Re: [DML] RPM counter problem

[Warren Wallingford <warren@xxxxxxxxxx>]

I see Chris Almy has responded with some good advice and analysis.  The 
problem is RF interference with the tach caused by too much resistance 
in the ground circuit.  There are two other important grounds to find 
and clean.  The first is where the battery itself connects to the frame 
on the RH trailing arm bushing mount.  Make sure the cable end is clean 
and the M8 bolt tight against the frame.  The second ground is the main 
ground for the front of the car: fans, fuel pump, headlights, etc.  It 
is located behind the LF wheel where the radiator stay is bolted to the 
frame.  A gang of black wires is tied to ground there with an eyelet.  
Take the M6 bolt out, clean everything and re-install.  Gronk it down 
pretty tight to make a good physical connection.  This ground circuit 
goes back to the battery through the connector located in the washer 
bottle well.  If there is still trouble after you clean these two 
grounds, the the problem will be in there.  It's an awful pain to get to 
and work on, but at that point, there is no choice.  Good Luck.
Warren at DMC


John wrote:
> Hi All,
>
>    I am looking for some advise on my rev counter problem..
>
>    When I run the car the rev counter works correctly...
>
>    I then switch on the air conditioning switch to either 'max' or 
>    heater and it still works ok..
>
>    However as soon as I then switch on the fan the counter leaps up by 
>    a couple of thousand RPM (The engine does not actually change by
>    this amount) and the counter then leaps about with a mind of its 
>    own !!
>
>    Obviously some electrical problem but not sure where to start ??
>
> Regards
>
> john.
>
>
>
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