Dr Feelgood

I'm looking to replace my AC compressor but it seems that the Denso 471-0127 and 471-0128 are used almost interchangeably. The 85.5 and up 944's and 968's use 471-0128 with some odd exceptions. Some places say that the 944 S2 uses the 471-0127 but what I find isn't consistent. Other places say that they are actually interchangeable. Does anyone know what the difference between these compressors are if any? I have a 1991 944 S2.

griffiths

85/2 through 92 was R12 from the factory, 471-0127

93 onward was R134a from the factory, 471-0128

R134a uses a different refrigerant oil and o-ring compound

944 AC Parts

Dr Feelgood

Thank you that is excellent information!

So does that mean that they are identical other than the pre-loaded oil and O-rings? In other words if I have an R134a system on a 1991 I should be getting the 471-0128?

griffiths

Usually, DENSO, does have oil in their compressors.
The question is (and with any compressor remani'd, new, or whatever) how much ?

The best thing to do is to find a clean coffee can. Take the shipping plates (plates covering the ports where you will be swapping over our hose manifolds, don't mix up your hose manifolds) off. Turn the compressor over the can and rest it on it. Turn the outer hub (with the shaft nut on it) a dozen times in each direction slowly. Tilt the compressor port to starboard. Get out as much of the oil as you can in the can.

If you car was converted to R134a the question is did they use R134a compatible oil, ESTER or PAG. You want to try to use the same type. If you did not do the conversion look for a blue R134a sticker in the engine bay, it lists the type of oil used (if they did it properly). Look at service records. Call the shop that did it, etc.

You will need to put back into the compressor or the system 4-6 oz of fresh refrigerant oil.

You should be replacing your receiver drier. Replace as many of the systems o-rings that you can reach (the expansion valve on the evaporator is the pita).

If you are replacing a compressor because your's locked up, froze or imploded, you will want to liquid AC flush the hoses, condenser and evaporator before R&Ring the compressor; in that case you will want to put back in 6 oz min of refrigerant oil in your year car.

Dr Feelgood

I can get the 471-0128 cheaper so if it physically will hook up correctly you are right, I can just change out the oil if needed. Just want to confirm that they are interchangeable. Is that correct?

griffiths

either one will work, what ever makes you feel good

Dr Feelgood

I will be changing the compressor, drier, and flushing the condenser. I will use ester oil (POE). There seems to be more conflicting data on how much oil the system takes. The service manual says 80ml +or- 20ml ( 2.7oz +or- 0.7oz) which I assume is for the original r12 system. However, this technical service bulletin says that the r134a converted system requires a different amount of oil, 130ml +or- 20ml (4.4oz +or- 0.7 oz)

http://www.944time.com/porsche/2005images/944_ac.pdf

I guess I'm assuming I use the the amounts on the TSB and I'm assuming that more is needed because of the differences between PAG and mineral oil. I'm hoping that the ester oil will be closer to the capacities listed for the conversion in the TSB. With only replacing the compressor, drier, and flushing the condenser would 4oz seems reasonable as there will still be some residual oil in the system?

griffiths

Ideally, in a perfect world, you would liquid flush all the lines, condenser, evaporator with TEV removed.

We have assisted hundreds of 944/951 clients over the past 18 some years with R134a conversions, and for your year and model we have suggested 5-6 oz of ester without any performance issues.

The TSB suggests PAG, however if you have residual mineral oil the ester tends to mix better than the PAG

WolfeMacleod

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I was looking into this recently, as my 924S A/C compressor has failed.
I'm on the phone with Denso right now. They tell me that the 0127 compressor is for r134A.

Dr Feelgood

I used the 0128 in my 944 S2 with r134a and it works great. I did change the oil out of the compressor to ester oil so you would just have to confirm what oil it ships with.