Strange Charging Issue
Discussion
My 1983 2.8i has developed a strange electrical issue. I noticed the voltmeter was showing a low reading, just down into the red area showing low voltage.
I changed the alternator for a new rebuilt one. Identical item except 65A output instead of 55A. Happy with that.
When the car is at rest, the voltmeter registers about 13V. Voltage at the battery terminals with engine running about 13.9V. Revving the engine makes little difference.
However, as soon as I start to move - no lights or anything else on, the voltmeter drops to just above the low red zone and stays around there for as long as I'm on the move.
When I stop, the voltmeter climbs back up slowly to 13V or thereabouts. Could an ageing battery be the cause, although it starts the car from cold with no problem. I'm struggling to know why movement makes a difference.
Can anyone throw any light on this mystery? Thanks if you can.
I changed the alternator for a new rebuilt one. Identical item except 65A output instead of 55A. Happy with that.
When the car is at rest, the voltmeter registers about 13V. Voltage at the battery terminals with engine running about 13.9V. Revving the engine makes little difference.
However, as soon as I start to move - no lights or anything else on, the voltmeter drops to just above the low red zone and stays around there for as long as I'm on the move.
When I stop, the voltmeter climbs back up slowly to 13V or thereabouts. Could an ageing battery be the cause, although it starts the car from cold with no problem. I'm struggling to know why movement makes a difference.
Can anyone throw any light on this mystery? Thanks if you can.
Use a known good multimeter to measure the voltage across the cars voltmeter and battery when on the move
Once the cars voltmeter has been proven to be accurate........
If while on the move the voltage at the cars voltmeter is proven to be low compared with that at the battery, use a multimeter to find if the voltage drop is along the voltmeter ignition supply or its earth
Investigate what's happening with the charging circuit If while on the move the battery voltage and cars volt meter readings are low
Once the cars voltmeter has been proven to be accurate........
If while on the move the voltage at the cars voltmeter is proven to be low compared with that at the battery, use a multimeter to find if the voltage drop is along the voltmeter ignition supply or its earth
Investigate what's happening with the charging circuit If while on the move the battery voltage and cars volt meter readings are low
I no longer own a wedge, but.....if you consider a basic charging system. the red light is on because it is battery backed and the zero volts (ground) from alt or gen makes it glow.
As your alt/gen starts to turn it produces 12v (or more) so there is 12 volts on both sides of the ignition lanp , hence no current flow, no glow.
Your voltmeter is not wired correctly, it is possible you or the previous owner (it's always the P.O.
has the voltmeter connetcted to the black 12v run.
If you want to read volts correctly it must be grounded. However Fibreglass car....check your grounds.
As your alt/gen starts to turn it produces 12v (or more) so there is 12 volts on both sides of the ignition lanp , hence no current flow, no glow.
Your voltmeter is not wired correctly, it is possible you or the previous owner (it's always the P.O.
has the voltmeter connetcted to the black 12v run.If you want to read volts correctly it must be grounded. However Fibreglass car....check your grounds.
Before getting to deep into this simply measure the battery voltage whilst driving and see if it does the same as the gauge.
If it does then finding the fault will be fun.
If it does not then the fault is the gauge or its wiring which i would advise you leave alone as getting at the instrument will involve lots of work.
Steve
If it does then finding the fault will be fun.
If it does not then the fault is the gauge or its wiring which i would advise you leave alone as getting at the instrument will involve lots of work.
Steve
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