Sag dash acting strange after 3hrs into drive

[fairclp]

Drove none stop from Basingstoke to Chester this AM.

She's been layed up for 4 weeks so needed a battery charge last night.

Anyway, everything is fine mechanically, but after 3hrs the dash started to display strange readings:

- the oil pressure kept jumping to 68+ causing green changeup light to flash on
- then the battery volts joined in and jumped to 17V most of the time
- then the water temp joined in and hit 117C!

Drove the last 30mins with various combinations happening.

Then I got home... As it idled whilst I checked the oil, everying went back to normal.

I'm thinking overheating dash ECU? What do you think?

[Tangoed]

Hi Paul, I'm just wondering if the voltage regulator on the alternator is working. At idle there ok but when the revs pick up they can throw out high voltages.

[tail slide]

Agree with Tangoed - should put out 13.4-13.6V as rev engine, can easily check with multi-tester off main alternator lead; unfortunately airbox needs to come off to get to it, (take care to plug back in the 3 tubes and air sensor!)

Fluctuating voltage also apparently affects engine ecu, potentially messing up fueling etc.

(edited to correct voltage, not enough coffee yet today....)

Edited by tail slide on Sunday 27th April 09:37

[Jasper Gilder]

Check your 100amp fuse - dashboards playing up are the first sign it's gone

[Targarama]

Sounds to me like something overheated in the dash electronics as you suggest.

The good old 100A fuse shouldn't be ruled out though. Keep one handy...

When the engine is cold my voltage reads 13.9-14.0 Volts, with the occassional 'flash' of 11.9V. Goes away when its warm. Been doing it for a year now... I must get round to checking that fuse myself... (mine still has the original fuse since the car was new).

[KillerJim]

I would go with overheating as this has happened to a few people.

You may be able to 'hear' the small FAN running after an hour or so of driving. I only notice when I stop at a garage and then jump back in, whilst the dash is doing the neddle dance I hear the fan spin up.. but it's got to be warm in there before it kicks in..

James

[fairclp]

Thanks for the replies.

Latest:

Chester to Chatsworth. Nowt. No problems. 2hrs driving.

Chatsworth to Basingstoke: 2 1/2 hrs in temp randomly reports 117C and gradually becomes worse after slowing for traffic and stopping for gas. Pressure sesnor joined in. Volts OK.

I'm thinking temp sesnor now. The pressure is just happening in simpathy.

I'll check out the dash fuse this week. I've got a spare somewhere...

Anyone changed the temp sesnor themselves. I know there are two, which one is which?