Cooling Fans Not Coming On 86 Porsche 944

Old 04-30-2019, 01:26 PM
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Default Cooling Fans Not Coming On 86 Porsche 944

Hi all -

Since my previous post on April 4th, I have replaced the thermostat (even tested it in boiling water before installing just in case), lower & upper radiator hoses, hose from expansion tank that goes across top of radiator toward passenger side of radiator and expansion tank cap. Also replaced thermofan (cooling fan) switch and the cooling fan relay (ouch over $100). I performed the Clark's garage test and jumpered the the cooling fan switch and both fans came on so i though the cooling fan relay must be bad (this is after i have replaced the thermofan switch. I got the cooling fan relay in yesterday put it in thinking my overheating/non working fans problem would be over. Well, it did not solve it. The fans will come on now but only when I turn the A/C on, but they shut off as soon as i turn the A/C off. I tried multiple times yesterday of the letting the car warm up and each time the temp gauge goes all the way up to the 3rd white mark and continues to rise so i shut it off. I have also felt the lower and upper radiator hoses after letting it run and they both get hot. Replaced both cooling fan fuses as well although both tested good.
When my son and I installed the thermostat we found an 82C one i think the original was an 80C...and the thermofan switch i think was 90C to...can't remember upper limit at the moment.

Is it possible I still have air in the coolant system and this is causing no signal from thermo fan switch to cooling fan relay to make the fans turn on once the car warms up to temp?

Or are there other possibilities that I am overlooking?

Looking through the threads I saw lots of different issues on fans not working, thermostats, bleeding the coolant system. But I did not see anything posted that air in the system would cause the cooling fans not to come car is equipped with two cooling fans but it is non-turbo. 86 NA 5 speed

The issue is driving me crazy to try and resolve.
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Old 04-30-2019, 05:52 PM
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Old 05-04-2019, 02:15 AM
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Originally Posted by Bowhunter1974 View Post
The fans will come on now but only when I turn the A/C on, but they shut off as soon as i turn the A/C off.
Take a look at the connections and the wiring going to the two 50mm diameter ceramic fan resistors.

On the early cars, they were mounted in the engine compartment, under the plastic shroud, near the battery. On later cars, and my '86, they were mounted [on a bracket] inside the cabin, to the firewall, behind the glovebox. My suspicion...your connectors and wiring have seen better days.
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Old 05-07-2019, 10:48 AM
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Thanks to 931 guru and mel_t_vin - the cooling fans finally engaged but not until between the last 3rd white mark and the orange hot line so well over 100 C - I did replace the cooling fan switch with a lower degree setting (83 to 95 C) - tested it out yesterday and the fans kicked on right at 100 C (last white gauge mark) this time. Fans did not come on at low speed but high speed, when I shut the car of they ran for a few minutes in what I think was low speed.

It seems i may need to take the dash apart to get to the resistors behind the glove box. I was hoping they were under the plastic shield below the windshield under the hood. I suppose it is possible that they could be corroded not causing fans to kick on at low speed when they should. It is odd when shutting the car off they seemed to be engaged in low speed as well as when i turn the A/C on they run in a lower speed.
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