Unexpected BBQ... generator reg

[Harv]

Paging Dr Rob, Dr Rob..... autopsy required in Theatre 3.

Number 1 Son's VL has been off the road for the last month or so. He managed to spin #4 main bearing, so a full rebuild was in order. In the meantime, he has been thrashing driving the FB. Most of the stuff that he has been broken is probably coincidental. Got a phone call from him a few days ago to tell me that the FB generator light was staying on. Fan belt still in place and tight... doesn't sound good .

Got myself home, and checked under the bonnet... not pretty. The firewall around the generator reg has black soot, and there is a good circle of soot underneath the bonnet. The D and F wires that connect the gennie to the reg are burnt out - bare copper. The wires either side of the reg are heat affected. Looks like the gennie has spat out a heap of amps, and the wiring did not handle it. Lucky she didn't burn to the ground . I don't know what worries me more - that it could have burnt whilst unattended, or that it burnt while Number One Son was driving it. Neither case good.

I have run the car for around 7 years now. About 4 years ago she did a fully-laden trip up to Taree (4 kids and a trailer), and managed to boil the battery. Topped the battery up and putted around for a fortnight before coming home. Got as far as Newcastle and the gennie light came on. NRMA came to take a look, and played with the contacts in the reg. Suspect that he had less of an idea than I did, and pushed close the contact that prevents the battery backfeeding the wiring - all the magic smoke came out of the gennie. He was more than a little sheepish. Car came home on a tilt-tray, and I fitted a gennie and reg from the spare parts department. Being stupid, I did not check either . Drove OK for the next 3 years, though tended to kill batteries every 18-24 months. Had a new battery in it this winter. Battery was working OK, though the "see through indicator" occasionally went clear ("bad battery" indicator) and occasionally could hear "fizzing" after shutting the car down (my bad... should have investigated more).

The FB has been parked in the naughty corner. Will replace the wiring and take out the reg and gennie in late January. Know I have a spare reg (the one from the Taree trip above), and suspect I have a gennie. Might do the smart thing this time and get Rob's help (please) to run them over the test bench before installing.

Cheers,
Harv

[ardiesse]

Harv,

Sorry - been on Christmas-cake-cooking duty, soon to be chorister for Nine Lessons and Carols -

I think what's happened is probably a D+ to DF short in the wiring (if Prince of Darkness) or a DF to ground short (falls deine Lichtmaschine aus deutscher Herstellung ist). The fact that the DF wire at the generator's fried suggests that it too took some serious current. With the fault in the wiring, the poor regulator will have been unable to limit the generator's output, and the "fuse" in this case will be the generator's field coils, which will have gone open-circuit. Unfortunately the regulator's collateral damage. The short occurred, then the field coils burnt out, and only then the generator light came on.

It'll be some fun unwrapping the wiring harness and replacing the cooked wiring.

Tell me: Lucas or Bosch? I have many Lucas generators, but no Bosch generators in good enough condition to part with. Are you in Sydney over the Christmas-New Year week?

Rob

[gpi]

I know it’s only a FB Andrew, but this would save yourself from misery a forth time:

http://www.fbekholden.com/forum/viewtopic.php?t=338

[Harv]

Thanks gents. Definitely want to put a generator back on. I've got a couple of alternators, but they don't "feel" right.

Its a Prince of Darkness setup.

I'm off on the annual camping trip for the fortnight after Christmas, then home for a week or so before work. Will give you a yell once we have gotten back. No rush on this one - probably a good excuse to put a few miles on Grace's ute.

Cheers,
Harv

[Craig Allardyce]

I converted my regulator Harv. http://www.fbekholden.com/forum/viewtop ... 95#p196455
Still running the generator.

Just an option.

[Errol62]

That’s what I’m planning to do on my ute. When I got it it was running alternator with electronic regulator crudely mounted on the inner guard and original still intact. 25amp fuse is a good idea.


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[Harv]

Autopsy photos... not for the squeamish.

Optimized-IMG_0539.JPG (1.41 MiB) Viewed 909 times

Optimized-IMG_0540.JPG (753.82 KiB) Viewed 909 times

The inside of that reg is horrible, and smells like bad substation.

Spliced in a new harness end, and polished off most of the soot marks from under the bonnet.

With many thanks to Rob for finding donor organs (generator and reg) to get the FB back on the road.

