Mongo

I noticed my car's temperature has been high lately. It runs usually around 3/4's. Today on the way to work, the temperature went down only for a little bit, but was still above 1/2. When I pulled into work, I made the following notes:

-car's fans only run when A/C is on and fan blower speed is set to max.

-when the car was shut off, no A/C on, the fans were operating.

- I did not hear the fans come on any time prior to that, but the temperature gauge was still pegged at 3/4.

Does this sound right? I just had the radiator flushed and my water pump doesn't even have 10,000 miles on it. Could this be a faulty reading on my temperature gauge?

87 S4 car by the way... Thanks.

danglerb

Sensor in the radiator or wiring to it? Cheap to swap I think.

Mongo

being a veteran in fan diagnosis on 944s, the 928 completely boggles my mind. More mysterious than women!

If the fans were operating in those certain situations, I don't think it could be the fan switch. If the fan switch (or sensor) had failed, the fans would stay on all the time. I could be wrong

danglerb

Fans turn on with the AC, but not from heat, sounds like sensor to me, and they are what $10 and a common part I think. OTOH relay relay relay, right? I don't know how the 87 fan controller is wired up. Kinda surprised nobody smart has jumped in.

Mongo

The fan switch is $10? Nooo way!

danglerb

Gee, maybe I should have bought that last one on ebay. $24 at Rockauto.com

1987 PORSCHE 928 S4 5.0L 4950cc V8 FI (B) : Cooling System : Coolant Temperature Sensor Print Save My Place
Item Price Core Total Advice
STANDARD MOTOR PRODUCTS Part # TX39 More Info
$23.79 $0.00 $23.79
Add to Cart
OEM Part # 92860620101 More Info {Coolant Temperature Sensor}
$41.79 $0.00 $41.79
Add to Cart
AIRTEX Part # 5S1563 More Info
**Non-stock item--shipping delayed up to 2 business days**
$38.89 $0.00 $38.89
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danglerb

Its the switch sensor for my 83 thats $10, want to trade?

Mongo

Got an update. This looks like an intermittent problem. The cooling fans come on at 1/2 temporarily when the engine is under load. The intake temperatures were obviously hot.

I jiggled the connectors this morning and checked to connection on the fan switch on the radiator. The harness is old and cracked but the wires are still good. After jiggling the Temp II sensor on the intake manifold, the fans came on normally...or 1/2 like I stated above. Bad Temp II sensor????

dr bob

Temp-II doesn't have anything to do with the fan operation. What else did you jiggle?

Basic fan speed control is based on temp reading from sender at the bottom-front-left side (car-left is driver side on US cars...) of the radiator, under the AC condenser on your car. It's a reverse-coefficient thermistor-type sensor, not a switch as the WSM electrical diagram description might lead you to believe.

Fans also run on high intake temp (switch on top of intake manifold closes) and on high auto trans fluid temp, determined at a switch near the torque converter someplace. Intake and trans temp modes are not sensitive to ignition switch position but the radiator temp operation is only with ignition switch in run position.

Mongo

Hey Dr. if you're still on, sorry for the misconception! I thought the temp II sensor was on top of the manifold. I goofed! That was the one that I jiggled.


I also read somewhere in a post you put up, that I contact the 2 connectors on top of the intake manifold to that temperature sensor to turn the fans on...is this correct?

Mongo

bump

dr bob

Sorry for my local distraction - work!

Yes-- there's some discussion on the safety switch function of the hood switch, so you may need to tie-wrap the hodd switch down while you test. My '89 doesn't need that, fans work with the hood open.

Mongo

My '87's fans also work with the hood open. I thought the whole safety thing was BS?