Rear Defroster ???

[triggerman454]

Evenin'

Seems like the rear defroster quit. Get out the factory manual and have checked all ( but the ETACS unit. I am only getting 1-2 volts at the pins on the Diagnostics connector. Can't seem to find this unit under the dash as layed out in the wiring configuration diagram. I've had problems with the alternator circuit and need to check the inputs to the unit. Thanks

[x2xtreme360]

I've done some pretty hefty diagnostics work on my old 3S to get the rear def to work... turns out the etacs was bad. HO let me grab a diagram.

[triggerman454]

I've done some pretty hefty diagnostics work on my old 3S to get the rear def to work... turns out the etacs was bad. HO let me grab a diagram.

Thanks for the reply. I'm getting too old to be crawling under the dash on these little cars.

I was thinking of just bypassing the unit a install a relay using the original switch.

[x2xtreme360]

I basically just cut out the extra crap and simplified the diagram.


Rundown: The switch on the dash sends a ground signal to the etacs unit at pin 10 or 12 (depending on whether you have anti-theft or not). The etacs unit then sends a ground signal out from pin 5 or 3 (anti-theft or no anti-theft) to energize the defogger relay coil. The relay switch then closes, and sends a hot feed to the defogger at the rear of the car. Very simple system.

Easiest thing to do is to start with the relay in the engine fuse box. Remove the relay and check pins 3 and 5 for hot feed when the car is in the "ON" position.

If those check out good, test pin 1 for ground when you press the defogger switch. If you don't get a ground, move on to the defogger switch itself.

Make sure pin 1 at the switch is getting a good ground all the time. Check pin 6 at the defog switch for ground when you HOLD DOWN the defogger switch (it wont stay grounded if you let go of the button). If you get a good ground when you press the switch, move onto the etacs unit (to the left of the steering wheel. You have to remove the lower dash panel to access it. Looks like a little cheap-o box thing with two connectors coming out of it.)

Once you find it, check to see if pin 10 (without anti-theft) or 12 (with anti-theft) at the etacs unit is getting a ground while the defog switch is PRESSED AND HELD DOWN. If you receive a good ground at that pin on the etacs unit, there's three possibilities.

1) The etacs unit is not receiving sufficient power and/or ground supplies (not likely if other things are working, such as anti-theft or power windows are working for a short period of time when you turn the car off).
2) There is an open circuit in the wire between pin 5 or 3 at the etacs unit and pin 1 at the defogger relay.
3) The etacs unit on that circuit has gone bad. Need to replace the entire unit.

[triggerman454]

Thanks for the info. Just got home from work and I've decided to rewire ( install some jumpers ) and make the circuit as in my Firebird whereby it's just an "on & off" switch controlled deal. All this complexity is as waste IMO.

My first car was a 1954 Chevy Bel Aire....Oh for the simple days .


Thanks again !!!!!!

[triggerman454]

Got it. At least on paper. Install this weekend.

Green/Yellow from relay and Black from defroster switch ( indicator lamp ) thru toggle switch to ground.

ETACS Eliminated. !!!!!!!!

Thanks

[x2xtreme360]

What I did (to keep it stock) is swapped over the little mechanism inside the fog light switch that keeps the button pressed down.

It took me a little bit to figure out how it worked, but the fog light switch is an actual toggle type switch. Since I didn't have fogs, I simply opened up the unit, found the mechanism that kept the button pressed down, and installed it in the defog switch. It retained the stock switch, and I just turned it off manually. I just rewired the relay coil ground over the to open side of the switch, and voila!

[triggerman454]

GREAT!! I have to run down to "Pull A Part" and get a switch off a GT 3000 since I do have the fog lights. Will wire it up and leave the wires accessible and use the toggle switch temporarily til i can rig up the switch. Thanks !!!

Pull-A-Part: Used Auto Parts For Less - Pull-A-Part