Anybody know anything about the Ford heated windshields

[junkyardjeff]

I got my old 89 crown vic back and the heated windshield has been replaced with a regular version,now the rear defroster does not seem to work even though the switch lights up that its on. Both operated by the same switch and I do know the windshield had its own temp sensor and would not come on after a certain temp leaving only the rear to come on,now with the heated windshield gone something is now open and not allowing power to get to the rear. I do have a factory wiring diagram and need to study it but not sure what to jump or hook up to make the rear defroster start working.

[wayne petty]

i wonder if mods were done up front..


there is an alternator output current switch or relay..  that takes the alternator output and sends it to the heated windows.. but at the exact same time. another relay commands the alternator to full field.. or close to it..  changes the output voltage from 14.4 volts to over 80 volts.. while the car and battery get NO charge from the alternator for the few minutes the heated windows are on..

my CV manuals and wiring diagrams booklets have been boxed and the boxes shuffled several times.. its like a 3 shell game with over 100 stacked office files boxes that are in different rooms and closets.  it might take all day to find them.

if you want to photograph or scan the various diagrams.. i will be glad to look at them and try to assist you.  only if you want..

i currently only have some of the underhood diagram.. not where the front window and rear window wiring goes..

you can create an imgur.com account and upload them there as an album really easily.. if you upload several at a time and set the upload to private..  like these.. https://imgur.com/a/KC0tF  but like i said.. i don't have the wiring for the connections to the windshield or the rear window defroster..

[junkyardjeff]

The wires for the windshield were just cut off and left laying on the cowl,nothing in the shop manual about if its replaced with a non heated unit, Looks like a complicated system to try to bypass.

[wayne petty]

warning.. those cut off wires could have close to if not 100 volts on when if you flip the switch..

i don't know if or how the rear window defroster is wired in..

that requires the diagrams you have..

please secure the ends of the wires.. with proper electrical tape.. or self vulcanizing silicone tape followed by a layer of conventional 33+ 3m tape.

i would really worry about operating the defroster switch without a load of the windshield on the alternator..  it will be really easy for the alternator to go well over 100 volts and blow the diodes..

[junkyardjeff]

Wires capped and taped up,been looking at the wiring diagram and can not see anything I can do to try to make it work. The shop manual has a short wiring diagram for the heated windshield and it shows what looks to be a jumper wire at the control module near the glove box for the unheated windshield but does not go into any detail,there is a windshield current sense resistor to prevent it from working if the windshield breaks so I wonder if it senses something wrong with it not hooked up.

[junkyardjeff]

I found the wires for the rear defroster in the trunk and its getting power so I must not have left it on long enough to warm up,it ;looks like it does not kill the whole system with the windshield out of the circuit.