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Choke heater ALWAYS has power

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Old 02-09-2013, 01:28 AM   #1
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Choke heater ALWAYS has power


Hope someone can help me.

My old faithful 2wd 89 2.4 carb hilux with 520,000 kms on the clock has never let me down, usually stands for 3+ months at a time between use was dead the other day

First I though I must have left a light on etc, it was only used 2-3 weeks before and did a long run of around 600 kms.
Battery has always been good, charge has been good. So I jump started it, drove it to the house, charged battery overnight etc.

In the morning I notice the charge indicator on battery is not green, truck started ok, battery voltage when running was about 12.7 (so not bad, but a little low), as rpm rose it rose a little, still under 13v

Anyway while revving engine from carb noticed the choke heater was hot. thought OK, probably as car running for 10 mins, outside temp was 34 degrees Celsius or 93 in the old money) so a warm day could be normal.

Ayway 3 hours after this, carb had cooled down, choke heater was just as hot.

Ignition IS OFF at this point.

So basically the carb / choke heater is always receiving power even when ignition is off. I know the fuel solenoid is not receiving power with ignition off.

Questions are :-
  • Does anyone know the answer ?
  • What does the other end of this red power wire connect to
  • Is it controlled by some temp sensor somewhere ?
  • I cant find it on any electrical diagrams I can find, does anyone have one that shows this

I am quite good with auto electrics, but without a good manual I am working blind

I read on a couple of choke related threads this comes from the alternator. Is it possible my alternator is faulty and is shorting this wire to positive ?

Hope someone can help, thanks in advance

Andy (Melbourne Australia)
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Old 02-09-2013, 12:13 PM   #2
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Take a look through this page, should answer your questions and walk you through.
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Old 02-10-2013, 12:00 AM   #3
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Thanks for the info

Traced what I could, disconnect the heater, still lots of battery drain.

When I connect the battery I get a loud click (like a heafty solenoid) from the ignition module, when I remove the battery it clicks back. This module is getting warm with the ignition OFF, guess this could be part of my issue

Is there an ignition relay somewhere that has jammed ?

any ideas ?
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Old 02-10-2013, 08:25 AM   #4
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Hopefully the attached pictures show up ok. They apply to 1985 pickups & 4Runners exported to the U.S., but I'm sure there are some similarities based on what you're describing.

As you can see, the Cold Mixture Heater (CMH) relay's "remote wire" is switched by key. The conductor within the relay is permanently grounded. When the key is switched on the magnetic coil is charged within the relay and thus closes the circuit for the CMH coil.

Just to throw a guess out there, but I think the most probable scenario would be that the relay "froze up" and is now operating continuously. Thats just a guess though.

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Old 02-10-2013, 08:54 AM   #5
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Sorry, for some reason I gathered that you were talking about the Cold Mixture Heater. The choke coil heater changes everything I posted previously.

The yellow wire from the alternator is used for two purposes only: to signal the charge light that there is a charging issue AND to power the choke heater (which I think you mentioned earlier).

In the event that the alternator is failing, I wonder if it is possible that a short occurred within the alternator: specifically between the yellow wire mentioned above and the main alternator-to-battery charging wire(s) (those are white). This would keep the choke heater on continuously and MAYBE backfeed towards other carb operating components and igniter.

As a simple test: try testing for continuity at the yellow wire AT THE ALTERNATOR, but you can't unplug the alternator to test it. You'll need to pierce the conduit. Savvy?
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