panel ignition light stays on but alternator charging - cause?

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superboots

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I have a VP TMD 22P with the standard panel. The ignition light does not go out on start up or with higher revs. The alternator has been checked and is charging. Any ideas how to find the cause appreciated.
 
I had a similar problem with the warning buzzer continuing and the rev counter not working. Squirting WD40 down the key slot and giving it a good wiggle solved the issue. The key was not going back to the right position.
 
With the engine running both sides of the bulb should be 'high' so no current flows.
Measure the voltage at the WL terminal of the alt. It should be 14 or so. (engine running).

This goes to the bulb. If the other side of the bulb is low, causing the bulb to light, the fault is on the low side of the bulb.
THis is where boats differ from cars, the bulb will often have circuits hanging off it to run a buzzer. This may include diodes.
This varies from engine maker to engine maker, is sometimes messed about with by boatbuilders and owners.
So it's hard to decypher over the forum.
Is there a bleeper and is it bleeping?
You might try removing the wire from the alt and replacing with a simple 2W or so bulb (not LED) to +12V as a test.

When you say 'it is charging', I'd ask if it's putting out the current it should? Do the volts drop if you put a load on it like a couple of headlamp bulbs or any handy load that will pull several amps?

With the engine stopped, removing the wire from the WL terminal of the alt should cause the bulb to go out.
If it stays on, there a fault and it's not in the alternator.
HTH?
 
lw395 said:
With the engine running both sides of the bulb should be 'high' so no current flows.
Measure the voltage at the WL terminal of the alt. It should be 14 or so. (engine running).

This goes to the bulb. If the other side of the bulb is low, causing the bulb to light, the fault is on the low side of the bulb.
THis is where boats differ from cars, the bulb will often have circuits hanging off it to run a buzzer. This may include diodes.
This varies from engine maker to engine maker, is sometimes messed about with by boatbuilders and owners.
So it's hard to decypher over the forum.
Is there a bleeper and is it bleeping?
You might try removing the wire from the alt and replacing with a simple 2W or so bulb (not LED) to +12V as a test.

When you say 'it is charging', I'd ask if it's putting out the current it should? Do the volts drop if you put a load on it like a couple of headlamp bulbs or any handy load that will pull several amps?

With the engine stopped, removing the wire from the WL terminal of the alt should cause the bulb to go out.
If it stays on, there a fault and it's not in the alternator.
HTH?
Click to expand...

It is presumably part of the standard Volvo Penta panel, which does have a buzzer and a forest of diodes interconnecting the the other warning lights with the buzzer!

watching this thread with interest!
 
This is digging 40 years into the memory banks but a modern alternator has 9 diodes. Three of which are to do with supplying balancing voltage. When you switch on the voltage is unbalanced and the warning light is on. Once the alternator is turning it supplies a balancing voltage and the warning light goes out.

I think you may have one or more of these diodes going / gone bad.

NB the alternator still charges normally using the other 6 diodes.
 
TQA said:
This is digging 40 years into the memory banks but a modern alternator has 9 diodes. Three of which are to do with supplying balancing voltage. When you switch on the voltage is unbalanced and the warning light is on. Once the alternator is turning it supplies a balancing voltage and the warning light goes out.

I think you may have one or more of these diodes going / gone bad.

NB the alternator still charges normally using the other 6 diodes.
Click to expand...

The group of three are the field diodes. They supply the field current. If one or more of these failed you probably would not get the full output from the machine.
Perhaps worth getting the alternator tested by an automobile electrician That would eliminate any obscure faults it may have that could lead to "tail chasing"
 
superboots said:
I have a VP TMD 22P with the standard panel. The ignition light does not go out on start up or with higher revs. The alternator has been checked and is charging. Any ideas how to find the cause appreciated.
Click to expand...

Do you by any chance have multiple batteries and a battery isolator unit that manages the charging? I had exactly the same problem when I bought my boat and I isolated the problem to be caused by the battery isolator between the alternator and batteries, incapable of registering the approprriate signal back to the engine.

Try bypassing your isolator and connect your alternator directly to the battery and see if the light goes off. If it does then you have found the cause.
 
benchmark said:
Do you by any chance have multiple batteries and a battery isolator unit that manages the charging? I had exactly the same problem when I bought my boat and I isolated the problem to be caused by the battery isolator between the alternator and batteries, incapable of registering the approprriate signal back to the engine.

Try bypassing your isolator and connect your alternator directly to the battery and see if the light goes off. If it does then you have found the cause.
Click to expand...

Presumably by "battery isolator" you mean a diode splitter?

If so I can see how it might cause the exact opposite, namely light not coming on at all, therefore alternator not getting initial excitation and therefore not generating.

Can't at the moment see how it will result in the light staying on but will have a couple of hours or so later to ponder the imponderables . Will think about it then!
 
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