AE86 Heater Control Light

[Super86]

I'm trying to get to the bottom of why the light isn't working behind the centre console heater control. It shows around 12v when the lights are switched on, though the bulb says 14v on it. Any ideas as to why this would be happening?

[Ivan141]

If you have 12v and the bulb is good, then the ground path is missing.
14v is a reasonable rating.. with the alternator working voltage goes a little bit
above 14v.

[Super86]

(07-10-2016 10:26 PM)Ivan141 Wrote:  If you have 12v and the bulb is good, then the ground path is missing.
14v is a reasonable rating.. with the alternator working voltage goes a little bit
above 14v.

Awesome, thanks. How am I best to track down the missing ground path?
Cheers
Simon

[Ivan141]

Look it up in the manual if its in there. I believe theres a ground point around the center console somewhere.

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[FanIsHere]

If you try putting it on the other side maybe? Led bulbs do that -work on a particular side.

[Ivan141]

Is your bulb ok? Did you test it already? Also, did you put any LED replacement bulbs in, in which case you might want to try plugging it in the other way around.

The dash lighting is grounded through junction box nr1, which is in the driver side footwell.
If something was wrong there you would have more serious problems than just some lights not working. So I'd guess you've either got bad light bulbs, or a broken wire.
Does your cigarette lighter still work?

[Super86]

(07-12-2016 10:02 AM)Ivan141 Wrote:  Is your bulb ok? Did you test it already? Also, did you put any LED replacement bulbs in, in which case you might want to try plugging it in the other way around.

The dash lighting is grounded through junction box nr1, which is in the driver side footwell.
If something was wrong there you would have more serious problems than just some lights not working. So I'd guess you've either got bad light bulbs, or a broken wire.
Does your cigarette lighter still work?

Yes, the cig lighter works and everything else (inc heater control) works 100%. i've actually tried another bulb and neither work, which is an unlikely coincidence that they both didn't work. They are just the factory bulb, not LED. i'll check the junction box NR1 - thanks again.

[Ivan141]

Dont bother with the function box if your lighter still works.. It uses the same ground. Use a multimeter and measure the following things:
-Voltage at both pins of your light bulb socket (with the lights on obviously).
Should be 12V on 1 side only. if its 12V on both pins something is wrong.

-If you found only 1 pin with 12v, measure continuity to ground from the other pin (some bolt on the chassis is easiest to use).

If both are ok (12v + good ground), then the bulb should light up when you put it in. If it doesnt the only explanation I can think of is high resistance in the 12v wire, but havent come across that in practice so far.

[Super86]

(07-14-2016 11:48 AM)Ivan141 Wrote:  Dont bother with the function box if your lighter still works.. It uses the same ground. Use a multimeter and measure the following things:
-Voltage at both pins of your light bulb socket (with the lights on obviously).
Should be 12V on 1 side only. if its 12V on both pins something is wrong.

-If you found only 1 pin with 12v, measure continuity to ground from the other pin (some bolt on the chassis is easiest to use).

If both are ok (12v + good ground), then the bulb should light up when you put it in. If it doesnt the only explanation I can think of is high resistance in the 12v wire, but havent come across that in practice so far.

Thanks again - it was a bad ground path. Cheers