Electrical Fault
Discussion
The problem
When the key is turned in the ignition the fuel guage moves from empty to full
When the head lights are on side lights or dipped beam the fuel guage shows empty or somtimes 1/4 full.
When indicating right if the lights are on both the indicator and the rear light blink ie when the indicator is on the red light is out and when the red light is on the indicator is out. (I think the same happens with the break light)
And just the other day the amp in the boot for the two extra speakers mounted behind the seats started cutting in and out and now only works when the lights are on dipped beam.
Assuming that I have an earth problem I've checked the following ...
Near side front earth strap wire is ok (a bit rusty but multi metre shows connection between engine block and earth wite)
Drivers side front earth strap is ok
Battery is good
The Amp in the boot seems to have both a good earth and 12v supply off the battery
Not sure where to look next - under the dash or in the boot around the light or wires in between - any ideas please
Thanks
When the key is turned in the ignition the fuel guage moves from empty to full
When the head lights are on side lights or dipped beam the fuel guage shows empty or somtimes 1/4 full.
When indicating right if the lights are on both the indicator and the rear light blink ie when the indicator is on the red light is out and when the red light is on the indicator is out. (I think the same happens with the break light)
And just the other day the amp in the boot for the two extra speakers mounted behind the seats started cutting in and out and now only works when the lights are on dipped beam.
Assuming that I have an earth problem I've checked the following ...
Near side front earth strap wire is ok (a bit rusty but multi metre shows connection between engine block and earth wite)
Drivers side front earth strap is ok
Battery is good
The Amp in the boot seems to have both a good earth and 12v supply off the battery
Not sure where to look next - under the dash or in the boot around the light or wires in between - any ideas please
Thanks
Morph,
the amps a multimeter draws is "zero" so does not prove anything. Especially since (perhaps the earth of) your fuel gauge manages 1/4. These bimetalgauges are not multimeter quality with regards to amps used.
As to the rearlights, take off their white covers inside the boot, and check for resistance between lampfittings and common earths. Here are nasty galvanized steel shrinkfits, that may be cprroded. Ford Escort construction fault. Anybody knows how to solder this galvanized (zinc) stuff?
Speakers, hope they do not depend on chassis earth return. Missing earth may roast some transistors in your amplifier. I would not use audio untill you solve this.
mvg Boudewijn
the amps a multimeter draws is "zero" so does not prove anything. Especially since (perhaps the earth of) your fuel gauge manages 1/4. These bimetalgauges are not multimeter quality with regards to amps used.
As to the rearlights, take off their white covers inside the boot, and check for resistance between lampfittings and common earths. Here are nasty galvanized steel shrinkfits, that may be cprroded. Ford Escort construction fault. Anybody knows how to solder this galvanized (zinc) stuff?
Speakers, hope they do not depend on chassis earth return. Missing earth may roast some transistors in your amplifier. I would not use audio untill you solve this.
mvg Boudewijn
It may not necessarily be and earth fault. Some of the instruments will show visible changes in reading for very small variations in voltage(0,2volts).
A common symptom with the ignition switch supply is that gauges vary as diffent circuits are switched on/off but here it is the supply connections that are the problem.
You really need a digital multimeter for checking as very small variations in voltage are often involved.
You can always run a test earth wire direct from the battery and connect it locally where you suspect a problem; use thick wire and ALWAYS connect to the battery via a fuse just in case the wiring colours and the circuit diagram dont match (TADTS).
A common symptom with the ignition switch supply is that gauges vary as diffent circuits are switched on/off but here it is the supply connections that are the problem.
You really need a digital multimeter for checking as very small variations in voltage are often involved.
You can always run a test earth wire direct from the battery and connect it locally where you suspect a problem; use thick wire and ALWAYS connect to the battery via a fuse just in case the wiring colours and the circuit diagram dont match (TADTS).
ijbd said:
As to the rearlights, take off their white covers inside the boot, and check for resistance between lampfittings and common earths.
The rear light clusters are a common source of problems with S electrics. I had headlights flashing on and off with the indicators 
If the cluster(s) prove to be part of the problem, I wouldn't bother trying to make good - just replace both, they are less than a tenner from your local Ford dealer..
SS2. said:
ijbd said:
As to the rearlights, take off their white covers inside the boot, and check for resistance between lampfittings and common earths.
The rear light clusters are a common source of problems with S electrics. I had headlights flashing on and off with the indicators If the cluster(s) prove to be part of the problem, I wouldn't bother trying to make good - just replace both, they are less than a tenner from your local Ford dealer..
Almost certainly the problem , mine failed the MOT because the lights were all operating together, new Mk 4 Escort bulb holder and a squirt of WD40 on the connector block,job done MOT issued.
Hi
Thanks for all the info, electrical contact cleaner on the plug attached to the light cluster seems to have done the trick for the rear light / indicator.
But the Amp in the boot is still cutting in and out and the fuel guage still reports when the lights are on or off (lights off = tank full / lights on - tank 1/4 full) so I guess there is more bad links to find!
Thanks for all the info, electrical contact cleaner on the plug attached to the light cluster seems to have done the trick for the rear light / indicator.
But the Amp in the boot is still cutting in and out and the fuel guage still reports when the lights are on or off (lights off = tank full / lights on - tank 1/4 full) so I guess there is more bad links to find!
Morph,
to test this, switch the lights on (including the contact key) and start taking the volts across all electrical connections in the headlight circuit from earth to plus.
Any contact that is more than, say 0.5 V, is bad and should be improved.
Because the headlights take 10 A or so, perhaps such a bad connection would even heat up enough to be felt with your fingers after a few minutes.
Start from the earthside, because that is the likeliest side.
mvg Boudewijn
to test this, switch the lights on (including the contact key) and start taking the volts across all electrical connections in the headlight circuit from earth to plus.
Any contact that is more than, say 0.5 V, is bad and should be improved.
Because the headlights take 10 A or so, perhaps such a bad connection would even heat up enough to be felt with your fingers after a few minutes.
Start from the earthside, because that is the likeliest side.
mvg Boudewijn
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