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> Thermotine question, D Jet issues
robkammer
post Jan 9 2026, 01:57 PM
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Happy New Year Teeners! Sorting out some small issues on our BB, and I'm hoping that someone can share some testing specs for a thermotine sending unit. I'm assuming it meters a 12volt signal from the control unit to the AAR. But as assumptions go, that's where I am.
Also, does anyone know if these are still available? Or does anyone have one in good working order they'd like to sell?
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ejm
post Jan 9 2026, 02:39 PM
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Your picture is a decel valve
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Superhawk996
post Jan 9 2026, 02:50 PM
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The thermoswitch controls the cold start injector. Has nothing to do with the AAR.

The thermoswitch and cold start injector don’t even come into play unless vehicle and ambient temperatures are around 32F and below.

Review the Anders overview of d-jet operation and components.
https://pbanders.synology.me/914/djetfund.htm

Thermoswitch can be tested by placing in the freezer and then monitoring continuity with a DMM as it warms back to room temperature. It should be closed when it first comes out and then should go open as it warms towards ambient.
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JamesM
post Jan 10 2026, 01:38 PM
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QUOTE(robkammer @ Jan 9 2026, 12:57 PM) *

Happy New Year Teeners! Sorting out some small issues on our BB, and I'm hoping that someone can share some testing specs for a thermotine sending unit. I'm assuming it meters a 12volt signal from the control unit to the AAR. But as assumptions go, that's where I am.
Also, does anyone know if these are still available? Or does anyone have one in good working order they'd like to sell?
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The thermotime switch is just that, a switch. On/off. Unless it is broken it ONLY comes into play at VERY cold temperatures (below freezing) and while cranking. Has no impact on how your 914 runs (though a leaky cold start injector will) it only impacts sub freezing starting performance.

For most people these days you can eliminate the cold start injector completely with no impact on your 914 experience as most people dont start their 914s in sub freezing weather anymore.


The device in your hand is the decell valve, though that one appears to have been modified/plugged. Also can operate the car without that though some believe running without it may overstress the MPS diaphragm.
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