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Randall C
Randall C, ASE Master Tech
Category: Mazda
Satisfied Customers: 12803
Experience:  ASE Master Certified, 35 yrs, Diag/Electrical Specialist
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Mazda 3: The belt to my AC compressor is making a squeak noise

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The belt to my AC compressor is making a squeak noise intermittently whether the AC/Defroster is turned on or not. This is the second AC pump that I have installed with the same symptoms. The original one was totally seized up so the pulley wouldn’t turn at all. I thought that maybe it wasn’t the AC compressor at all and that perhaps it could be something on the main belt that was making the noise so I installed a new belt on it but the noise continued. To further isolate the problem I disconnected the power connector to the AC compressor clutch and the noise stopped. This tells me that the AC compressor clutch bearing is OK and so is the main belt and anything on it. What could it be?
Hello, I am Randall. You mentioned 2 compressors installed? one was seized and now a noise has appeared with Ac on correct?

What all work was done when second compressor put on, compressor and recharge?
Customer: replied 5 years ago.

No, two compressors have been installed with this symptom.

I drained the compressor oil by tipping the ports down and turning the compressor center hub to ensure the oil was drained from the pump. Then I added the correct amount of compressor oil before I installed it in the car. Ran the AC system on a vacuum pump for an hour and then charged the system with two 12 oz cans of R134.

Ok, thanks. I have some ideas so please allow me a few minutes to type up and send to you. Thanks
ok, obviously not there to listen etc but, sounds like you have done all the correct steps to help isolate the noise

Heres the problem. Youb have confirmed one bad compressor already. Now on #2 and a noise

I asked as to what all was done for very important reason,. I hate to put % on anything but sure feel safe doing so with this problem

98% of ALl compressor failures are NOt the cause of the compressor but rather a problem somewhere else like small blockage etc. the abnormal pressures put too much strain ont he compressor and over time it begins to fail, running tighter, straining and will cause noises

i feel you have NOT had compressor problems at first but compressor problems due to another problem
1 st off its crititcal to do the drier, maybe expansion valve as well as full system flush anytime a compressor fails. failer to do so will only cause next compresor to fail early

I am failry certain this is what is happening. you need to start quick before new compressor is 100% damaged. you need to change out the parts mentioned, flush system and know for sure with dual guages that you have the correct pressures when done
thsi si all critciacl. no shortcuts. Your compressor are going out because of a blockage causing wrong pressures.

I would unplug it till you are able to perform all the steps.

Hope this all makes sense

BTW: any reman or new compressor will say very clearly that the drier, and flush must be done or voids the warranty. we never just do compressor in the shop. i can only send the info as it really has to be.
Customer: replied 5 years ago.

Rather than going through and replacing parts and flushing the system wouldn't it be prudent to do a high and low side pressure test to see if there is excessive resistance in the system causing high pressure before I break open the system again to flush it and replace parts? If so what pressures should I see on the low and high sides for normal and abnormal conditions?

what is the outside temp you are having where you will test/?
Customer: replied 5 years ago.
60 degrees
I will see if a chart is offered, if not, i will send the range of pressures to watch, back shortly
Customer: replied 5 years ago.
Something else I don't understand is why the compressor turns on intermittently when both the AC and defroster are turned off?
Ok, it can vary but as an average,, the low side should not go lower than around 28 psi and high side no higher than say 215.

If? you have a high side around 220 +/- and a low side say under 30 +/-. this means you have a blockage

be advised that now that compresor is straining, you may not get accurate readings but thinking you will since its not locked up.

You just have to be sure the normal readings are aorund 40 low /200 high. anything in opposite from this means a blockage in most cases
Customer: replied 5 years ago.

I will check it out,

Something else I don't understand is why the compressor turns on intermittently when both the AC and defroster are turned off?

i do not know, That takes more testing. Off is off per say. I have not run into that but.. this would have no bearing on noises, and on second compressor

I just dont know eher to go with compressor on by itself. ther are 2 different systems, full auot or the manual unit. Both have PCm controlled compressor. It gets tricky I suppose if its coming on at time all by itself
Randall C and other Mazda Specialists are ready to help you
Customer: replied 5 years ago.
Ok, I will let you know what the pressures come back at,
Customer: replied 5 years ago.

High side is going up to nearly 250psi and the belt starts slipping. Looks like it confirms your diagnosis.

