contaminated
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| posted on 13/11/08 at 11:03 AM |
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Odd rev counter behaviour
All - I have a strange problem with my rev counter.
I have a set of smiths dials and all but the rev counter are the newer reproduction jobbies - so the bulb holders themselves are earthed. The rev
counter is an older item, and on these there is a live only to the bulb holder and the lamp is earthed through the case.
In terms of wires to the rev counter there is a total of four - a signal, a live, an earth and then the live to the lamp.
I thought the rev counter earth would be enough to earth the bulb as well. But when the car is running and I switch the lights on the rev counter
dies! This must be an earthing issue.
Short of changing the bulb holder to a newer self-earthing one, any ideas?
ta
Dan
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02GF74
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| posted on 13/11/08 at 11:30 AM |
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Well looking at your wiring diagram, .... oh, hang on there is no digaram so we have to guess once again ....
So more questions.
Presumably the engine is still running?
Does the wire for the tacho come from the coil or ecu?
Does the tacho lamp light up?
Do the other instrument lamps light up?
Are you able to measure the voltage on the power supply to the tacho?
Is the case of the tcho connected to earth or switched?
Can we rule out a faulty tacho?
As describe, with earthed case, there is no reason for this instrument not to work.
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MikeRJ
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| posted on 13/11/08 at 03:29 PM |
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It sounds very much as though the earth you have on the tachometer housing is poor/high impedance. Putting current through a poor ground raises
it's potential, this is what would be stopping the tachometer working.
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contaminated
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| posted on 13/11/08 at 04:50 PM |
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quote:
Originally posted by 02GF74
Well looking at your wiring diagram, .... oh, hang on there is no digaram so we have to guess once again .... No wiring diagram, just wires!
So more questions.
Presumably the engine is still running? Yes
Does the wire for the tacho come from the coil or ecu? Coil
Does the tacho lamp light up? Yes
Do the other instrument lamps light up? Yes
Are you able to measure the voltage on the power supply to the tacho? No
Is the case of the tcho connected to earth or switched? Connected I think
Can we rule out a faulty tacho? I think so - other than this it works fine and was tested before I got it
As describe, with earthed case, there is no reason for this instrument not to work.
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contaminated
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| posted on 13/11/08 at 04:50 PM |
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many thanks
quote:
Originally posted by MikeRJ
It sounds very much as though the earth you have on the tachometer housing is poor/high impedance. Putting current through a poor ground raises
it's potential, this is what would be stopping the tachometer working.
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