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Author Topic: '84 AHB Thermoquad choke  (Read 249 times)

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'84 AHB Thermoquad choke
« on: December 30, 2018, 17:22:27 »

For a while now it seems that it takes forever for the choke to let off on my AHB with a thermoquad. It seems that it takes almost until the engine is at operating temperature for the choke to let off.

I did some checks and it seems the choke control may be bad, but not 100% yet.

I was just curious does anybody have any idea how long it should take for the choke to let off. on a cold day, maybe about 60 degrees?
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Re: '84 AHB Thermoquad choke
« Reply #1 on: December 30, 2018, 17:51:02 »

It should gradually start opening as it warms up. It can be a mixture of clogged choke passage in the intake or something wrong with the electric element that causes problems.


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Re: '84 AHB Thermoquad choke
« Reply #2 on: December 31, 2018, 09:28:02 »

There are two types of Electric Assist Choke controls and the difference is primarily around what levels of voltage is supplied to the choke heater given the ambient temperature.

1) Single Stage
Below 55F electric heat is not available until engine approaches normal operation temp.
Above 80F electric heat is shortened.

2) Dual Stage
Summer electric assist heat is 'hotter' than winter, the resistor accomplishes this.
Above 80F electric heat is "full throttle", meaning the resistor is bypassed and the choke heater element gets the full voltage. Below 55F that heat is reduced since the resistor is in force.

Here is the control unit test procedure (directly from my 1980 'Engine Performance Manual', section 25-11):
(1) Check test light by connecting between battery terminals of car battery. Take careful note of bulb light "intensisty". (Dual Stage Control Only).
(2) Before starting engine, remove ignition harness electrical connector from control switch.
(3) Connect test light to load (choke) terminal of control switch and to ground.
(4) Start engine and allow to reach normal operating termperature.
(5) Apply 12 volts to ignition harness terminal of control switch. If test light does not light or does not have same intensity as step (1) above, control switch is defective and must be replaced.

If you need one of these just tell me what type you have, I most likely have a pile of these in a box somewhere...if I can toss this into a bubble-wrap envelope it'll be just the cost of postage. Given how tiny of a part it is though you may find that local auto parts store may have a reasonable price on them anyways, maybe even less then the postage...LOL!?
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