electronic instruments off scale high

[clasabro]

As soon as the ignition is switched on all the electronic instruments go off scale high.
Looks as if they all have a positive and earth in common so I am guessing I have a bad earth, anybody know where to start looking?

[mrzigazaga]

Hi mate


Check and clean all the earths first...

1. N/S rear rocker cover x 2...
2. N/S suspension turret
3. Battery earth to engine
4. Black and white bullet connectors under the AFM from dissy
5. Coil

Then check all fuses.

[wedgewood]

I'm sure I read somewhere that the instruments are earthed to the bonnet release or bonnet cable. Someone on here will hopefully confirm this or correct me.

[adam quantrill]

yes that can be the case, As the bonnet cable is steel, over the years the contact can get pretty iffy.

You can run an earth strap from the bonnet pull bracket through the bulkhead grommet to the earth point on the rear of the cylinder head. It helps no end. Copper braid is best - about 1cm wide.

[clasabro]

Earth is good to the bonnet catch, but no sign of how it gets through the bulk head catch bolts must be buried in the fibre glass. What looks like expanded aluminium grill stuck to the glass has an earth if you scratch about but I cannot see where it is connected to the instruments

[adam quantrill]

The instruments are earthed to the bonnet pull bracket. The bracket is connected to the bonnet catch by the (dodgy) pull cable. The catch is earthed to the block (I think) by a copper braid.

So the earth passes through the bulkhead along the bonnet pull cable.

[clasabro]

That's so ridicules I didn't realize wha r wire from the bonnet catch earth strap through the heater hose bulk head penetration, I have connected it to the bonnet release bracket rev counter still flying off scale oil pressure climbing slowly off scale.disconnecting at sender end makes no difference. i think its time to take the dash off and see what is going on. I have been going too for a while to sort the oil pressure warning light that has no continuity from the sender.

Edited by clasabro on Saturday 1st July 13:33

[SEvans]

Not sure about the 350 but my earlier Tasmin has a voltage regulator mounted behind the dash on the right hand side. I've not looked into how it works or in what ways these can fail but it's something that is common to all the instrument gauges. May be worth a look. Cheers Steve

[clasabro]

Thanks sounds like a good candidate will take alook