Blower resister

[sandiego]

1. I measured the resistence of my "Blower Resister module" and at room temp and it reads zero ohms. Visual inspection shows both a resister and a set of contacts in parallel. The factory schematic doesnt show the set of contacts. Is this possibly a bimetallic switch which opens at higher temps allowing the resister to come into play? (When I put a hairdryer to mine it didnt open.)

2. What is the value of this resister. (Mine measures 55K ohms but one schematic I saw showed 0.35 ohms.)

[kenhill]

Are you referring to the resistor that you use to replace the blower in a 964 if installing a bypass tube?
If so I am interested in what you find out because I am unable to get heat after replacing the blower with the bypass tube.

[sandiego]

Yes. This is the Resister located in the bypass tube. It is used to lower the voltage to the blower to obtain slow speed operation.

[sandiego]

Found this from "kenhill": The slow speed resistor is the thing with the spade connectors. The other "probe" thing is a temp sensor.

There was a recent thread on the rennlist.com forum that described what was needed to get the HVAC to work correctly without the fan and sensor in place. It involved connecting a 50 ohm/15 watt resitor in place of the fan motor so that the HVAC controller thought the fan was running.

-doug

[Don Plumley]

Here's a very descriptive DIY.

I've done this in my 993 and everything works just fine.

[kenhill]

Originally Posted by montereyboy

Found this from "kenhill": The slow speed resistor is the thing with the spade connectors. The other "probe" thing is a temp sensor.

There was a recent thread on the rennlist.com forum that described what was needed to get the HVAC to work correctly without the fan and sensor in place. It involved connecting a 50 ohm/15 watt resitor in place of the fan motor so that the HVAC controller thought the fan was running.

-doug

My car was built in November '90 and though I have done everything suggested on http://www.porsche964.co.uk/technical/noheater.htm
I am only getting cold air when on the blue dot. I have not been able to get the system give any heat and when switched to heat it simply turns off.

[Hamptonsam]

The resistor method does not work on the early models. I think the CCU changed sometime in 1991. I was going to try to resistor just to see, however I have not heard of anyone getting it to work with the early models.