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blackhat · Posted: Thu Apr 24, 2008 8:31 am Post subject: Help with temp sensor/fan wiring

Hey all!

Well, it hasn't even been a full day since I've actually had my first Porsche and I've got a problem. It's with the radiator system. I finally got it home and noticed radiator fluid squirting out from the resovoir.

So, I ran over to AutoZone and picked up a new radiator cap and thermostat. As soon as it stops raining, I'll go out and pop those in.

When I was driving, I noticed that the temp gauge in the dash was pegged. It was pegged if it had just started or had been running for quite some time. I figured it was just electrical. Sure enough it was! While I was underneath the hood, I noticed that the people before me pulled the wires off the the sensor on the top of the radiator and put them together.

I think I want to put them back where they were right? I mean, the fans aren't running at all either and it seems that they are part of the this system.

Anyways, does anyone have the color codes for the wires so I know what goes where? There's only two. If it doesn't matter if I do trial and error, please let me know. I just don't wanna blow something up right away.

Thanks in advance!

EDIT
------
Before I get flamed, I did look at the FAQ about the fans. I'm curious though as to what color is hot and what color is ground. I also think I found a break in a wire so I'll splice that back up.
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My First Porsche
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1978 Porsche 924 N/A

Paul · Posted: Thu Apr 24, 2008 9:07 am Post subject:

The sensor on the radiator is for the radiator fans. When the wires are connected together, the fans should run all the time.

You will need to reconnect the 2 wires to the sensor, it does not matter which wire is on which terminal.

Your overheating problem was caused by the fans not running.

You will need to fix the fans, refill the system, and bleed it.

Brown is ground. In this case the sensor is nothing more than a temperature operated on/off switch. All it does is to provide a ground to the fan relay coil (the other ends of the wires: one goes to ground, the other to the fan relay coil).
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

blackhat · Posted: Thu Apr 24, 2008 11:05 am Post subject:

Perfect! I'll run out and give that whirl.

I found out why the fans weren't running all the time since the sensor was tied together. Some how, the hot wire for the fans was broke so I spliced it back together and now one of the fans runs. Odd, but it's better than none of them.

I'm glad you said something about the wires and that sensor 'cause I really don't feel like unhooking the battery when I park the car.

I just got done fixing that lead wire I was talking about, and swapped out the thermostat and radiator cap so hopefully all should be good now.

Thanks for the quick response!
_________________
My First Porsche
-----------------
1978 Porsche 924 N/A

Paul · Posted: Thu Apr 24, 2008 11:14 am Post subject:

Make sure you bleed the cooling system before driving the car.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

blackhat · Posted: Thu Apr 24, 2008 1:08 pm Post subject:

Paul · Posted: Thu Apr 24, 2008 1:16 pm Post subject:

It's on the thermostat housing or the hose attached to it.

With a cold motor, remove the bleeder and fill the coolant tank to slightly above max.

Firmly tighten the coolant tank cap.

Safely place a towel around the thermostat housing.

Start the car and block the idle at about 1200 - 1500 rpms.

When coolant only flows from the bleeder, replace the bleeder with the motor still running.

Let the car run until the radiator fan kicks on, then off.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

blackhat · Posted: Thu Apr 24, 2008 1:19 pm Post subject:

I didn't see anything on the housing but there is a red knob on the hose leading to the thermostat housing. Could that be it?
_________________
My First Porsche
-----------------
1978 Porsche 924 N/A

Paul · Posted: Thu Apr 24, 2008 1:22 pm Post subject:

Yes that's it, I was adding that to my reply as you were posting....
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

blackhat · Posted: Thu Apr 24, 2008 1:27 pm Post subject:

Paul · Posted: Thu Apr 24, 2008 2:03 pm Post subject:

Hope all goes well.

Let the car sit overnight, if the coolant tank is empty start over.

If it is not empty, fill it about 1/2 way between the lines.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

blackhat · Posted: Thu Apr 24, 2008 2:30 pm Post subject:

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

The coolant reservior tank should be about half full (the extra space in there is too allow for coolant expansion).

There's a line marked "KALT" (german for 'cold') about halfway up the front side of the tank. The coolant should sit close to this level with the engine cold.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

blackhat · Posted: Fri Apr 25, 2008 10:49 am Post subject:

Just curious... is the temp sensor for the temp gauge in the dash on the back of the cylinder head pointing to the firewall? Like where there is no room at all?

The temp gauge in the car is stays maxed out. I'm not sure if it's a short or a bad temp. Anyways, I was looking for the replacement and the closest thing I could find was a DME Temp Sensor (http://www.pelicanparts.com/catalog/shopcart/944M/POR_944M_ELgage_pg5.htm#item23). Is that what I'll be needing?
_________________
My First Porsche
-----------------
1978 Porsche 924 N/A

Paul · Posted: Fri Apr 25, 2008 11:19 am Post subject:

$15 HERE

The one you have is probably OK, more likely your issue is a short in the wire running from the sender (on the back of the head) to the Gauge.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

blackhat · Posted: Fri Apr 25, 2008 2:21 pm Post subject:

Is this it? That little blue guy with no wires on him?

_________________
My First Porsche
-----------------
1978 Porsche 924 N/A