20
Once installed Then you can observe each Analog Gauge for the comparative differences and know for certain whether or not the system is either under-filled ...or over-filled with R-134A Refrigerant. Harbor Freight carries an inexpensive Auto Manifold Gauge Set that will suit this purpose to a "T".
Regarding what you are dealing with concerning "Back Problems"... the BEST 4 Velcro Panel Back Support... EVER... is made by "MUELLER" and available on Amazon. I would not be able to set my cane down and do any work around vehicles without having mine on at all times:
https://www.amazon.com/dp/B00267SFK2/?tag=gmtnation-20
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Thanks MRRSM. I think I better get a set of gauges. I assume since the low pressure switch was jumped and the compressor didn’t turn on that it’s not low on R134A. Will a high reading be possible since the clutch is not engaging ? I was able to take it for a drive today to get some fuel. It was nice to drive it again. It kinda sounds like a bus when it’s accelerating. I don’t remember this sound before. It may also need fresh power steering fluid or a new pump because the steering wheel has to be muscled to turn at low RPM. I also notice the ABS acting up when applying the brakes through the pedal. It may be because it’s been sitting for so long. A big thanks on the heads up on that back brace. Not many people recommend back braces. I’ll definitely be ordering one very soon.
Mooseman
Moderator
No. It has to be running. The high pressure switch could be defective.
Please don't mix issues. Start a new thread(s) for the new issues.
Duane from "RealFixesRealFast" puts on an Excellent Clinic that fully explains How the High and Low Pressure Switches function in two Generic GM A/C Systems that will greatly improve your understanding of How these A/C System Circuits Work... and also...How to Diagnose one that is having problems with either of these two Logic "Circuit Interrupter" Switching Mechanisms:
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Thanks guys. Can the high pressure switch connector be jumped like the low pressure switch connector to see if the clutch will engage ? Where is the high pressure switch located ? Thanks again.
Never... Ever attempt to bypass the A/C High Pressure Cut-Off Switch. It is designed to prevent a catastrophic, explosive rupture of the A/C System.
You really need to get off of “The A/C Guessing Game Diagnostic Carousel” and hook up the suggested A/C Manifold Gauge Set next...and see what the Hell is actually going on inside of your A/C System before you take another step. Trying to access and Test the High Pressure A/C Switch on your SUV before hand will be a lot like trying to take your pants off over your Head… to remove your “T” Shirt.
At 5:24 and again during re-assembly at around 13:50 in this Youtube Video… you can catch a few glimpses of the location of the A/C High Pressure Switch where it screws into the back High and Low Line A/C Lines Connection Manifold at the top back of the Compressor. You can’t just reach down inside there to run DMM diagnostics on the A/C HP Switch with ease here… GM never wants any problems like these getting solved by the Owners.:
But Jesus Palomino… If you have to go this deep into gaining access to the A/C HP Switch… and if you have confirmed and are convinced that the A/C Condenser Coils and Orifice Filter Tube are NOT completely Clogged with Crap… Hell… you might as well R&R in a Brand New OEM A/C Compressor after flushing the High and Low Lines and the Condenser Coils first with Compressed Cans of A/C Flush and installing a Brand New Accumulator; each of them pre-filled with 2-3 Ounces of Fresh PAG 46 Oil.
Then likewise… pre-fill the Brand New. OEM Quality Compressor with 2-3 Ounces of PAG 46 Oil, cycle that Oil at LEAST (10) Times by manually turning over the Compressor Innards and then install the damned thing and be done with it. Do NOT Flush the A/C High and Low Lines and Condenser Coils filled with Old Crap and Metal Particles from an Old Damaged Compressor AFTER installing a Brand New Compressor ...unless you want to wind up having to buy TWO of them when all of that MUNG enters the New Compressor and destroys it. You should Flush those A/C Lines... AFTER you first pull out the Orifice Filter Screen Tube and Isolate the Accumulator-Drier and Evaporator Coil from the rest of the System. Then discard the Old Accumulator-Drier and install a Brand New one filled with 2-3 Ounces of PAG 46 Oil.
