4wd indicator light.

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BaileySims
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My tercel:: 1983 Tercel SR5 4WD
Location: Texas
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4wd indicator light.

Post by BaileySims »

Mine has never worked since I have bought the car a few years ago. The only thing I have done recently is change the bulb in the climate control area and I don't think it came on after that either. I have not noticed it until this morning that it started to work somewhat.

As soon as the car is running, the 4wd indicator light comes on and fluctuates with the idle of the car. If I turn the parking lights on, it gets brighter. I'm sure there is a second bulb for that. Switching the 4wd selector back and forth does nothing.

So I think it's obvious that there is some wiring issue somewhere, but where do I begin to look?
WAGON MAFIA.
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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: 4wd indicator light.

Post by Petros »

It is a simple system, study it in the wire diagram, a mechanical contact on the trans closes a circuit that goes to the dash indicator light. First, try looking at the sender where it is supposed to connect to the trans, it is a simple switch, either open or closed (easty test with a volt-olm meter). Inspect that for good contact, no frayed or abrasions on the wire. Than trace it up into the bundle and than up under the dash. check out the contracts on the back of the indicator light, clean it for corrosion, etc. occationally the sender gets damaged or corroded internally and shorts out, but that too is rare, but worth a check out with a volte-olm meter.

Usually once the wire feeds into the cover of a bundle, it should be good until where it is come out the other end (you can see the routing somewhat by studying the wire diagram from the FSM). However, I have had the old plastic wiring insulation get so brittle that the insulation cracks and falls off inside the wire bundle sheath (outer cover, where you can not really inspect it), and short out a system. I found that out after the whole wire bundle melted down and it finally blew the master fuse (which I did not even know this car had). though that is kind of rare, and not likely, but on a car this old anything is possible. It is also possible that mice or other critters chewed through the insulation, that does not happen so much on toyota, but some import cars use soy bean based wire insulation, which is just food for critters.

I once bought a fixer honda4wd civic (kind of rare) for $100, and it sat in a grassy field for three months before I could get to it. When I discovers all of the insulation, and almost all of the rubber boots, grommets, and similar parts, were eaten away, all to bare metal. the whole car had to be rewired, not worth it, so I sold it for parts.

It sounds like your indicator is either grounded by frayed or damaged insulation or contact, or somehow shorting out internally with the other systems. It is closed loop and should not be responding to other switches or systems, so that indicates there may be bare wire on wire contact with an other system. So you need to study the other system affected, and see if you can locate where those two system come together. If any breech of the outer sheath is not obvious (like damage or abrasion through the sheath and several of the internal wires), than your only option is to cut open the sheath and inspect the wiring inside of it.

BUT do that ONLY as a last resort, check all other possible causes first, and visually inspect the wire bundles for obvious outside damage. Most of the system you can check out, all connections, contacts, and external wires, before you have to cut open the sheath of the system.

Good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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