P38A Battery indicator

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domino

domino

Well-Known Member
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Location
Edinburgh
Hi all. 4.0 bosch

Jumped in to the car for the first time in a week and noticed the battery indicator flickering. Gave it a few blips of the throttle and it seemed happier so on I went to collect my daughter from nursery. Got to about half a mile from the nursery and it came on again, dash lights dimming. Blipping seemed to resolve it but didn't want to end up stranded at the nursery so came home.

Checked with a multimeter and the output from the alternator seemed to be all over the show. From 3v to 14.5+. Again, giving the throttle a blip seems to fix it but it would occasionally drop again before coming back up. Then let it sit on the multimeter for 5 minutes idling and it was putting out a steady 14.6-14.7 volts.

I've seen some posts mention a diode and others mention an issue with slipping belt. With the vague info above, can anyone suggest the most likely issue.. And if its a DIY fix or a replacement alternator?

Thanks,

Martin
 
Knackered brushes/slip-rings. Time for a new alternator probably.
Mine is a 150A alternator on a 4.6L Thor.

They can be had "exchange" fairly cheaply.
 
Last edited:
domino said:
Hi all. 4.0 bosch

Jumped in to the car for the first time in a week and noticed the battery indicator flickering. Gave it a few blips of the throttle and it seemed happier so on I went to collect my daughter from nursery. Got to about half a mile from the nursery and it came on again, dash lights dimming. Blipping seemed to resolve it but didn't want to end up stranded at the nursery so came home.

Checked with a multimeter and the output from the alternator seemed to be all over the show. From 3v to 14.5+. Again, giving the throttle a blip seems to fix it but it would occasionally drop again before coming back up. Then let it sit on the multimeter for 5 minutes idling and it was putting out a steady 14.6-14.7 volts.

I've seen some posts mention a diode and others mention an issue with slipping belt. With the vague info above, can anyone suggest the most likely issue.. And if its a DIY fix or a replacement alternator?

Thanks,

Martin
Click to expand...
Most likely worn out brushes in the alternator. A new regulator/brush set can be had for not a lot, there was a link posted recently. The kit I bought had new slip rings included. It's an easy job to overhaul an alternator.
A slipping belt is possible, but is unlikely with the serpentine belt.
Bad connections are another possibility such as the earth strap from engine to chassis.
 
Datatek said:
Bad connections are another possibility such as the earth strap from engine to chassis.
Click to expand...

Measuring from the alternator to positive terminal would rule out the earth strap though, wouldn't it? Which is what did.

I'm guessing the brushes then. I'll see if I can find that link!
 
Datatek said:
Most likely worn out brushes in the alternator. A new regulator/brush set can be had for not a lot, there was a link posted recently. The kit I bought had new slip rings included. It's an easy job to overhaul an alternator.
A slipping belt is possible, but is unlikely with the serpentine belt.
Bad connections are another possibility such as the earth strap from engine to chassis.
Click to expand...
Hi Keith,
I tried to go down this route but I found that the brushes were not only worn down but they had created two grooves in the "spinny-bit" that were deeper than the trenches on the death-star. So I bailed and got a new one (cowardice under fire I think). :D
 
DanClarke said:
Hi Keith,
I tried to go down this route but I found that the brushes were not only worn down but they had created two grooves in the "spinny-bit" that were deeper than the trenches on the death-star. So I bailed and got a new one (cowardice under fire I think). :D
Click to expand...
The rotor?
 
DanClarke said:
Hi Keith,
I tried to go down this route but I found that the brushes were not only worn down but they had created two grooves in the "spinny-bit" that were deeper than the trenches on the death-star. So I bailed and got a new one (cowardice under fire I think). :D
Click to expand...
The slip rings can be replaced.
 
Fun continues. No battery light now (haven't done anything) but I do get the display flickering like mad between things like rhf door open and the mileage
 
Last edited:
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