QuestionI have the same problem, Was trying to follow your advice but Im unsure what you mean by pins 1-4.
I have a Chilton manual but its pure garbage for electrical.
I disassembled part the ac controls trying to find the problem, too many wires I don't know which ones are going to what and I also noticed using a volt meter both sides of the grid are grounded?
One is grounded right to the body near the grid, and the wire going to the front of the car is coming up as grounded???
Is there another relay other then the one hooked to the Ac controls?
AnswerHi Harvi,
I assume that you are speaking of the rear window defogger that David asked about a couple of days ago. The pins I spoke of are those at the relay in the trunk, on the fender. That is the only relay involved in the circuit.
The power is supplied to two pins of the relay on the black/pink wire. It comes directly from the power distribution center under the hood via a fusible link wire coming immediately from the battery cable clamp. So see if you have 12V on those pins. Then the black/white wire is the one that goes to the grid on the driver's side. That wire should be apparently grounded, but really not because you are just seeing the resistance of the grid (which is very low between it and the ground point on the other side of the grid). So that is normal. What you need to have happen, when you request the rear defrost, is for the relay to click (have a helper listen to the relay) which is caused when the voltage on the relay's dark blue/white wire (which before you requested should show 12v (because it is connected through the low resistance relay actuation coil to one of the pink/black wires) changes to read 0 volts (i.e. the request grounds that db/w wire, which actuates the coil, closes the relay and sends the 12v current thru the relay switch contacts to the grid wire). Now that grounding of the dark blue/white wire happens either because the request switch grounds it (in the manual temp type of controller) or the body control module grounds it (in the automatic temperature controller). The body controller is told to ground it by the request switch in the ATC control panel which is the only differnce.
So with that information, check it out and let me know what you find to be your situation. It could be several reasons for your defrost not working but by methodically checking the relay's voltage situation you should be able to identify the cause.
Roland
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