The dryer is pretty easy to identify but not sure about the expansion valve.

I have not done a flush before. Should I replace the expansion valve before the flush and the dryer after the flush?

sorry for the delay. had to step out. kind of thought so, 250 too high. Do you still need help from my end/?
Customer: replied 5 years ago.

The dryer is pretty easy to identify but not sure about the expansion valve.

I have not done a flush before. Should I replace the expansion valve before the flush and the dryer after the flush?

let me see what I can gather for you. back shortly
I am thinking you are ok breaking loose all the lines you can under hood. Run cleaner through the lines, and through condenser, blow out with compressed air. expansion? may? be the problem but a little harder to get to. so flush what you can under hood, then put in new drier. the darn expansion valve located at lines at evap and hard to get to? i would hold off and see what readings you get with drier and flush. expansion a last effort
Customer: replied 5 years ago.

Sounds good,


LMk thanks
Customer: replied 5 years ago.

It is me again, the dryer was special order so it took a few days. As I am assessing the project I was wondering about the AC compressor? Does it need to be removed? What about the oil in it?



I would see if the compressor can be salvaged. it may be just fine. Just be sure you add a little oil tot he system and the a little to the drier. Bout 1 oz to system and 1 oz to drier and leave oil in compressor alone
Customer: replied 5 years ago.

So I should be OK leaving it mounted to the engine, just disconnect the lines so I can flush them out?

correct. no sense pulling it, oil is in it so just take lines off
Customer: replied 5 years ago.
I was also wondering about the expansion valve. should i try and get some flushing done on it? Maybe flush into the low pressure side so the flow is reversed and maybe dislodge contaminants?
I just dont know. Its in such bad spot to change so.. I say dont. You could get some flush blocked there and will affect the system.
Customer: replied 5 years ago.

Good point, what would you think about just blowing some compressed air in the low pressure side? Or should I just leave that part alone?

you can try but expansion valves are not designed like that so you may not be blowing anything through it. Leave alone for now. that can be a 911/worst case if pressures are not
Customer: replied 5 years ago.
lmk along the way. I am stepping out but back in about 1 hour
Customer: replied 5 years ago.

How do I disconnect the lines to the evaporator? It looks like they are pressed on.


sorry had to step, out. i will see if any info
if the quick disconnect type, youhave to use special tools. Parts stores sell them real cheap. may? not look exact like pic but similar. Just ask for ac line tool. you will get a set os say 4-5-6 of them in plastic not much $

Customer: replied 5 years ago.

If it turns out to be the expansion valve what is involved in replacing it? I assume it is close to the evaporator inside the car, under the dash board.

thus why I was avoiding it up front. You have to remove the HVAc case. Book time is near 4 hours. I dont have a lot of sub info to send. Click HERE
Customer: replied 5 years ago.
Low side is cycling from 18-22psi and high side is cycling from 150-180psi. Vent cooling temperature is 39 deg F.
no bad air temp, but radings are slightly low unless real cold out. i really would like to see the 30-35/ 180-210 range
Customer: replied 5 years ago.
Could it be a little low on freon? How much is this system supose to hold, I thought it was 24oz so I could add another 6oz. Or does the expansion valve look like a problem?
let me check capacity
its really around 20 +/ a little. IMO you can try bumping in a little more to see if you can get pressures to around 30/200 +/- . Outside temp plays big part as well so if chilly out, the readings will look low although charged.the valve would cause a real bad pressure problem you have very good equal pressures, just looks slightly low
Customer: replied 5 years ago.
It is about 57 outside, I put some more freon in and got the pressures up. Something is wrong with my twin gauge low pressure side coupling, when I remove it there doesn't seem to be hardly any pressure behind it. When I put on a couple different gauges they both read a range of about 25-40. The high side is reading about 160-205 now so both sides look better. Even on high max the AC compressor turns of and on with about a 50% duty cycle. Every once in awhile the belt will chirp. Is that normal?
well, your pressures are near dead on for the temp outside, it is cycling, i realize you are very concerned about that compressor so,, keep close eye/ear on it, maybe hit the belt with light mist of WD 40 to help soften it. If it just chirps, may setlle in, if it get slouder, hook up gauges and recheck. 40/205 is nice pressure on the high side, slightly , very lsightly lower is near perfect
Customer: replied 5 years ago.

Sounds good,