4KQ: No power to thermo-time switch after cranking

Ti Kan ti at amb.org
Sat Feb 22 13:51:25 EST 2003

Russ Maki writes:
> On my '87 4000 quattro, I get plenty of current in the cold-start circuit --
> as long as the starter is cranking. Once the engine fires (which it does
> almost immediately) and I let off the starter, voltage to the cold start
> valve drops to zero and I have to nurse the gas pedal to keep it running.
> Could my starter solenoid be defective? If so, my local rebuilder has some
> 'splainin to do.

The thermo-time switch/cold start valve only gets power during cranking,
so that's completely normal.  Your after-start problems are caused
by other ailments, not the cold start circuit.  I would check the
coolant temp thermoswitch that feeds the ECU, and the usual CIS
troubleshooting stuff.  Use your Bentley manual as your guide.

2003 A4 1.8T multitronic
2001 S4 biturbo 6-sp
1984 5000S turbo
1980 4000 2.0 5-sp
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   ///   AMB Laboratories, Sunnyvale, CA. USA
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