Early car a/c adjustment relay

[P944GUY]

Can anyone lead me to some information regarding the a/c adjustment relay for air conditioning on the early 944 and 924S, it's the black box under the dash near the right hand side of glove box and has an adjustment screw inside it, have been searching my manuals and online but no luck finding anything...my a/c is charged and runs fine but it only cools to a certain point and then cycles off and on , so I think I need to have it get cooler for a longer period of time before it cycles..my mechanic told me about the relay and may just need to adjust the screw, but can't find anything regarding which way to adjust it or any specs of adjustment..thanks, Jeff

[mattdavis11]

There is absolutely no need to mess with it unless someone fuched with it after it left the factory.

I don't recall seeing an adjustment screw on mine, and I have had to repair a burnt trace inside the box of which you are concerned.

That box is the a/c amplifier.

What refrigerant is in the car? How much oil? What is the ambient and high/low pressure?

[P944GUY]

I just made an amazing discovery...and keep in mind I live in Phoenix, where it's effing hot in the summer..today is 100 degrees...anyways back to the a/c amplifier relay..My a/c system running completely normal, as everything in it is new..I would switch on the a/c and it would cool down to 38 degrees but then would cycle off til it go to 58 degrees and then cycle back on again and cool to 38..measured with a thermometer in the vent..So my discovery is that if you turn the adjusting screw adjusts the temperature swing 38-58 degrees which it was originally set, I turned it down towards the colder arrow- yes it's marked , and now have ice cold air with a temperature swing of 38-43, meaning it cools down to 38, cycles off til it gets to 43 and cycles back on again to cool down to 38 again....Ice Cold !!!!!! So for those of you with an early car and you think your air conditioner sucks , although runs cool and then seems to get warm then cold, adjust the screw on the a/c amplifier relay towards cooler arrow and you will get a smaller temperature swing, thus keeping a more constant cooler temp in your car...and we all know that the early cars ventilation system is just plain sucky anyways...Now, granted I live in Phoenix where it's just hot and the sun beating in thru the windshield heats the car up very fast, this adjustment was a life saver, depending on where you live you may not need such a drastic change in temperature swing..just unscrew the pass side kick panel, unbolt the a/c amplifier.."black box", turn it so you can see the hole with a thin piece of film on it , get a small screwdriver, pierce the film, start the car, turn on a/c, put a temp gauge- long one like a cooks temperature probe in to the vent, your going to be listening for you compressor to be cycling off and on and making note of the temps on the temp probe, you can now adjust the screw on the box towards cooler arrow, which is to the left, mine I turned about 3/4 turn left...also your watching the temperature gauge fluctuation in temp as the compressor cycle on and off, mine was initially, on til 40 degrees, then off til 58 degrees then back on til 40 , now I set to cool to 38 , off to 43 and back on again...my mechanic said a 5-6 degree swing was very acceptable , and also since I was in the shade the temps moved very quick, now out into the sun and some real hot temps see how it performs.......

[mattdavis11]

Interesting. Mine cycles off at 28 and comes back on at 40ish. Never been messed with. It's now R134a.

[John_AZ]

Bookmarked!
Nice find Jeff.

I will have to check the position of my "black box" on each 924S.
Like Matt, I converted the '87 to R134a and still have R12 in the '88.
I gave the '87 924S and the Jeep a top off of R134a (same can) just before the first 102* Phoenix temp yesterday-just the beginning.

John

[Butters944]

Figured this thread is perfect timing for my current early AC problems, so I had to finally make myself a Pelican account.

My father and I are totally confused. We've overhauled the whole system and finally thought we had it working perfect, but we're NOT QUITE there! When the car is stopped, it blows super cold. This thread led me to adjust my black box down a little bit (assuming the change to R134 affects that box's calibration). It cycles between as low as 28* up to 40*, which is awesome. Once I get to speed it doesn't blow as cold, gets all the way up to 70. I've confirmed it has nothing to do with engine speed, only vehicle speed. We tested our temps right at the outlet of the AC box, so it has nothing to do with the heater or vent systems. I've also blocked off my heater inlet in the engine bay with duck tape because I thought it might be getting in through there.

Any ideas? It doesn't make sense because naturally an AC system should blow COLDER at speed.

How could my system work SO good at idle (regardless of RPMs), yet warm up at speed..?

[John_AZ]

Hi Butters,

My first suggestion would be the condenser is clogged with oil or dirty.
Cleaning externally may help by soaping and rinsing from the engine side to the front. This avoids the bugs from getting further into the fins of the condenser and radiator. Internal cleaning involves removing freon and back flushing the condenser.

There are new parallel core condensers available from Griffiths and I think V2Rocket builds one as well.

Porsche 944 air conditioning parts, Behr, Bosch, Nippondenso, Kuehl, Seltec, Sanden, seal, convert, conversion, barrier hose, Porsche compressor, Porsche condensor, condenser, receiver drier, evaporator, expansion valve, upgrade, R134a,R12,924,951,96

Since you have experience and assistance with the AC, your line pressures have been checked. But they may still not be accurate.

This may help, credit to AllExperts:



Matt and Griffiths are the AC pros on Pelican.

GL & welcome to Pelican.
J_AZ