944 A/C Condenser Leak

[Tom]

Well I finally got the replacement condenser in the car and re-charged the system today. (This time with all new rubber mounts, yet new o-rings, and yet another new receiver drier.) This is the aluminum parallel flow unit from Cooler Classics on eBay. The first one had a leak, but they replaced it no questions asked, and it just took me a few weeks to install the replacement as the old Mercedes was hogging the lift to fix a leaky cooling system.

After checking to make sure it held vacuum (it did, over night) and then pulling a vacuum for 45 minutes, I added 29.5 oz of r134a. The factory TSB on converting to r134a (Dec. 19, 1995) calls for 860g of r134a, which is a little over 30.33 oz. Griffiths recommended a similar amount when using r134a with its condenser, so that was my target, but I opted to stop short of that because my pressures looked good and I was getting seriously cold temps from the vents even on the highest fan speed. I went for a 2 mile test drive and had to turn the a/c down because it was getting frigid in the car. I got low vent temps before, but now it seems to hold those temps even when the fan is on full blast. Seriously happy with the results so far, but I won't claim success for another few weeks until I'm sure this new condenser can hold the pressure. If it does, I'll whole-heartedly recommend this condenser for anyone running r134a.

[icb]

Hey Tom, your comment about how cold your vent temps are now made me look this condenser up in ebay. I was pretty surprised to see a picture of a fin and tube, and not a modern micro-channel condenser. Is this really what you received, a new fin and tube type condenser?

[Tom]

Hey Tom, your comment about how cold your vent temps are now made me look this condenser up in ebay. I was pretty surprised to see a picture of a fin and tube, and not a modern micro-channel condenser. Is this really what you received, a new fin and tube type condenser?

No, you can see it in post #7 above. Cooler Classics makes lots of coolers, so maybe you were looking at a different one? This is the one I got -- parallel flow...

https://www.ebay.com/itm/266678393896?_ ... -ZA&edge=0


For posterity, since eBay links don't last long...

cccondense.jpg (1.06 MiB) Viewed 691 times

[whalenlg]

Hi Tom - did you record ambient and vent temps?

[Tom]

Hi Tom - did you record ambient and vent temps?

Ambient was 81. I did not measure vent temps this time. It was ice cold at the vents, so knowing the specific number didn't seem to add to the equation. I'll put a thermometer in the vent today though, for anyone interested.

[icb]

OK I see it now, Tom, thanks.
Very important for anyone else who wants to go this route - Be aware that there are three or four 944 type condensers available from this eBay store. You will want the one with "Powerflow" in the title. That is the parallel flow condenser. The other ones appear to be the older (R-12 era) tube & fin design. They won't be any more effective with R-134A as the OEM Porsche one is, which is not to say they're no good and won't work well, but it is a fact that the newer style of micro-channel parallel-flow condenser is just more efficient and will yield better results in terms of system efficiency, and will give you lower vent temperatures than a fin & tube design, given the exact same system otherwise. If you want the very best results, go with the parallel flow design. It was/is used by most OEM's for R134A, and now 1234-yf mobile AC systems.
This is the fin & tube model pictured below:

Tube & Fin condenser.png (664.39 KiB) Viewed 677 times

And this is a cutaway view of a parallel flow, micro-channel condenser:

th-2640928716.jpg (23.11 KiB) Viewed 677 times

As a side-note, the micro-channel construction is why most AC shops and technicians will tell you that it's pointless to try to flush one of these. Looking at the picture, it should be pretty obvious why that is so.
If anyone really wants to learn what mobile auto AC is all about, without any BS to filter through, study Tom Lech's Youtube channel vid's .

[Tom]

Great post, thanks Ian. The 944 does pretty well with the old tube and fin condenser. As best I can tell, Porsche kept that old condenser when they switched the late 968's to r134a. That said, the parallel flow condensers produce lower vents temps on r134a for sure -- every bit as low as I ever got with r12. Measured it at 38F just now. I had to get out of the car and take the pic from outside -- too chilly to sit there in shorts. Hopefully, we'll have some more 90F+ days before the summer/fall is over, so I can test it in hotter whether, as the compressor was cycling off when it got down to 38 or less (which I'm hoping means it has cooling capacity to spare in this weather).

temps.gif (512.5 KiB) Viewed 670 times

[Tom]

Well, it was 92F out today and the a/c is still blowing super cold. At the risk of jinxing it, I'd say the eBay Condenser from Cooler Classics is a success!

[samaritrey]

Well, it was 92F out today and the a/c is still blowing super cold. At the risk of jinxing it, I'd say the eBay Condenser from Cooler Classics is a success!

That's good to know that it all worked out with Cooler Classics. I just installed a new Compressor and am only getting it down to 60F so need to recover and try again (got a phone call while I was charging and ended up on the high side of the spec). But was thinking about doing the Parallel flow upgrade while I am at it.

[Tom]

Well, it was 92F out today and the a/c is still blowing super cold. At the risk of jinxing it, I'd say the eBay Condenser from Cooler Classics is a success!

That's good to know that it all worked out with Cooler Classics. I just installed a new Compressor and am only getting it down to 60F so need to recover and try again (got a phone call while I was charging and ended up on the high side of the spec). But was thinking about doing the Parallel flow upgrade while I am at it.

Yes, but for the first one that leaked, and a nagging wonder about the quality of the welds/brazing as a result, the Cooler Classics seems to be a good parallel flow condenser for our cars. (The only plug n' play one available right now actually, at least so far as I could find.) But as I said above, the seller took responsibility no questions asked and replaced it before I could even return the first one, so you should be able to buy with confidence.

60F is not great, even in hot weather with the original condenser. Did it hold vacuum for 10-15 minutes? New receiver drier? I've never over-filled it to the point where the cooling suffers that much, but I understand it's possible. Hopefully, it's just that...