2008 AC compressor wont engage

PhotoTek · Jun 19, 2021

The AC in our 2008 EX-L worked fine last night, but today, it started blowing hot air during my wife's errands. I have checked the fans and they all blow at various speeds, the back blower blows at all speeds but air only comes out of the vent under the 3rd row - no air at all from roof vents, even when I cycle the mode switch. I located the relay in the box under the hood, it 'appears' okay, but I am not sure how to test it. If there are other fuses to check, I don't know what they are or where they are located.

The only difference I know of between yesterday and today is that I installed a VCM Tuner II this morning, by the book. I sent an email to the info@ address to see if they have any information, but I doubt it has anything to do with it.

Any suggestions, ideas, etc. are VERY WELCOME - the sooner the better, since we are on the Gulf coast of Texas.

marvinstockman · Jun 19, 2021

You could have a bad relay (some of the other relays are the same and can be switched), a bad compressor clutch, and low R134a, plus a thousand other things.

Try youtube for troubleshooting an AC system.

WiiMaster · Jun 19, 2021

Been there with A/C issues in Texas.

First thing you want to do is make sure the A/C clutch relay is made by Mitsuba and not Omron (it will say on the top of it). If you have an Omron relay, that could be your problem. Get the Mitsuba relay from Honda. It costs ~$20. You could also try swapping out one of the other two black relays that are closer to the back of the engine bay. But at some point you'll want the Mitsuba relay.

If that doesn't help and your system has not been recharged in many years, get the system professionally evacuated and recharged, as you could be low on refrigerant.

After that, you'll want to start diagnosing components.

Your rear air issue is likely a rear mode control motor. It's an extremely common issue. You can run the AC system self test using the diagram @hpark21 will provide sooner or later to verify this.

PhotoTek · Jun 19, 2021

After some testing and YouTubing, I think I have a compressor clutch that is going out. The issue has been hit and miss, until today. Now it's more miss than hit. After sitting for an hour or two, I went out and started the car, and the AC will cycle on and off with the AC switch.

Does anyone have another theory?

Has anyone replaced the clutch and can tell me the ins and outs of that process?

Thanks in advance.

thscott · Jun 20, 2021

PhotoTek said:
After some testing and YouTubing, I think I have a compressor clutch that is going out. The issue has been hit and miss, until today. Now it's more miss than hit. After sitting for an hour or two, I went out and started the car, and the AC will cycle on and off with the AC switch.

Does anyone have another theory?

Has anyone replaced the clutch and can tell me the ins and outs of that process?

Thanks in advance.

It is more likely that you have a clutch relay issue. Rule that out first.

GoHerdMan · Jun 20, 2021

Swap the ac relay under hood first to see if that's it. Common....but could also be worse

hpark21 · Jun 20, 2021

WiiMaster said:
Been there with A/C issues in Texas.

First thing you want to do is make sure the A/C clutch relay is made by Mitsuba and not Omron (it will say on the top of it). If you have an Omron relay, that could be your problem. Get the Mitsuba relay from Honda. It costs ~$20. You could also try swapping out one of the other two black relays that are closer to the back of the engine bay. But at some point you'll want the Mitsuba relay.

If that doesn't help and your system has not been recharged in many years, get the system professionally evacuated and recharged, as you could be low on refrigerant.

After that, you'll want to start diagnosing components.

Your rear air issue is likely a rear mode control motor. It's an extremely common issue. You can run the AC system self test using the diagram @hpark21 will provide sooner or later to verify this.

Ha ha.. Maybe this should be in a sticky somewhere:

marvinstockman · Jun 20, 2021

Just for fun, make sure the AC relay is swapped or replaced.

If it is the clutch itself, it is because it is 13 years old, and the clutch gap is too wide. Remove outer clutch plate, and remove one of the spacer washers. If you have two washers, remove the thinner one. You should be good to go. Note, when the engine is cold, the gap is small enough so that the clutch can engage. As things heat up, the gap increases, and the clutch cannot pull in the plate.

Search around for repair videos on clutch gap.

jabraham2005 · Jun 20, 2021

PhotoTek said:
After some testing and YouTubing, I think I have a compressor clutch that is going out. The issue has been hit and miss, until today. Now it's more miss than hit. After sitting for an hour or two, I went out and started the car, and the AC will cycle on and off with the AC switch.

Does anyone have another theory?

