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Voltage regulator query & Battery Overcharging

BRE Fabrications LTD

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Hey guys,

Ran into an odd issue whilst out in the 80 yesterday. The volt gauge on the dash started bouncing up to the thin line just under the 18v line. The red charge light came on too. The bounce coincided with me hitting around 1800-2000rpm.

I figure the voltage regulator on the alternator has died.

The alternator I have in the 80 is a remanufactured High out put unit (170amp). Its been in the truck for a few years now without any issue. But when I ordered it (from the US) the voltage reg on the new unit was damaged so I swapped over the one from my duff OEM alternator.

Would this potentially have been an issue with it being a higher output alternator?

With regards to the volt garage on the dash, when you are driving should the needle be fairly stable or is it normal for them to lift and drop with the revs, as mine has done for years? I am wondering of this was a sign it was on its way out...

Lastly, when this happened I still had an hours drive home, mostly in traffic so I was able to keep the revs below 2000rpm most of the way. When I did eventually get home I checked the battery which was very hot, don't have a multimeter at home so couldn't check voltage. I went out to see if the truck would start this morning and nothing. I couldn't even get it to turn over.

I have no doubt cooked the battery (Numax 249H). Is there any hope of rescuing it?
 
The voltage regulator is usually a combined regulator/rectifier unit with a given rating so fitting a lower rated one would probably shorten it's life assuming you're actually drawing/using the extra current of the higher rated alternator of course. Not sure about rescueing the battery from a serious over charge. I would probably say not, unlike a deep discharge which can sometimes be saved. I once grossly overcharged a sealed type battery and the sides were bulging, due I suspect to plate warpage. Maybe a battery expert can chime in. The only time I notice my OEM voltage gauge move is when a put a big load on the electrics, particularly the intake pre-heater which pulls around 45-50A, when the gauge reads slightly lower. Can't say I've ever noticed it move up and down with engine revs though. Alternators produce good output from very low revs unlike the old dynamos which didn't!
 
Hey guys,

Ran into an odd issue whilst out in the 80 yesterday. The volt gauge on the dash started bouncing up to the thin line just under the 18v line. The red charge light came on too. The bounce coincided with me hitting around 1800-2000rpm.

I figure the voltage regulator on the alternator has died.

The alternator I have in the 80 is a remanufactured High out put unit (170amp). Its been in the truck for a few years now without any issue. But when I ordered it (from the US) the voltage reg on the new unit was damaged so I swapped over the one from my duff OEM alternator.

Would this potentially have been an issue with it being a higher output alternator?

With regards to the volt garage on the dash, when you are driving should the needle be fairly stable or is it normal for them to lift and drop with the revs, as mine has done for years? I am wondering of this was a sign it was on its way out...

Lastly, when this happened I still had an hours drive home, mostly in traffic so I was able to keep the revs below 2000rpm most of the way. When I did eventually get home I checked the battery which was very hot, don't have a multimeter at home so couldn't check voltage. I went out to see if the truck would start this morning and nothing. I couldn't even get it to turn over.

I have no doubt cooked the battery (Numax 249H). Is there any hope of rescuing it?

Hi Ryan
As tow pack says the voltage should not rise and fall with the revs, and if that has been doing since you changed it.
Thats what a regulator does is keep the voltage at one level, but you can get different values, as if you are doing short trips a higher value is better but if you were doing a lot of motor way miles then a lower value
 
Try Robson and Francis for a replacement. They remanufacture and offer good warranties. Speak to Mike, he may be able to get you a new correct regulator. 020 7733 2353

As above, replace the battery.
 
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