main heater blower stays on all the time

porschenut · 01-05-2007, 04:21 PM

I recently had some electrical issues that I believe were caused by a faulty voltage regulator. The alternator/VR, headlight switch, alternator warning light bulb, and a couple of shorted wires were fixed/replaced. I still have one lingering issue though...the engine compartment heater blower stays on in any key position except "off". I suspected a faulty blower relay but I swapped mine with a known good one and it didn't fix it. The car is an '86 with automatic heating, and the heater control and footwell blowers all seem to be working normally. Any ideas why the main blower runs all the time?

strupgolf · 01-05-2007, 05:12 PM

Mine does the same thing after some electrical work. 86 Targa, auto heat. I've searched but all I could find were guys whose blower didnt work, not one that worked all the time. Anyone ?

sus911 · sus911's Garage

Don't these run even with ignition off when a hot engine condition is detected?
Which leads me to suspect the cyl. head temp. sensor.

Mysterytrain · 01-06-2007, 04:13 AM

I was thinking the same sensor that SUS911 mentioned. If the sensor has failed and thinks the engine temperature is at its high set point it will turn the blower on if the car is not moving. I'm betting the blower stops turning once you are under way. The sensor acts like a switch its either open or closed...I'm not sure which is it's normal state maybe someone with a Carrera can ck it out.

strupgolf · 01-06-2007, 05:09 AM

My blower keeps blowing at speed also. My cabin gets pretty warm with the auto-heat dial on 0. Well, wait a minute. It could be my footwell blower motors running that I'm hearing. When I move the dial up to 7 or 8, I can hear more blowing in the cabin, which was the case before. But last year, when I dialed 0, it did'nt. The engine temp sensor could be the culprit.

porschenut · 01-06-2007, 06:19 AM

Quote:

Originally posted by sus911
Don't these run even with ignition off when a hot engine condition is detected?
Which leads me to suspect the cyl. head temp. sensor.

There's an interesting theory. But it wouldn't run with the key in the off position, i.e. straight up and down, would it? Mine starts running as soon as I turn the key to the ON position, one clockwise click.

dfink · 01-06-2007, 07:59 AM

Seems to me that the fan will run even with the switch turned off if the engine is hot enough. The switch has to on for it to run with the heater controls. These are some of the isssues I was hopeing would be answered in the attached thread. The engine off fan running should be easy enough to test but I don't currently have an engine in the car. But what sensor is it that is monitored for the this condition to be true. The only heat sensor I know of is the cylinder head temp sensor and that is I believe an analog sensor so at what point would it trigger the controller to turn on the heater.
The heater circuit does have power with the switch off. And if this is what is keeping the heater motor on all the time then why isn't the temp gauge reading really high.
If heater only comes on when switch is turned on and heater controls are turned off then maybe a short to ground someplace as all the heater control does is ground the circuit to tell the controller to turn things on.
I get so confused.

Heater Circuit Again

dfink · 01-06-2007, 02:03 PM

OK so I am wrong there is another temp sensor in the air breather. I assume anyway that is a temp sensor.

Falk930 · 01-20-2007, 01:00 AM

UUps,
so much info in this forum about the heating system!

Difficult to understand all, as english is only my sec. language.

On my 930, as far I know, no rear fan,
the foot fans run all time.

Currently the fuses at the fans are blown, when I put new ones in there, they run in ALL positions :-)

Any ide ?

*and I totally agree on this crap of engeneers work
with a highly complicated heating system,
which in most cases provide problems.

greeting from germany

Falk