Gauges and electrical gremlins

["jchapelhow" <chapelhow@xxxx>]

All

In order to continue the diagnosis of my overheating problems I have 
invested in a non-contact digital thermometer. Point the laser beam 
at an object and, hey presto it tell me how hot it is. No more 
guessing or burnt fingers!

It would seem that my immediate, genuine overheating problems have 
been corrected by the new silencer/cat-bypass. After a 25miles run, 
both pipes to and from the thermostat recorded ~65degree-C. Even 
allowing for a 15-degree-C difference across the metal of the pipe 
the cooling system is doing the business. The cooling fans therefore 
do not need to come on at all, which Martin and others advised was 
the best indicator of excess heat being generated.

The problems now seem to be electrical with all of the gauges doing 
some very strange things.
·	During the trip, the temperature gauge in the car varied 
wildly, settling at around the 10'oclock position. When the ignition 
switch is turned off the gauge initially settles to zero. Then it can 
be watched to climb to point straight up, ie beyond the normal top 
scale. Indeed on several occasions the needle settled pointing to the 
letter P, of `temp'. The gauge rises very quickly if the lights are 
switched on, faster as each greater level of illumination is used. 
The temp gauge also moves when the interior cooling fans are turned 
on/off.
·	The voltmeter now rarely indicates above the 8v mark. 
Occasionally is will read 10v if the car is revved at idle. Attaching 
a voltmeter across the battery shows it to be OK, and starting is 
fine. New 130amp alternator is standing by but the car has a Motorola 
that appears to work correctly.
·	The oil pressure gauge, for which a new sender has been 
fitted, does not read beyond the second line. The pressure has been 
checked by external equipment and is OK. The gauge moves about 
through an angle of 30degrees and back when the door sensors are 
open/closed.
·	Petrol gauge reads low. The car has a full tank of fuel, but 
points to <quarter full.
·	The direction indicators are not behaving either at idle at 
junctions the indicators do not start working, if the throttle is 
blipped they start, but I am not confident that they are working as 
quickly as the should. Hand signals through the minimal window are 
not a good option!

I am guessing that there is either a bad ground or a short somewhere. 
All of the relays/fuses have been upgraded. The new lock zilla and 
fan fail 2x2 work normally. I had planned to change/clean the relay 
for the direction indicators but the manual shows this (and the 
windscreen control module, logic/buzzer box) next to the left hand 
bulkhead. No such device is immediately visible. (Still trying to 
trace the buzzer noise)

I have briefly connected a jump cable between the ?ve battery post 
and the engine ground point which made no difference.

What are the next steps to diagnose where the problem lies? The car 
itself drives very well, and the engine now revs smoothly. I am 
concerned though that I am being denied meaningful warnings of actual 
problems, and I am now spending too much time staring at the 
direction indictor bulb to see if my signals are being shown to other 
road users.