Cooling fan
- Thread starter Guest
- Start date
Interesting ... the thermotime switch (as it was called) on VW's was a small wax canister alongside a pari of terminals. As it got hot, the wax expanded and pushed the terminals together. Usual failure mode was that the canister would spring a leak and the wax would trickle out of it, and it would then not close the terminals.
Sounds like the Porsche switch is different.
Oli.
berg944
New member
Xenon,
My understanding of the circuit is slightly different.
IIRC the thermo switch operates one fan at 92'c and both fans at 102'c
the slow speed is only with ignition off (so as not to drain the battery) and has a different circuit with a resistor, It still uses the 92'c part of the thermo switch.
This is part of the reason why the fan stays on even with the ignition off when the thermo switch fails.
Mike[:'(]
My understanding of the circuit is slightly different.
IIRC the thermo switch operates one fan at 92'c and both fans at 102'c
the slow speed is only with ignition off (so as not to drain the battery) and has a different circuit with a resistor, It still uses the 92'c part of the thermo switch.
This is part of the reason why the fan stays on even with the ignition off when the thermo switch fails.
Mike[:'(]
xenon
New member
Hi Mike
Is that not on earlier cars?
Put it this way, I tested the new thermoswitch last night with a pan of boiling water and it works as follows: At 92oC (or thereabouts) pins 2-3 close. Once the water was boiling furiously pins 1-3 close.
On my car it would work thus (manually jumpering the connection to replicate):
Ignition on:
Is that not on earlier cars?
Put it this way, I tested the new thermoswitch last night with a pan of boiling water and it works as follows: At 92oC (or thereabouts) pins 2-3 close. Once the water was boiling furiously pins 1-3 close.
On my car it would work thus (manually jumpering the connection to replicate):
Ignition on:
- 92oC, pins 2-3 close, both fans slow
- 102oC pins 1-3 close, both fans fast
- 92oC, pins 2-3 close, both fans slow
- 102oC, pins 1-3 will close, but fans only run slow as ignition off.
xenon
New member
OK, drained and flushed the cooling system today, and fitted a new thermoswitch. Now it all works as it should. Let the engine warm up and the fans cut in on slow at 92oC and on fast sometime after. Switch off the ignition and the fans continue to run on slow until <92oC.
Sorted. [
]
Sorted. [
]
peanut
Active member
I have a 89 S2 which originally had A/C removed by previous owner. Mine has two fans which switch off with the ignition too. They shouldn't, so the wiring must be wrong through the redundant A/C somewhere .
This Saturday I came back from shopping and the car was a little hot and fans running so I left the ignition on aux with the fans running meaning to come back in 10 mins to turn off.
This morning I go to the car and find .... you guessed it the keys still in the ignition and a flat battery. *%$£*
Took me half an hour to get the boot open and a further hour to charge the battery enough to start. Nightmare.
I am sure on my old 86 Lux the fan used to stay on after the ignition was off as it should . I'm going to look at the wiring this w/e and see if I can find a way to rewire it so the fans are on with ignition off. I already have a new sender. Just hope I can get the old one out . If not it might be easier to drill and tap a new hole and use a helicoil if nec .
This Saturday I came back from shopping and the car was a little hot and fans running so I left the ignition on aux with the fans running meaning to come back in 10 mins to turn off.
This morning I go to the car and find .... you guessed it the keys still in the ignition and a flat battery. *%$£*
Took me half an hour to get the boot open and a further hour to charge the battery enough to start. Nightmare.
I am sure on my old 86 Lux the fan used to stay on after the ignition was off as it should . I'm going to look at the wiring this w/e and see if I can find a way to rewire it so the fans are on with ignition off. I already have a new sender. Just hope I can get the old one out . If not it might be easier to drill and tap a new hole and use a helicoil if nec .
peanut
Active member
ORIGINAL: xenon
OK, drained and flushed the cooling system today, and fitted a new thermoswitch. Now it all works as it should. Let the engine warm up and the fans cut in on slow at 92oC and on fast sometime after. Switch off the ignition and the fans continue to run on slow until <92oC.
Sorted. [
Nice one well done! I'll try fit my new switch this w/e .
xenon
New member
@ Peanut - You just need to fix the sender - the wiring is much the same other than the slow speed relays are energised if the A/C and ignition is on. The sender on mine came out very easily and I didn't have to remove the fan cowling(s). You need a deep 1 - 1/8" socket (or 29mm) plus an extension bar. Some radiators have a plastic thread and some brass, I'm told. Mine was brass but the sender came out no problem at all.
Getting the front undertray off (to access radiator drain plug) was the b&stard - the self-tappers were seized. If only they'd spent a few more pence and used stainless fixings []
Getting the front undertray off (to access radiator drain plug) was the b&stard - the self-tappers were seized. If only they'd spent a few more pence and used stainless fixings [
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