One final thought here is that you should NOT follow this Yo-Yo’s procedure of willfully installing a Sub-Par Compressor and then also failing to R&R the Orifice Tube AND the Accumulator on purpose as a matter of course. His customer-owner here will be back to see him in about five to six weeks after he did this otherwise instructional Video to find out why his A/C blows Hot Air so soon after this Repair Job. If you wind up doing this job… RTFM! And follow it Chapter and Verse for this R&R;
HVAC High Pressure Switch Basic DMM Diagnostics:
https://www.youtube.com/watch?v=JXWqWt1qot
You really need to get off of “The A/C Guessing Game Diagnostic Carousel” and hook up the suggested A/C Manifold Gauge Set next...and see what the Hell is actually going on inside of your A/C System before you take another step. Trying to access and Test the High Pressure A/C Switch on your SUV before hand will be a lot like trying to take your pants off over your Head… to remove your “T” Shirt.
At 5:24 and again during re-assembly at around 13:50 in this Youtube Video… you can catch a few glimpses of the location of the A/C High Pressure Switch where it screws into the back High and Low Line A/C Lines Connection Manifold at the top back of the Compressor. You can’t just reach down inside there to run DMM diagnostics on the A/C HP Switch with ease here… GM never wants any problems like these getting solved by the Owners.:
But Jesus Palomino… If you have to go this deep into gaining access to the A/C HP Switch… and if you have confirmed and are convinced that the A/C Condenser Coils and Orifice Filter Tube are NOT completely Clogged with Crap… Hell… you might as well R&R in a Brand New OEM A/C Compressor after flushing the High and Low Lines and the Condenser Coils first with Compressed Cans of A/C Flush and installing a Brand New Accumulator; each of them pre-filled with 2-3 Ounces of Fresh PAG 46 Oil.
Then likewise… pre-fill the Brand New. OEM Quality Compressor with 2-3 Ounces of PAG 46 Oil, cycle that Oil at LEAST (10) Times by manually turning over the Compressor Innards and then install the damned thing and be done with it. Do NOT Flush the A/C High and Low Lines and Condenser Coils filled with Old Crap and Metal Particles from an Old Damaged Compressor AFTER installing a Brand New Compressor ...unless you want to wind up having to buy TWO of them when all of that MUNG enters the New Compressor and destroys it. You should Flush those A/C Lines... AFTER you first pull out the Orifice Filter Screen Tube and Isolate the Accumulator-Drier and Evaporator Coil from the rest of the System. Then discard the Old Accumulator-Drier and install a Brand New one filled with 2-3 Ounces of PAG 46 Oil.
One final thought here is that you should NOT follow this Yo-Yo’s procedure of willfully installing a Sub-Par Compressor and then also failing to R&R the Orifice Tube AND the Accumulator on purpose as a matter of course. His customer-owner here will be back to see him in about five to six weeks after he did this otherwise instructional Video to find out why his A/C blows Hot Air so soon after this Repair Job. If you wind up doing this job… RTFM! And follow it Chapter and Verse for this R&R;
HVAC High Pressure Switch Basic DMM Diagnostics:
https://www.youtube.com/watch?v=JXWqWt1qot
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wow, it really amazing me at what people will attempt to go around very easy checks using a simple meter. Anyways, good luck and best wishes to your back.
Hi guys. As instructed, I did get my meter out and probe the AC relay. With the TB running, pins 85 and 86 had 13.94 volts. 87 and 30 showed 650 ohms. I think the ohms was set at 25K. I ordered that back brace. I can’t wait for it to come in and try it.
you are testing the socket ONLY with the relay removed... right? you don't need to have the truck running... the contacts in the socket of interest are not the one you measured the voltage on... those are going to the battery. As stated earlier, you are interested in the path going from the socket to the compressor (clutch) as shown in the posted diagram. You measure resistance from a KNOWN ground point ( battery negative cable) to the contact point of interest, in the fuse block socket.
