940 alternator - voltage regulator melted

BarelyRunning

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Alternator wasn't working, turns out this reg with maybe 5k on it has melted. My car did get very hot recently, so I've just put a new radiator in. Are there any other reasons this may have happened?

TL_V70

Is it Genuine Bosch or a knock off?

I would say something had failed internally in the reg

BarelyRunning

TL_V70 aftermarket Meyle unit. I hope they're OK, as I just used another.

TL_V70

BarelyRunning I have no experience with the meyle type I prefer genuine but if DMC vouchers for them there probably fine.

I highly doubt radiator heat had any affect as I have never seen any regulator melt in hi engine temp situations.

Did you happen to look or feel the slip ring with your finger. Its the copper rings the 2x carbon brushes on the regulator run on in side the alternator. I only as as in one photo the brushes look brand new not like thay have been running on the slip ring and then what looks like to be possibly an arc mark on the white body of the regulator. But the faces of the brushes are what caught My eye.

dmc

check the wiring connections, a 940 should be solid mounted so no rubber mounts and earth wire, just the big red one to charge the battery.

as a test, with engine running check voltage at the alternator (big red one) and then at the battery. if different keep digging, likely a damaged connection or cable.

Meyle are usually very good. cannot see a hot radiator causing that damage, more likely heat from loads of current.

BarelyRunning

On the note of high current draw, I do have 4x LED spotties, would these cause the reg to melt?

dmc I checked voltage at the battery and alternator before repair, but only voltage at the battery after repair. Connections seem great, but if there's a large voltage drop, I may upgrade the thin wiring.

TL_V70 are they supposed to be smooth?

jamesinc

BarelyRunning how much current do they draw? You can just divide the wattage by 12 (volts) to get current in amps, will be close enough.

Overcurrent is the only thing I can think of. Had you been running it with a cooked battery for a while? That would be hard on the regulator.

TL_V70

BarelyRunning

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This is just bosch new bosch regulator but see how tjere are ripples on the face at the end of the brushes there like that new and your brushes are the same. They should be smooth after wear 5000km I would assume these ripples would be gone.

If ypu spotlight are drawing 30amps is with 4 on + all the load of the car the Alternator migh be at its upper load but shouldn't melt the regulator unless the Alternator is glowing hot.

The regulator doesn't directly handle the Amperage of the Alternator so it shouldnt melt. The regulator is just switching low current on and off to the brushes which it turn is telling the Alternator to turn on and off to maintain the 14.5v nominal charge rate. Theres a few other things going on but this is just a simple explanation.

What brand and type of spotties like James said it fairly straight forward to work out whay they draw. And you should have the 2 pairs fused independently so 2x 20a fuses not 1x40A fuse. Eg 2 complete sets of spotlights just turned on by the same switch.

BarelyRunning

jamesinc well the website doesn't list the specs for them except for Lumen output, so I'm not sure. They do use a 40a fuse, but I'm running two sets and two harnesses, so I'd likely be near the limit. Battery is pretty new, high CCA rating.

BarelyRunning

TL_V70 I'm running two harnesses, both fused at 40amp. After some poking, they're rated at 12.5a each, 25a a set. They are operated by the same switch, so a 50a load on my poor 80a alternator is not ideal.

I'm tearing my hair out because I saved a 100a alternator from my wreck and have turned the house upside trying to find it.

It's a 16v b234f, which uses a different alternator pulley than the usual redblock, so I'm not sure if a 100a unit would bolt on. I do have a b230 block + 16v head on the horizon though.

dmc

hmmm, simple question, how big is the alternator? 80 or 100 amp?

Major Ledfoot

BarelyRunning It's a 16v b234f, which uses a different alternator pulley than the usual redblock

More than that, the B234 uses a different alternator body to a B230 redblock. They don't interchange easily.

BarelyRunning

Major Ledfoot b230+16v is getting closer (if I find my 100a alt which I've searched emails, messages, posts with no results)

Major Ledfoot

BarelyRunning If you're doing a B230 with 16V head, you can use the B230's alt bracket. The B234's brackets are very different.

Meaning the B234 and B230 alts are also very different - see thread from 2017 and pics.

https://ozvolvo.org/d/6939-6939/4