Has anyone replaced the clutch and can tell me the ins and outs of that process?

Thanks in advance.

My 2005 had the same issue. Try a different relay first and tule that out. My was the clutch and stator set. Replaced both and it fixed the problem.

PhotoTek · Jun 20, 2021

WiiMaster said:
Been there with A/C issues in Texas.

First thing you want to do is make sure the A/C clutch relay is made by Mitsuba and not Omron (it will say on the top of it). If you have an Omron relay, that could be your problem. Get the Mitsuba relay from Honda. It costs ~$20. You could also try swapping out one of the other two black relays that are closer to the back of the engine bay. But at some point you'll want the Mitsuba relay.

If that doesn't help and your system has not been recharged in many years, get the system professionally evacuated and recharged, as you could be low on refrigerant.

After that, you'll want to start diagnosing components.

Your rear air issue is likely a rear mode control motor. It's an extremely common issue. You can run the AC system self test using the diagram @hpark21 will provide sooner or later to verify this.

The relay appears to be Denso with a Toyota stamp on it. I believe I identified the correct one and that it is working because as the AC is turned on and off, I can feel/hear the clicking in the relay (the middle, black relay on the row nearest front of vehicle). There are two Omron relays on the back row of the same fuse box. I will take your advice, however, and secure one from the dealership on Monday.

Thanks

PhotoTek · Jun 20, 2021

marvinstockman said:
Just for fun, make sure the AC relay is swapped or replaced.

If it is the clutch itself, it is because it is 13 years old, and the clutch gap is too wide. Remove outer clutch plate, and remove one of the spacer washers. If you have two washers, remove the thinner one. You should be good to go. Note, when the engine is cold, the gap is small enough so that the clutch can engage. As things heat up, the gap increases, and the clutch cannot pull in the plate.

Search around for repair videos on clutch gap.

Thanks for the advice. After the van sat for a hour or two, I went out to test again and the AC turned on right away and blew cold air, so I suspect the clutch set is the fault, but did not think of trying to narrow the gap by subtracting shims. I did see a video on the clutch repair and it mentioned the shims and even gave a gap tolerance (.012-.024 Cold, I believe). Please correct me if that gap measure is incorrect.

PhotoTek · Jun 20, 2021

thscott said:
It is more likely that you have a clutch relay issue. Rule that out first.

That is the easiest and cheapest fix, I agree. I did feel/hear the relay click when the AC was turned on (but would not engage), so that seems to me like it is trying to work, but not getting the results from the clutch coil.

Do relays act intermittently when they begin to fail, or are they usually working until they fail (Good then No Good) permanently?

Thanks for the help.

geotek · Jun 20, 2021

PhotoTek said:
That is the easiest and cheapest fix, I agree. I did feel/hear the relay click when the AC was turned on (but would not engage), so that seems to me like it is trying to work, but not getting the results from the clutch coil.

Do relays act intermittently when they begin to fail, or are they usually working until they fail (Good then No Good) permanently?

Thanks for the help.

When you hear/feel the relay click that means you have applied power across the coil of an electro magnet armature and maybe the contacts attached to it have closed to energize a given circuit. These contacts can be good, bad, burnt or dirty. If when they energized you heard the compressor run then you know they worked and passed enough current to energize the clutch coil. Now, depending on the condition of all the connections in this entire circuit it can be intermittent, good, or fail permanently. From the relay end there are flat tabs that plug into sockets. Then the tabs are soldered into an epoxy board with copper lines connecting it to the coil of the relay. The relay contacts are soldered to tabs that plug into the relay socket.
The relay socket is connected to a plug that plugs into the compressor clutch socket on the compressor. This socket is connected to the coil that provide the field that energizes the clutch plate. So, with the correct gap, verify the continuity of this circuit and your compressor will rotate.

PhotoTek · Jun 20, 2021

hpark21 said:
Ha ha.. Maybe this should be in a sticky somewhere:
View attachment 162500

Thanks for the input - I didn't even know the AC could diagnose itself. I tried it and what it indicated is H, or what looked to me like H and a small 1, BUT with NO "Auto" indicator, so it is either "a short in the Evaporator Temperature Sensor circuit (if it had an AUTO indicator), OR a "problem in the rear air mix control linkage, doors or motor." The second seems to make sense because of the lack of roof vent output as described in another of my posts. I am not sure what to make of the ETS circuit option.