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Mooseman
Moderator
Did you try what I bolded above? This would tell you quickly if the compressor clutch is functional. If it doesn't, try pushing on the clutch face towards the pulley. If it does, then take the clutch apart and remove the shim on the shaft.
https://gmtnation.com/forums/threads/air-conditioner-clutch-shim-removal.17403/
I think he indicated that he did that back in post #7. Of course, knowing how finicky the fuse box contacts are, "success at jumping" may not be readily seen... maybe. His resistance measurements don't look so good but then again, not sure what he actually did to achieve those as doing a "system powered" while measuring resistance is technically incorrect.
Mooseman
Moderator
He didn't check for power at 87/30. One of these two has to have power to energize the clutch when they are jumped. Or got the pin numbers wrong. He said 85 and 86 have 12V which doesn't make sense.
you are right about that check. As far as the "85 and 86" showing "12v"... it does make sense "potentially" (pun intended) because if there was no ground at the control point, then his voltage measurement would show basically the same potential at both points on the relay coil (if it is a coil). Anyways, I guess the "simple test" isn't so simple if you don't know how to measure electrical parameters. 
Further, I suspect he just did a resistance measurement across the 87 / 30 contact... maybe ... although anything is possible at this point without seeing "his hands".
Actually, re-reading his "measurement post", I suspect he also measured across 85 and 86 as opposed to measuring each of those contract points with respect to ground.
Further, I suspect he just did a resistance measurement across the 87 / 30 contact... maybe ... although anything is possible at this point without seeing "his hands". Actually, re-reading his "measurement post", I suspect he also measured across 85 and 86 as opposed to measuring each of those contract points with respect to ground.
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Thanks for the reply guys. It appears I’m a little confused with how I should be checking the AC relay socket. With not damaging the socket opening in mind, I put two separate small wires into 85 and 86 and got 13 plus volts. I then took the same two wires and put them in 87 and 30, switched my meter to ohms and got 650. I’m not sure if it matters what I have the ohms set at because we’re just looking for a break in the wiring or compressor right ? Am I checking this wrong ?
... well that's not really how to do the measuring. The "piece of wire" is fine, its what points you connect your meter to for a measurement. Normally, for voltage, you measure voltage from a KNOWN ground point (black lead) and the red lead touches the point, contact, pin you are testing. In your case, you lucked out and the 86 (or 85) had a ground on it and the other pin had the voltage. You would then state that pin xx has "12v".... not pin 86 and 85 have 12v which implies that both had voltage on them... which is likely NOT true.Similarly, for resistance, as I already mentioned, you do this measurement WITHOUT any voltage in the system as the meter provides its own. IF there is other voltage in the system, the resistance reading will likely be wrong as the meter can't determine where the "extra power" is coming from. As with voltage test, you place the black lead on the "far end" of the circuit that you want to get a resistance reading... in this case, we look at the circuit that was posted and you see that the "far end" is the "ground" as identified below the clutch "symbol". The red lead goes at the socket / pin / "test wire" of 30 . This measures the resistance from the socket all the way thru the clutch to the ground. That is the value that we need to know. IF it is zero (unlikely), it means there is a short in the wiring or clutch coil. IF it is "infinitely" / very high, that likely means the wiring is broken or the clutch coil is burned out. Some low value is likely good and you can start looking elsewhere for your problem. That's the "1 minute lesson" of which there is lots of videos and better explanations for on the net. Hope that is clear.
OK, now I get it. Each pin in the socket is individual. Understanding more how the circuit works makes more sense. It’s just not an off/on like a house switch. I’ll have to wait for it to stop raining and I’ll post my readings. By the way, I have tried to push the clutch in with a long pry bar with zero results. Thanks again. I really appreciate everyone’s time.
Mooseman
Moderator
You’re so right Mooseman. I hate to make excuses but my head has been spinning lately with the TB, my health, news of GF breast cancer, and the passing of my mother. I’m so greatfull to have you guys keeping me straight with each and every one of this TB problems. It’s amazing how an overloaded plate of stress can make you appear brain dead. I have no problem keeping everybody else’s cars on the road but by the time I get to my TB my head just draws a blank lol. I big thank you again. I appreciate all of you.