[Healeys] OD actuation problem

[Bob Spidell]

Bruce,

This is a SWAG, but based on the first paragraph I'd say your O/D 
actuator solenoid is almost a dead short.  With any inductive load 
(solenoid, coil, motor), you'll get an momentary (milliseconds) dead 
short then the induced field will produce high impedance, and the 
voltage should return to near nominal.  If it's not the solenoid, it's 
something downstream of the "3-4" switch (assume you're talking about 
the one on the gearbox?).

The throttle position switch is designed to provide an alternate source 
of current to the O/D so you can't disengage the O/D unless the engine 
is driving the wheels.  I'd have to look at the schematic--which I'm too 
lazy to do right now--to be sure, but a defective/maladjusted TPS 
usually doesn't cause the O/D to fail to activate (only to not keep the 
O/D engaged at closed throttle).

Try it again for a few seconds, and see if the solenoid gets (very) 
hot--that'll confirm it's the culprit.  If not, check the O/D 
relay--based on your voltage readings it's not the culprit but, hey, 
it's Lucas ;)

bs


Healey Bruce wrote:
> I plan on contacting the Nocks again on Monday, but here's a question for 
> the list.  Last Saturday, my OD dropped out and would not engage again. 
> Tracing with a volt meter, I found that I had voltage to the upstream side 
> of the transmission selector switch, but when I moved the lever to the 3-4 
> range, voltage dropped to less than 1 volt on the downstream side.  Thinking 
> I had a short in the switch, I ordered a new one, and installed it tonight, 
> but same result.  I also noted that when the lever is moved to the 3-4 
> range, voltage on the upstream side also drops to less than 1 volt.
>
> My throttle position switch has always been pretty useless, with the OD 
> dropping out with very little throttle applied, so I also adjusted it.  I 
> discovered tonight that I have voltage with the throttle depressed about 1/4 
> way, but then lose voltage at somewhere around 2/3 engagement.  I also hear 
> something springing--like the spring is letting go--from the throttle 
> switch.  Would a faulty throttle position switch cause my symptoms?  Is it 
> possible that my solenoid is shorting out?
>
> Bruce Steele
> 1960 BN7
> Brea, CA 
>   
*******************************************************************
Bob Spidell           San Jose, CA            bspidell at comcast.net
*******************************************************************