I'll try to tomorrow when I can see what I'm doing.
99 Taurus cooling fan runs only when heater is on.
- Thread starter JN94
- Start date
I'll try it and update with the results.
Red wire running from the battery to the fuse box ?
No. According to the wiring diagram on the first page the computer activates the relays via the red wire pin 61.
Vehicle electrics and wiring are beyond my abilities.
If the wiring diagram on the first page is correct, I see no way that the fans would still work with the relays pulled out unless the load side wiring of the load side relay pins for both relays is shorted together.
You can at least unbolt it and get a look at the bottom. It should be apparent if anything has cooked or corroded. You can also use that wiring diagram and a test light to see if you have power to the wrong relay pins (with the relays removed).
You should probably unbolt it and look underneath it to see if you see any obvious wiring damage. Those fans are getting power somehow if you have the relays removed.
When testing the female pins in the fuse box that the relay goes into, you should have two powers and one ground per relay and this is with the circuit loaded so key on, engine off.
There are two sides to a relay. One is the control side which are pins 85 & 86 in the diagram which when activated, closes the switch on the load side which are pins 87 & 30 which operates the load which in this case are your fans.
The control side of the relay will have one power and one ground. The load side will have one power which on the diagram is pin 87 on the high side relay and pin 30 on the low side relay. On the diagram it's hard to determine which pins on the control side are supposed to be power and ground but in a lot of cases, the PCM will provide the ground for the control side. You will have to use a test light on pins 85 & 86 for both relays to determine which is which but that is if you have the correct signals going to them.
I used a test light already. 2 out of 4 pins have power.
Update: Finally figured it out. At some point , someone had attempted to run what looks like a toggle switch. I found a small wire that had been ran from the relay box to the fan harness. Once I got it back to how it should be , the fans went back to working normally. Now they do not work without the fuse or relays.
