Got a 95 zx 1.4 I have noticed that when the engine is at normal operating temp with engine off and the ignition switched off the temp and fuel gauges read lower with engine off. When I start the engine these gauges rise. For example the temo gauge goes from say approx 80c to just over 90c when starting the engine and the fuel gauage goes up from say just under a quarter of a tank to just over a quarter of tank.
Is this normal behaviour
Temp Reading
Moderator: RichardW
I guess it's not normal behaviour - but may be common to a lesser extent on most cars.
The reason is that with engine running - the alternator is also running & charging - providing a higher operating battery voltage.
With engine switched off - the battery voltage quickly drops - approx by 1V - especially when loaded (even lightly by your instrument gauges & lights). THIS is normal - even for new quality branded batteries - by the chemical structure of a lead-acid battery.
I donno if your ZX is provided with a voltage regulator for the instruments - probably it is. This MAY be at fault then.
On modern cars (like yours) - this will be a small electronic component soldered into the circuit on the rear of your instrument panel.
On old cars it was a rather clumpsy mechanical unit clipped on by spade terminals - looked like a special designed 3terminal relay.
You definately have to be a wizzard with a low-wattage soldering iron - if repairs on the instrument panel is considered. It's so darned easy to impose lots of other problems/damages to these circuits with a soldering iron.
The reason is that with engine running - the alternator is also running & charging - providing a higher operating battery voltage.
With engine switched off - the battery voltage quickly drops - approx by 1V - especially when loaded (even lightly by your instrument gauges & lights). THIS is normal - even for new quality branded batteries - by the chemical structure of a lead-acid battery.
I donno if your ZX is provided with a voltage regulator for the instruments - probably it is. This MAY be at fault then.
On modern cars (like yours) - this will be a small electronic component soldered into the circuit on the rear of your instrument panel.
On old cars it was a rather clumpsy mechanical unit clipped on by spade terminals - looked like a special designed 3terminal relay.
You definately have to be a wizzard with a low-wattage soldering iron - if repairs on the instrument panel is considered. It's so darned easy to impose lots of other problems/damages to these circuits with a soldering iron.