Adamant1971

No affiliation, just a PSA. For those who wish to keep their car's HVAC brain stock.

https://www.ebay.ca/itm/Gruner-202-R...f67e%7Ciid%3A1

SeanR

They've been up for a long time at $120US. This person isn't taking Paypal it looks like. E-mail money transfer only.

Mrmerlin

FWIW they are making new relays that are 5amp thats what you should be installing

GregBBRD

^^^^^This.^^^^^ As the compressor magnet coil winding ages, the current draw goes up and the 2.5 amp relay struggles.

It was actually marginal, when they made it...they should have known things are going to "age".
And a company that hangs their hat on being an engineering firm, should have been smart enough to put a fuse in the circuit to protect the traces on the circuit board in the HVAC control unit.

Not their finest moment....

Adamant1971

Overcharging the AC is also a major culprit of increased current draw, not just compressor age. I agree they should have had a fuse in this system.

We can come back to this thread in another 20 plus years (Unless Corona takes us all out) and I will report if mine has failed again. Consider my car an experiment. LOL

GregBBRD

Think about this, a bit.
The coil for the magnet is not affected by the load on the compressor/clutch. Overcharging can be hell on the clutch, but the current flow through the magnet doesn't change.

The Forgotten On

I still find it dumb that Porsche had a relay on the fuse panel just for the AC compressor clutch in 78-79 and then decided that was excessive and instead made it a small relay inside of the head unit.

Definitely not one of their finest moments.

I would replace it with the 5 amp relay and then install another relay inline with a fuse (also add one at the freeze switch for the head unit relay) to take load off of the head unit traces in case of a voltage drop.

This way you wont have as much of a risk of burning up the traces in the head unit. 3 amps or a few milliamps, which one do you want put through a 2 amp relay?

Adamant1971

Makes sense. So far this replacement relay has been fine, almost 2 years now. I have an extra head unit on the shelf just in case.