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Originally Posted by David N.
Thanks for the advice, I went in today and started testing, here's what I got:
In conditions where the car was idling at 0mph, coolant temp at 93 degrees Celcius, the following values were on Relay 8:
85 - 4V
86 - 13.5V
87 - 13.5V
30 - 0V
I shorted 30 to 87, fan did activate (which kinda figured cuz the fan does indeed work just not at the right times). Upon seeing 0 at terminal 30 first, I checked the B4 fuse, but it seemed to be fine. So I'm guessing at this point it's a bad relay. Anyone know what values at terminal 85 and 86 should cause 87 to close with 30? I guess they are cheap enough to replace and see, but given the nature of the compartment fan, I'm going to have a tough time ascertaining whether or not it's fixed outside of going on some spirited driving again.
BTW, it says '53' on top of the relay. Is that all I need to identify it for replacement?
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Hi,
The relay is just an ordinary SPST automotive relay with a Coil rating of 12VDC, 160mA, 400 ohms.
SPDT Relay : (Single Pole Double Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87).
When the coil of the relay is at rest (not energized), the common terminal (30) and the normally closed terminal (87a) have continuity. When the coil is energized, the common terminal (30) and the normally open terminal (87) have continuity.
The diagram below center shows the relay at rest, with the coil not energized. The diagram below right shows the relay with the coil energized. As you can see the coil is an electromagnet that causes the arm that is always connected to the common (30) to pivot when energized whereby contact is broken from the normally closed terminal (87a) and made with the normally open terminal (87).
The Dealer Repair manual does not give the specific terminal values. But, since the relay is pretty cheap, $5-$7, I'd simply change it, they do wear out. This price would be for a standard Bosch SPST Relay. If you want the Dealer Part, it is part# 141.951.253.B and lists for $16.
Another possibility would be the Temperature Switch for the engine compartment. It might be wise to make sure that it's electrical connector isn't corroded and tightly connected. Here's what the DSM says about this Switch:
Temperature Switch for the Engine Compartment
An NTC thermistor is installed between the intake pipes of cylinders 1 and 2 in order to measure the engine compartment temperature.
The DME control module activates the engine compartment fan depending
on the respective engine compartment temperature and various additional
factors.
But, I'm betting that the relay does the job for you. Hope this helps...
Happy Motoring!... Jim'99