roman944

ordered: A/C fan relay, low temp thermostat, low temp switch

I can reconnect some of the wires for the A/C and see if it will work

my dad mentioned that it's possible to run the car w/o a thermostat

wouldn't it be easier just to run a switch for the fans?

roman944

& what do you mean by resistor? the fan switch?

smokin_944

Way back on an earlier post I explained that in order for the driver side fan to run at slow speed it was connected to a resistor, a round hockey puck looking thing that is tan in color. If the resistor is bad or the connections are corroded, the driver side fan WILL NOT RUN at slow speed. The slow speed on the driver side should start running at 75 degrees C (give or take 2 or 3 degrees). If this is the case (bad resistor), there is nothing wrong with your 75/70 thermoswitch. Find the resistor and check the connections.
2) Most if not all of the Porsche 944 gurus DO NOT recommend running the car without a thermostat. The cooling system is not designed to run that way.

roman944

do you happen to know where this resistor is located? I did a search and found where they are on late cars, but not early cars

seems like a logical thing to check next, everything else is new already!

NYFlapjack2

I was all over this in my car a year ago as it all was strange acting to me...My car -1983, with AC. From the wiring diagram (Clarks) is looks OK to how my car acts... when the Rad Temp switch completes at the high temp point, it completes ground of fan relay and that pulls both fans on then...

Mine Low speed fan LH side will only come on when car key is off and yet the rad is hot past the fan switch set point. To me it is kind of a engine heat soak while parked helper is all...I don't see a low speed fan running anytime the engine is running in my car, nor do I see how wiring supports that....regardless of temperature...(early cars).

I tested as: With key off...jump the rad fan switch 2 wires together (you have a 2 wire fan switch right?) and low speed should run LH fan only. if you get low speed believe you proved resistor is OK.

Turn key on and ac switch off, while 2 rad fan switch wires jumped together and both fans should run on high. Fan relay working proved.

Then 2 wires of that rad fan switch off not touching anything and key on AC switch on and both fans should run on high (engine running or not regardless of its temp, just key on). (proving out AC relay working, pulling in fan relay too)

More babble:
The Resistor is I believe is behind our speedo cluster it bypasses the fan relay sending a lower voltage to power the 1 fan Low when the temp switch is still grounding (so rad is still hot,& key off).

The 2 numbers on a Rad Fan Temp switch I believe refer to the (high#) temp setting it gets to to make circuit closed and then the low (#) set point it disconnects switch...I boiled mine with a candy thermometer checking past year playing and saw that...

Remember the fan switch is your rad temp. Your gage in the dash is coolant at the sender in your engine head it seems normal to be hotter and to climb with little or no air flow before the fans kick in....

Running my car in driveway watching the cycles - My cooling fans do not turn on at all until the head temp gage is up to the 3rd hash or more ...then you can watch the gage drop as the fans work on high...until few minutes later the fans stop, temp gage is back centered. Keeping it running sitting there it runs ...it works up the temp and the cycle repeats

On the road my temp gage is rock centered, until long traffic lights.

roman944

your thread was one of the ones that showed up in search

sounds similar to mine, except that I don't get the low-speed fan on

and turning A/C on does nothing - once I have the new relay, we'll try again with a new relay, maybe that 1 worn pad inside it is why the fans don't turn on with the A/C ****, but turn on when the thermostat kicks in?

roman944

my a/c hasn't been working even before we took everything out, maybe it was due to a bad relay, so maybe when I get this new one, I'll put it in and see if the fans will turn on with the A/C ****, if they do, I won't even worry about everything else

and if they don't, looks like fan resistor is located behind the speedometer on the early cars? I may try that

harrisonrick

IIRC the resistors in an early car are located in the passenger footwell...there are 2 greyish/clay coloured ones. Quite often the wires are green/corroded/off.

In a later car they are under the hood, under the plastic cover that covers the defroster fan.

smokin_944

Hi Rick, the early cars only have one resistor cause the cooling system is designed differently than the 85.5+ cars. On the early cars, only the driver side fan goes on at slow speed. When the car is shut off, only the slow speed circuit remains functionnal, meaning only the driver side fan runs, at slow speed.
NYFlapjack2, as far as the low speed fan not going with the car running, well... the resistor is in parallel with the DC source going to the fan right from Porsche so... try this... run the car til the primary fan comes on. Throttle up and down til the second fan comes on, cause it only runs at high speed. At that point both fans run at high speed, then you'll see the difference. Porsche did that so the 2 fans wouldn't kill the battery.

roman944

there's nothing in the footwell on passenger's or driver's side

I'm going to wait for a new A/C relay to see if I can get both fans to go on from get-go, if so, I won't worry about all the other stuff

smokin_944

If you even bothered to read Clark's garage you would understand there aren't 2 resistors on an early car. There just aren't. Read what it says and TRY TO learn!!!!!

roman944

drove the car on the road today, temp stays at around 3rd mark, then fans come on, temperature appears to be between 3rd and "hot"

so I still have issues that need to be solved

MichaelK

that is where mine hangs out. I have some other electrical problem though which causes the needles to dance around a bit so I am wary of their position being accurate. I figure (perhaps incorrectly) that if they hang out at the same spot consistently then I am probably ok.

roman944

well, when we first stated driving it, it was fine and it seemed to climb up in a smooth way, like it didn't shoot up after a couple of seconds

we were @ a highway speed until we stopped, then the temperature started creeping a little past the 3rd mark, then we went back on the highway, and temperature stayed @ the 3rd mark, once we stopped @ the exit light - it went PAST the 3rd mark, just a hair away from the "HOT" zone"

but it seemed to lower back down to 3rd mark once we started driving again

looking at this, there is probably more air in the system? going to go at it again today after work

I was also thinking, that maybe we have a bad mix of antifreeze? they do have this tester that sucks some of it up and tells you how strong of a mix you have ...

our plan at this point was to wait until all my low-temp goodies come in, drain the system, swap new low-temp goodies in, and fill the system again

only thing is, how do I completely drain everything? or I won't have to? certain coolants are OK to mix, we were using Prestone 50/50 form Autozone, but we did top it off with water/antifreeze mix

harrisonrick

Damn Smokin...you're right. The resistor is behind the tachometer on an early (yes, only 1 )...forgot how long its been since I've crawled around in an early car.

Frig...I'm rusty!