Hi all,
In the wiring posted here for 2010 Fusion/Milan, I see that defrost says "pulse one time to turn on, pulse a second time to turn off".
However when testing this I found that pulsing did not turn on the defrost indicator lamp (it does work for the seat heaters). The test method was to pierce the wire with a fine pin then momentarily ground the pin with a jumper wire, this is kind of old school but it works.
I then did some searching and found the post linked below, which indicates that the defrost has to be latched and not pulsed.
So I tried latching it and the defrost light still did not come on.
I had to button the car back up but would like to understand this before I proceed with my project - is it that I should not expect the indicator to light up if I've latched the circuit (which appears to directly control the coil on the relay, but this doesn't make a lot of sense to me - where is the timer?).
Any help is appreciated.
Link to (old) post - I didn't want to post in such an old thread:
https://www.the12volt.com/installbay/forum_posts.asp~TID~118473~PN~5~TPN~5If you used a dmm to test, in most of the newer ford products it is a WHITE/ orange wire that is negative or ground latched signal for rear defrost/defogger. In the few fords I've hooked up rear defrost to remote starts it did not turn on the indicator but I tested at the defroster grid with a meter and indicated it was infact on.
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Thank you. It was the WHITE/ orange I was testing. I should have tested and looked for voltage at the defrost grid.
The original poster from the thread I linked to responded to a P.M. and let me know that the indicator does not come on when his system is latching the wire to ground.
So its clear that instead of being a signal pulse this is actually pulling some current to ground and activating a relay. I am guessing the timer is built into the control panel itself.
It looks like I can use an ordinary 2222 NPN transistor to latch this safely as the wiring diagram shows there is a diode across the relay in the SJB (GEM module). I am also assuming I have to diode protect the control panel and my own curcuit from each other (two diodes).
I'm going to try and dig up a generic 12V relay from my parts pile (love junkyards!) and see if that will work for 15 minutes and not fry the transistor, all this stuff is kinda new to me and I'm learning as I go.
If your remote starter has a negative signal defroster wire, all you need to do is hook it into the cars defroster wire. You can use a diode if you like, but I don't think it is necessary. Here is a pic from a 2010 Fusion HVAC module where I tapped in. Depinned wire is defroster.
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