Acura RSX A/C compressor overheats

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Joined: Mon Jul 31, 2017 6:37 pm

Acura RSX A/C compressor overheats

Postby avlcat » Mon Jul 31, 2017 7:08 pm

New member here looking for help diagnosing the AC problem.

I have 2003 Acura RSX Base with AC compressor overheating. The car AC system was completely original until now; nothing have been replaced or fixed to my best knowledge. The AC worked fine until this year.

AC works fine and blows cold air when the car is cold. After some time the system starts blowing only hot air. The time until AC malfunctions greatly depends on outside temperature - if it is 70F or below it may work fine for my entire commute (1 hour); if outdoor is 80F it may run for 20 minutes then stop; if outside is 100F it may take just a few minutes before it stops blowing cold air. After some time (5-10 minutes) it starts blowing cold air again for another 5-10 minutes, then the cycle may repeat.

These cars have thermal protection device on the compressor and it is definitely trips cutting power to the compressor clutch coil. I measured voltage after compressor clutch relay and it is present (12V); measured voltage after the protection device and it is 0. I also tested the resistance between the thermal protector and ground (with coil in the circuit) and it is about 3 Ohm when compressor is cold and infinite when compressor is cold.

The compressor clutch relay and fuses are tested and good.

The low side pressure seems normal, around 30. The high side pressure is also seems normal on idle RPM, about 180. However when RPMs are increased to 2500-3000 the high side pressure starts to increase too, goes to about 250 and then thermal protector shuts off the compressor.

Here is what I did trying to fix the issue:

1. Replaced thermal protection sensor with brand new Honda part. No results.
2. Replaced condenser fan. The original one was working but seemed to rotate not fast enough. No results.

At this point I decided to open up the system and replace expansion valve suspecting it has stuck closed or partially closed. I had a local shop to evacuate the refrigerant. They said the system was low on refrigerant; they only evacuated 6 oz of refrigerant while the system capacity is 18-19 oz.

After evacuating R134A I did:

3. Replaced expansion valve
4. Replaced receiver/drier
5. Cleaned evaporator coil. It was not too dirty but I did that anyway
6. Replaced condenser as original was in rough condition after 14 years in service...
7. Cleaned radiator to make sure the airflow through radiator/condenser is not blocked.
8. Replaced radiator fan

When replacing the parts, I also used new o-rings everywhere and added PAG46 oil to new condenser and drier per service manual. Unfortunately I did not specifically checked for dirt inside the hoses/pipes and did not flush the hoses but I did not notice anything obvious. There is no visible dirt in the original expansion valve and unfortunately I did not keep the drier so I can't check if there was anything inside.

Once I finished with this I had the same shop to evacuate the system and charge it with correct amount of refrigerant.

The system worked fine for few days (it was relatively cool outdoors these days), but started to show the same issue again.

Checking it further I suspected leak in the low port service valve. It makes slight hissing sound every time I remove the cover cap. I brought the car to the shop which did the recharge and they agreed to replace both service port valve cores and recharge it again. When I picked the car up they said the system lost couple of ounces of refrigerant. To be honest, I doubt they actually did what they said because there was no any paperwork and the low service port still does that hissing sound when cap is removed, but maybe this is normal?

Anyway, still no results. The system still quickly overheats when outdoor temperature is above 70-80F. I even added the LED light connected to the compressor thermal protector so I can see how the system cycles the compressor while I am driving. When outside is below 70F it cycles compressor on for 8-10 seconds every 20 seconds and everything seem normal. However when outside is 80F and above the ON cycle time increases and eventually it stays on for a long time and compressor overheats again. When the LED signals the compressor in on but warm air blows the compressor clutch definitely not engaged; I confirmed by looking on it. It will engage again after few minutes at idle, but quickly disengages again.

I checked the evaporator temperature sensor thinking that it may have failed and caused evaporator to freeze up and block the refrigerant flow. It tested right in the entire temperature range from 32F to 86F. Also checked air mix door actuation motor and it is also good.

What else could cause the high side pressure to rise and compressor to overheat?

Posts: 1
Joined: Mon Aug 07, 2017 7:10 am

Re: Acura RSX A/C compressor overheats

Postby coolmedown » Mon Aug 07, 2017 7:26 am

I suspect it's the compressor clutch assembly. My 2008 Honda CRV was showing the same exact symptoms your car is displaying. Only difference was a slight rattle sound when the clutch engaged on my car. The problem started happening last summer. It got worse as time went on. But got a little better when outside temps went down. This spring when I tried to use the AC the clutch didn't engage at all (radiator/condenser fan engaged though). Did a quick pressure test and there was pressure. Went to local mechanic and requested the whole compressor be replaced. After replacement, AC compressor engaged afterwards.

But there is a new problem. AC is not as cool as it once was and compressor doesn't disengage unless I hit the AC button to shut off. I'll have to verify performance issues.

But anyways, I think your compressor clutch might be out of spec now. The clutch coil might not be getting energized as it gets hotter.
Posts: 2
Joined: Mon Jul 31, 2017 6:37 pm

Re: Acura RSX A/C compressor overheats

Postby avlcat » Wed Aug 09, 2017 11:40 am

Just a quick update. The issue was not with AC system but with alternator. On these cars the alternator is located right above the compressor and the thermal protection sensor is on top of compressor, so it is like sandwiched between compressor and alternator. The charging system warning light came on few days ago, so I checked the alternator temperature and it was around 240F. This is exactly where the ac thermal protection sensor is supposed to trip and open the coil circuit.

I replaced the alternator (yes, it was indeed dying; one slip ring was worn and corresponding brush was worn too). AC works fine since then. It just been couple of days and temperatures are around 75F now so the results are not conclusive yet, but so far so good...

The only (new) issue is that I noticed brief "moaning" sound sometimes. Just for a second or so. It happens when AC cycles on, only when engine RPMs are low (idle or stuck in traffic). It also seems to happen only when engine is warmed up; I did not notice it when car was cold. And it does not happen every time; just occasionally. Not sure what it is and if it is sign of any problem, but if any suggestions would be appreciated.

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