Cheers,
Harv (master magic smoke releaser)

[Errol62]

Good work keeping the FB rolling fellers.


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[Craig Allardyce]

Harv fit an inline fuse to the wire at the starter that feeds to the generator regulator. It offers protection for over currents in the generator circuit especially if the cut out coil doesn't open below the required rpm. If the cut out coil doesn't open the contacts (battery power to regulator & generator), this has the affect of the battery trying to drive the generator and can cause the damage you have.

[59wagon]

Harv fit an inline fuse to the wire at the starter that feeds to the generator regulator. It offers protection for over currents in the generator circuit especially if the cut out coil doesn't open below the required rpm. If the cut out coil doesn't open the contacts (battery power to regulator & generator), this has the affect of the battery trying to drive the generator and can cause the damage you have.

Sounds like good advice Craig. What size fuse would you recommend?

Cheers,

John

[Craig Allardyce]

I run a 25 amp fuse, just above the maximum charge rate of the generator/regulator settings.

[Harv]

This is wise advise Craig.

I watched the NRMA play with the cutout contacts in the FB one afternoon. He pushed closed the cutout, and 5 seconds later the magic smoke came out of the generator. They do not like being fed battery power.

Cheers,
Harv

[ardiesse]

Autopsy Results: Internal short from D+ to ground, occasioning over-current fault in the armature with consequent rapid and terminal effusion of smoke followed by death.

OK, then. Something went wrong at the back of the generator. The plastic insulators that insulate the D+ brush holder from ground got hot and softened. Under brush spring tension, the brush holder rotated outwards until the head of the brush lead attaching screw contacted the frame of the generator. Now we have a direct short to ground. At this point the short is supplied by both the armature and the battery.

Armature first: Rapid overheating with charring of both insulation and slot wedges. The slot wedges partially fall to bits. The armature still produces current, because in this model of Lucas generator the coil ends are staked into the commutator, not soldered. The positive brush lead melts and isolates the armature from the short circuit.

Battery second: The battery joins in the fun once the D+ terminal goes short to ground, and still supplies current into the generator after the brush lead burns out. The wiring from the starter to the regulator to the generator overheats and burns. I would have expected the regulator to notice the reverse current from B+ to D+ and open the cutout relay, but it didn't. Maybe the contacts welded shut. The cutout relay and current regulator now smoke up. At some point the short circuit is cut (maybe the regulator contacts opened?) and the smoke stops coming out.

Contributing Factors

1. The crappy design of the "Pommy-style" C40 generator with Quick-Connect terminals. There is maybe 3 mm clearance between the brush lead retaining screw and the generator frame. On the ground side, it's not a problem, but on the D+ side, you are relying on correct clearances to avoid short-circuits. There isn't even an insulator on the inside of the yoke above the brush holder. The insulators for the D+ brush holder and terminal are nylon, or some similar plastic which softens when it gets hot. And when they get hot, the brush spring rotates the brush holder outward, enough to short on the yoke. In contrast, the Australian-made C40 generators have a commutator cover band, screw terminals and big slots in the yoke for brush access. The slots and the commutator cover band between them provide a lot more room around the brush holders, and the D+ brush lead attaches to a tab on the yoke, rather than to the brush holder. The insulators on the D+ brush holder are Bakelite.

2. Does the FB have headers? Somehow, a whole lot of heat got shone onto the rear of the generator which started the whole thermoplastic insulation softening thing.

Rob

[Harv]

Many thanks Dr Rob. The detail is pretty damn cool.

The FB has a set of Jack Myers headers that run down past the starter. Four cast iron primaries into two secondary pipes (just above the starter), then merge to a single pipe just under the firewall. The headers are close enough to make tightening the rear pipe slip-joint bolts a pain (I have a special bent spanner to do them, Holden part number HARV-0044). Could well be the source of toastiness. I'll take a look once I'm home again, may need a heat shield or some header wrap.

Is there any chance of the back bearing getting hot enough to initiate the damage? I am somewhat remiss in not oiling the back of the generator very often (or vaseline-ing the dizzy cam for that matter either).

Cheers,
Harv

[ardiesse]

Harv,

I don't think the rear bearing overheated. On disassembly there was still plenty of oil on the shaft and bush.

I was wondering instead how close the front exhaust pipe goes to the generator.

Autopsy 2 (Lucas C39): thrown solder from commutator. The growler tells me the armature's a mess of short circuits.

Rob