Tech Note: Starter Solenoid Not Engaging When Hot

[steveb@newkla.kla.com (Steven Buchholz)]

I have been dealing with a problem on the qtc for some time where the 
starter solenoid does not engage when the engine is hot.  I usually have 
to either wait ~15 minutes for things to cool down or push start it (not 
too dignified I must say).  I've been planning to obtain a rebuilt starter, 
and I found out by scouring the parts fiche that there is a heat shield 
that my car does not have.  

Looking at the wiring diagram it shows that the current used to pull in 
the solenoid goes through the start position switch on the ignition switch.
Bentley states that if there is a starter solenoid engagement problem to 
check the grounds and measure the voltage to the solenoid when the starter 
circuit is energized.  A voltage of 8 volts is considered acceptable.  

I got a hold of a copy of *VW* Tech Bulletin Group 27 Number 92-02 that 
talks about this issue on VW cars, in which it states "During cranking, 
the voltage at terminal 50 of the starter solenoid must be at least 10 
Volts.  This value will not be reached by older vehicles."  It then 
discusses ensuring that power and ground connections be checked, but if 
these actions do not resolve the problem that a starter relay be installed.
The bulletin then goes on to describe how the relay would be installed, 
which basically alters the circuit so that the switch actuates a relay
that in turn energizes the solenoid.  The bulletin also includes a parts 
list.  If anyone is interested in getting a copy of the TB, send me a 
direct e-mail and I can fax or mail it to you (3 pages).

It turns out that there is another one of the parts people at Carlsen
named Mary that has put together the kit and has a few for sale.  I 
picked one up from him last night for $20 ... you could probably get 
the parts a little bit cheaper by going to Radio Shack or equivalent.
I'll be figuring out the installation details on the qtc this weekend,
and if I figure out a cool mounting location (pun intended) I'll post 
the info to the net next week.  

Steve
=========|=========|=========|=========|=========|=========|=========|======
Steven L. Buchholz	KLA Instruments Corporation - RAPID Engineering
s_buchho@kla.com	M/S A1-3400, PO Box 49055, San Jose, CA 95161-9055
(408) 456-6244 (office/voice mail)	(408) 434-4284 (fax)

'88 5000CSQ Avant				QCUSA #317
'83 Quattro Turbo Coupe				QTC Registry #?????
'78 Audi Fox GTI 4+5 (ACHTZIG)
=========|=========|=========|=========|=========|=========|=========|======