newworld

87s4 aut.

all my fans work correctly, for ac and for coolant temps while car is running.

once i shut off engine, fans should continue to run or cycle like my other porsches.

i got a new intake temp switch, but i still hear the fans while running, and once i shut ignition off, the fan shuts off as well.

i fear heatsoak.

any ideas how to troubleshoot? the new switch is good one, and my understanding is that leads are swappable so i didnt install incorrectly.

if there a relay or other fuse involved?

thanks

69gaugeman

Hmm. On the 90GT they don't always after run. Only when there is excessive heat. With 30 Celsius plus degrees, maybe half the time the after run fans come on.

dr bob

Check to see that the circuit and wiring to the manifold switch will actually run the fans. Run the engine briefly. Secure the hood switch with a small spring clamp or a cable-tie to allow the fan to run. Then connect the two wires at the intake switch. Both fans should run at slow speed. If not you get to go electron-sleuthing.

The fans in my black S4 in Los Angeles have run on in only a handful of very hot cases. Ambient temps approaching 100F, and a hard uphill drive immediately prior to stopping the engine.

I appreciate your concern for keeping the heat-soak time down on the car. On warm days, I pop the hood when I get back up the hill to the garage. So far it's helped keep the under-hood wiring and plumbing from getting crispy. So far the only fault I've had with that system was a switch failure directly attributable to engine wash water on the switch. It lasted a few weeks before it had the fans running all the time.

Chalkboss

My hood switch is bad... does this affect the fan operation? I thought it was just for the under-hood light. My fans turn off when the key is "off" but run when in "acc" position.

SeanR

Yes, the hood switch can cause things to work incorrectly. As the fans are running you should be able to open the hood and the fans stop. If your car always thinks the hood is open, they will stop running with key off.

Chalkboss

Thanks Sean, of course it can't be as simple as a switch for the light.

dr bob

The underhood light is activated by a mercury switch IIRC, and only works when the headlights or parking lights are on. Meanwhile, the hood switch protects your fingers from fan blades, and is also tied to the alarm system in parallel with the radio DIN bucket contact for some reason. Folks replacinga radio and not managing the alarm connection to the radio bucket can inadvertently disable the alarm function and also loose the finger protection.

Leon Speed

Interesting. My fans keep running with the hood open - I need to check if the alarm connection to the radio is intact. I take it it is a "ground" to the bucket, and if there is no bucket a "ground" to the outside of the radio. Or is it part of the DIN connector?

newworld

if the hood switch is bad, i.e. thinking that the hood is open, how to remedy that?

as earlier poster, my fun will run when first position of key start, when i shut off engine it shuts off fans whether hood is open or not.

ill test the wiring jumper to fans, but more than likely i am leaning to hood switch....

i dont mind have the fans run while i am having my hood open as i always disconnect battery when my fingers are near any fan blade.

John Speake

IIRC the thermal switch at the top/back of the intake manifold triggers at 90degC so the engine has to be really heat soaked to trigger it.

newworld

87s4 aut.

john s- we have been in a heat wave in balt 95+F and i my coolant gauge is between the 2 white lines or middle white lines, lets call them upper and lower.

sometimes reaches near upper. i measure 195-197 on upper hose with infrared and 180-185ish on lower hose.

i would have figured the heatsoak fans would trigger after shut down.

John Speake

A quick calc. I make 195degF = 80degC so maybe not quite hot enough, but one would have thought under a closed hood the temp would pass 90degC.....after a few minutes.....

Bill Ball

The height of the hood switch is adjustable. Of course, if it is broken that won't help, but check that the top of the switch is high enough to be compressed by the hood, If not, the bracket that holds it can be adjusted. You can test the switch with an ohm meter for continuity/discontinuity when it is pressed and released before adjusting it.

GregBBRD

I learn something new, every day.

I've never heard the fans run on a 928, after the ignition was shut off....and I always assumed that this did not happen. Now you guys tell me this is a function of the hood switch and something else. Water temp sender? Manifold temp sender?

How hot does it need to be for this to work? I've seen these things "glowing in the dark" and not had the fans stay on.

More info, please.

Dictys

On my S4 the fans would only run on after a hard run in the height of summer, so outside temp in the plus 40c range and the car driven hard. Even then it would only be a couple of minutes at most.

The fans run on depending on the air temp is greater than 87.5c , water temp greater than 87c.

It shuts off when air temp drops below 82.5c and water temp below 83c

(note: my car's normal water temp is between 83c and 86c whatever the situation)