I have a feeling that I have two problems which may be unrelated: a rear air mix issue AND a compressor/clutch/relay issue.

Your thoughts?

PhotoTek · Jun 20, 2021

geotek said:
When you hear/feel the relay click that means you have applied power across the coil of an electro magnet armature and maybe the contacts attached to it have closed to energize a given circuit. These contacts can be good, bad, burnt or dirty. If when they energized you heard the compressor run then you know they worked and passed enough current to energize the clutch coil. Now, depending on the condition of all the connections in this entire circuit it can be intermittent, good, or fail permanently. From the relay end there are flat tabs that plug into sockets. Then the tabs are soldered into an epoxy board with copper lines connecting it to the coil of the relay. The relay contacts are soldered to tabs that plug into the relay socket.
The relay socket is connected to a plug that plugs into the compressor clutch socket on the compressor. This socket is connected to the coil that provide the field that energizes the clutch plate. So, with the correct gap, verify the continuity of this circuit and your compressor will rotate.

So, are you saying that I could hear/feel the relay click, but it still may not be working?

marvinstockman · Jun 20, 2021

First, a relay is two things. The first is the solenoid which engages the contacts, and then there are the contacts. If the contacts are burned, the solenoid can engage the contacts, but the contacts won't make contact.

Just use one of the other similar relays for a test.

Regarding clutch gap, I've never done it on an Ody, just on a two Saabs and a Ford. Search around for the recommended gap, and measure the current gap when everything is cold. To get a clear shot at the clutch, you may have to remove the right front wheel and fender liner.

WiiMaster · Jun 20, 2021

PhotoTek said:
Thanks for the input - I didn't even know the AC could diagnose itself. I tried it and what it indicated is H, or what looked to me like H and a small 1, BUT with NO "Auto" indicator, so it is either "a short in the Evaporator Temperature Sensor circuit (if it had an AUTO indicator), OR a "problem in the rear air mix control linkage, doors or motor." The second seems to make sense because of the lack of roof vent output as described in another of my posts. I am not sure what to make of the ETS circuit option.

I have a feeling that I have two problems which may be unrelated: a rear air mix issue AND a compressor/clutch/relay issue.

Your thoughts?

I do agree that you have two separate issues. However, I'd say it's more important to figure out the main A/C issue first before you have to start removing the rear trim panel for the mix motor issue.

Relays are cheap. So I do think you should get a Mitsuba one from the dealership to eliminate it. If your A/C blows very cold when it does work, your refrigerant is probably fine. So eliminate the relay, then maybe go diagnosing the clutch.

Aye_+ · Jun 22, 2021

I didn’t want to create a new thread on a very similar topic but I also don’t want to hijack this thread buuuuuuttt……
The clutch on my 06 is also not engaging so I went ahead and ordered some relays even though I rotated the three under the hood to see if one of them would get it going, It didn’t.
I took it to a shop out here and he charged the AC but that still didn’t get it going. He said for another $120 he can do a full diagnosis but I don’t think I want to pay that. Based on some of the threads on here, it seems like replacing the clutch and coil can be hit or miss if not installed correctly (ie. clutch gap or clip removal/installation) Also, I’m not sure on what brand of part to purchase and it’s very possible that those parts aren’t even defective.
That being said, if the new relays don’t work, I can get a denso compressor online for $250 tax and shipping. Should I buy that or buy a random clutch & coil to do the swap? I’m not good at testing things as I only have a multimeter and can barely work that so the compressor might still be salvaged but I’m pretty good at swapping thing out. What do y’all think?

Eric Hill · Jun 22, 2021

The clutch will not engage if the freon is low. There is a pressure switch in the circuit

Ed2013 · Jun 22, 2021

First thing I like to do is measure the high / low side pressures to see if your Freon levels are ok. If they are low the compressor can cycle. It’s an easy test if you have the gauges. If you don’t, hopefully you know someone who does. It‘s sure cheaper then replacing parts.

2008 AC compressor wont engage

PhotoTek

marvinstockman

WiiMaster

PhotoTek

thscott

GoHerdMan

hpark21

marvinstockman

jabraham2005

PhotoTek

PhotoTek

PhotoTek

geotek

PhotoTek

PhotoTek

marvinstockman

WiiMaster

Aye_+

Eric Hill

Ed2013

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