c_span

Been having problems with the factory alarm on my '91 S4 randomly going off - and thanks to all the useful info on this forum, narrowed it down to the bonnet (hood) switch. I have now disconnected this, and so far 24+ hours without the alarm going off! so that's good.

Is it OK to run without the switch (i.e. contacts open) while I source a replacement? Would I be better off jumpering the two contacts (not sure if switch is normally open or normally closed). I understand it controls the light, which is hardly essential, but also a "cooling fan disconnect". That wouldn't affect normal cooling operation with the engine running, would it?

76FJ55

Hood switch is normaly open. with the switch disconnected it just thinks the hood is cloed all the time.

c_span

Ah that's useful - thanks very much!

Randy V

I believe the hood switch also controls the cooling fans, preventing them from coming on with the hood open.

c_span

See above ^^ I was aware of this, but if I understand previous reply then removing the switch entirely won't disrupt the cooling of the engine (it'll just disrupt the safety feature)?

Cosmo Kramer

Mine comes on with the a/c and the hood open I know that for sure.

76FJ55

I should have been a little more description my first post. technically the hood switch is a normally closed switch. When the hood is closed it forces the switch open, so in normal operation hood closed the switch is open. when you disconnect the switch, the system see an open contact and acts as the hood is closed, no light, no alarm trigger signal no fan safety... so if you disconnect the switch don't stick your fingers in the fan with a warm engine.

Alan

The fan safety interlock only affects the fans running after the engine is off. When the engine is running the fans will run as normal (e.g. same as with the hood open). Only when the engine is off and the fans want to run because the intake is hot will this switch stop them. These usually continue to run after you shut the engine off - but its possible they will kick in a little while after the engine was switched off - its designed to avoid them starting up while you have your hands in there. So while it will work fine - be careful...fix it soon...

Porsche assumes they don't need to worry about this when the engine is running since if you stick your hands down near the fan blades then - you are clearly in need of a new brain as well as some new fingers...

Alan

Dean_Fuller

Mine has been broken from the day it followed me home. Will one off a parts car work???

c_span

OK thanks for the info everyone

Nicole

This is kind-of somewhat indirectly related to the topic:

When the hood switch on my 91 S4 malfunctioned, it turned the light back on as soon as it was depressed all the way. Basically, you put the hood down, it turned off, but once you locked the hood, it came back on - which nobody ever noticed.

What I did notice was that my battery went dead regularly within just a few days.

I don't remember how I found the problem. A new switch fixed the issue, and I replaced the buckled (from the heat of the bulb) hood light also. In the meantime I replaced the standard bulb with the LED kind, which protects both battery and the plastic hood light fixture.

c_span

Funny you should mention that, in the other window I was just treating mine to some LED bulbs!

Nicole

Great idea! I am a big fan of LEDs for these lights.

Herman K

However "the lady" that sold me on it at OCIC 09 in Dallas told me I need 6 of them. She deleted 2 (Ops wrong thread)

Tom in Austin

Let's see if my brain is working today ... my light does not come on even with a known good bulb. IF that were because of a bad hood switch, does it follow that my fans cannot run after shutting off the engine?

I have noticed my 928s fans never ran after shutting off the engine this summer, thought it was odd b/c on my 968 they almost ran after shutdown on hot days.