Rear Window Defogger not getting juice

[xirdneh]

My wifes '83 Tercel has a non working rear window defogger
None of the wires show any sign of doing anything when the window is fogged
I checked both potential feed wires for juice and got no reading (one on each side of window and i do not know which one is supposed to be the hot wire)
The Relay Switch is on the passenger side and it passed the FSM check test (removed dash speaker cover and speaker to get at it)
The 30 AMP Circut Breaker is on top right of drivers side fuse panel and it tested ok too
The 7.5 fuse (labled "GAUGE") was ok too (second one from bottom on right side of driver side fuse panel) this fuse covers Defogger, Back-up lights, some Gauges and one of the Heater speeds)

One of my Tercel buddies told me to check the wires in the short section that goes from the body to the rear door
The wires flex everytime the rear door is opened and shut
Eventually hardening the copper and making it crack
He found this to be true on a non-Tercel that he worked on
On that car the wires used had more strands than normal to help prolong the life of the wire

Has anyone had any experience with this?

[rer233]

i'd say your tercel buddy is right- check where the wires go from the body to the hatch. i've had 'em go bad on more thah one occasion. he's also right about having extra strands making 'em more flexible. rather than trying to splice cheapo wire in at the flex point, i cut the broken wire on the body side (in the right side tailight area as i recall) splice in a length of new cheapo wire, repair the broken wire, and pull the repaired part into the hatch (all repairs soldered and shrink-wrapped of course.) bit of a PITA, but then the original factory wire does the flexing. good luck!

[Petros]

yes, the place where the wires pass from body to door is a common source of this kind of issue. I guess no one expected these cars to last this long so these kind of things will happen.

You can test the wires by pushing a sharp pin into each on either side of the bend and use a volt-olme meter on them.

[splatterdog]

On any door jamb wire repair, don't use just ordinary primary wire. It isn't nearly as flexible as automotive wire. I had to repair a broken wire on a minivan's powered slider. 3 months later broke again. Not in another spot either, it was the new section of wire from an autoparts store spool.

I use these guys now- http://www.waytekwire.com/products/

[splatterdog]

yes, the place where the wires pass from body to door is a common source of this kind of issue. I guess no one expected these cars to last this long so these kind of things will happen.

You can test the wires by pushing a sharp pin into each on either side of the bend and use a volt-olme meter on them.

You can, but it's not advisable. Without sealing the hole, corrosion will occur. I've stopped using these test leads for that very reason.http://www.cdwg.com/shop/products/Fluke ... 96431.aspx
Makes it easy, but can cause future problems

[ARCHINSTL]

I, too, have had a problem with the defogger wires; some test OK and some do not. So far, so good.
Now, electricity and moi have an agreement; if I don't mess with it, it won't harm me or Goldie.
This stems from when I left the ignition on too long back in '07 and fried the igniter (and other dizzy parts).
Now, this may sound naive - but here goes...
Can I simply unplug the green IIA connector to the distributor and then leave the ignition on as long as necessary to trace the broken wires without doing harm to any other circuit?
Thanks,
Tom M.

[splatterdog]

Tom, that will certainly isolate the ignition. Might want to unplug the alternator too.

When checking door wires, scutinize all of them. I had to completely rebuild a drivers door harness on an early 90's Camry. 3-4 wires broken, over half the others had cracks in the insulation, did them all. Pain in the butt, as it had power windows,locks,mirrors,door panel light and speakers. But it was NLA from anywhere in the world except for junk yards. I'm sure there were a few good harnesses out there, but the time to try and find them was better spent on just fixing the car.

It's easiest to drop the roof liner just enough and rear door panel so you can pull the top half of the harness out. Fighting it in place is tough. Also, they can be broken internally with little evidence on the outside. Rarer, but it happens. Flex the wires as you test them with a meter. Depending on door position, the broken ends can touch sometimes.