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Re: Radiator Fans - 2 relays Posted by Gary Stottler [Email]  (#1463) [Profile/Gallery]
(more from Gary Stottler) on Tue, 12 Jul 2011 12:40:35
In Reply to: Radiator Fans, Pat, Thu, 7 Jul 2011 16:37:34 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Pat,
Nice to hear so many working on 99 Turbos out there!
Here's the deal on 99T fans:
Both fans are controlled by the same thermal switch and both are powered through the same fuse. However, there are two separate relays (one for each fan) with the difference being that one relay gets it's "signal" power from a "battery" (always live) circuit and the other from an "ignition" (live when key is on) circuit. One of the relays is held onto the bottom edge of the relay housing with a little screw. Hence, both relays close when the ignition is on and the thermal switch closes, but only one relay closes when the ignition is off. What the switch on the dashboard is doing (this is an owner modification, by the way, didn't come from the factory that way) is to ground both relay signal circuits so that you can force the fans on without the thermal switch being closed. However, the need to do this means something else is wrong with the cooling system (my 2 cents, anyway - I have the switch wired up in my car but haven't used it in years except to cool down the engine before shutting it off once I got everything else fixed).
In your case, your "ignition" fan is not running, which means that either you are not getting 12V from the ignition switch to the signal circuit on the relay, or that the wiring to the fan or the fan itself have a problem.
Check the 2-pin connector down near the bottom of the radiator where the fan plugs into the wiring harness to make sure that it is tight, not corroded, etc. You can also apply 12V directly to the fan using jumper leads to that connector to make sure that the fan itself works. If that connector is good and the fan itself runs OK when you jump 12V to it, next take a look at the relays. To identify which relay is which, turn on your dash switch so your "battery" fan is running, then pull out the relays - now you know which is "battery", and by default the other is "ignition". Now turn the switch on and off and you should hear that relay click on and off (or check the signal circuit with a volt meter to see that it gets grounded when you turn the switch on).
If all that is working OK, then you get to the most likely culprit which is that the terminals under the fuse block which carry the current from the fuse to the relay have gotten loose and/or corroded over the years to the point where there's no current flowing from the fuse to the relay and then to the fan. The only way to really fix this is to cut off the female terminals and replace them with new ones. I had so much trouble with this that I ended up putting in two complete new circuits with modern blade-type fuses - the original set up is just too borderline to carry the current for 2 fans.
I hope that helps - if you're still having trouble, send me a note off-line and I can try to sketch the wiring for you. Do you have a copy of the wiring diagram for the vehicle?
Good luck!
Gary
posted by 198.208.15...
_______________________________________ Gary Stottler
, Tue, 12 Jul 2011 12:40:35 <-- Viewing This Message
, Fri, 8 Jul 2011 10:38:13
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