Stan944

I recently installed a new coolant temperature switch (in addition to the new thermostat). The problem is that after a few minutes of driving the cooling fan gets on, and never goes off, until I turn off the engine (it goes off with a few minutes delay).
The thermostat I installed is rated for lower temperature (90C/85C instead of 92C/87C for the original). I think the problem is now that the engine generates so much heat that the cooling fun doesn't have enough "juice" to cool it below 85C. I don't think lowering the engine temp by 2C harms the engine, but will probably cause premature wear of the fun and possibly the alternator.
I guess I need to get the proper temperature switch... I hate it when I mail order parts, and a "close" replacement arrives without warning. What do you guys think?
Stan

led

I just installed a Thermoswitch as well and the fans don't turn off until a few minutes after I turn off the car. My temp switch turns the fans on low speed at about 85ºC so unless the temp of the coolant goes below that, the fans won't turn off. What I think happens is that the fans will change speeds according to the coolant temperature, constantly going from low to high and back.

gleamingred944

On mine, when the engine is hot, the fan runs high when ignition is on, otherwise low until temperature drops. The low is so quiet I didn't hear it when the thermoswitch stuck on once, and it drained the battery after a couple of days. Mine is an 86 na - I gather different years used different systems. If the fan comes on when the engine is cold, you definitely have a bad thermoswitch, or a short in the wiring.

Stan944

thanks for the replies,
gleamingred944: I put the new thermostat because it got stuck in the ON position a few times and drained the battery. My fun does NOT come ON on cold engine, it just doesnt go OFF when I think it should while I keep driving!
General question : I wonder how often the fan goes on/off in typical city-driving conditions for 944 (1983)?
stan

led

I think the earlier cars had an on/off thermoswitch, the late models have a off/high/low, actually I think it would be off/on/on but the specific application would be for low and high fan speeds. The fans will not come on while the engine is cold but will do so when it reaches aprox. 92ºC and will turn off when at or below 85ºC (according to manual)

Dales944

"Cooling Fun?"

led

yeah, it's fun to be cool ain't it?

Stan944

Thanks Dales944, I corrected the spelling...
I can only say that English is not my first language, and sometimes my spelling goes funny.
Stan

Dales944

Stan - I have complete respect for anyone who can communicate in a second language as good as yourself. I just thought it was funny because you repeatedly used the word "fun" instead of fan. If you had spelled "fen" or "fon," etc., I wouldn't even have commented (typos happen all the time). Thanks for taking it in the good humor that I intended, and of course - good luck with your "fun" problem.

Quote - "I wonder how often the fan goes on/off in typical city-driving conditions for 944 (1983)?" If it helps - my '83 fans will kick on as soon as the guage reaches the half-way mark. I installed a low-temp switch last summer (mine would only come on with the A/C prior to that). In the local 55/60 Deg F, they come on about every 8 to 10 minutes (city driving).

Stan944

Dales944: I admit, it was funny.
Stan

Jeff928S4

Stan........you're French????

944S Boyeee

Bri Bro

There are three sensors that go to the "Coolant Fan Relay". The "Coolant Temp. switch" (what is called fan switch on the Radiator) has two internal temp sensors(three terminals are on the back of the switch). One closes at 92C (terminals 2 to 3) and the other closes at 102C (terminals 1 to 3). The other sensor connecting to the Coolant fan relay is the "Refrigerant Temp. switch" and is set to close at 52C. The refrig temp switch is connected in parallel to the 102C coolant temp switch so if either of these switches exceed their limits the fan motors turn on high. The AC relay is also connected to the Coolant fan relay and turns on the fan when the AC is switched on.
The coolant fan relay also has two connections to 0.9 Ohm resistors. When the fan motor is running at "low" speed, the voltage to the fan motor goes through the 0.9 ohm resistor, reducing the speed of the motor. When the fan motors is in high speed, a relay is shorted across the resistor which causes the fan motor to run at high speed.

So there are six things to check when the fans will not work correctly. The fuse, the wiring, the sensors, the motors, the resistors and the Coolant fan relay. If you pull off the Coolant Temp. switch plug and short terminals 2 to 3 the fans should run at low speed. If you short terminal 1 to 3 the fans should run at high speed. If you turn on the AC (AC is charged and in working order) this will also turn on the fan motor.

led

His car is an 83, early 944's have a on/off temp switch. Only two terminals on it.

keith

Are you certan you've bled the cooling system entirely?

Stan944

As led pointed out, the temp. switch on the radiator has only 2 terminals on my 944(1983).

I'm not saying all the related components are in perfect condition, but:
I'm comparing the behavior before and after the last repair: I installed the temp. switch, which is NOT exactly according to the specs (90C/85C instead of 92C/87C for the original, i.e. the switching temps are 2 deg C lower now!).
I put the new switch because I noticed that occasionally the radiator fan kept spinning at low revs for hours after removing the key from the ignition.

I would like to know if the new problem, see below, which didn't show like this before(!), is caused by the reduced switching temperatures of the new temperature switch!
Reminder:
Although the cooling fan gets ON after a few minutes of driving, it never goes off, unless I turn off the engine (then the fan runs at low speed for a few minutes, and eventually goes off).

Keith - I put almost exactly as much new coolant (including adding some on the next day), as I drained out. And I kept the bleeding hole open.

944S Boyeee - I'm Polish, but I've been in Canada for the last few years.

cheers, Stan