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Discussion Starter #1
So my 1984 RRC project (recovery) has progressed and is more or less done. There are a few issues which keep popping up and one of them is that I have yet to find an alternator that will put out a steady 14.8v or thereabouts.

So the original alternator was bad. The ign. light never went off and it was not doing anything much. I replaced with a Bosch Rebuild (Lucas) unit 80A. This started to show a strange behaviour where the voltage would fluctuate from 12 to 14v at about 2Hz independent of engine speed. It made the lights go all wonky. After 500 odd miles I just now replaced this with a BBB industries rebuild Lucas which gave out 14.7v for about 20 seconds and then died. This one has the ignition light NOT come on when starting and then there is no output at all. Unlike the Bosch one the BB is really fried.

I have now ordered a true Bosch 110A alternator and am waiting for that to arrive: https://www.ebay.com/itm/282998893734?ViewItem=&vxp=mtr&item=282998893734

I do have a fair bit of electric load: 2x90W fans (typically only 1 running) AC and Sniper EFI with electric fuel pump. Then I have (normal) headlights adding to the load when it is dark, but no winch or floodlights or on anything. I did not check for amps (need to get a clamp A-meter) but with the Bosch unit it did get very hot, which makes me wonder if I just have an abnormal load and the Bosch unit was trying while the BBB unit just gave up. If there was a wonky cable surely the battery would die. I checked the battery by the way (new) and it seems to be good with correct volts and charging current (through battery charger), it also cranks healthy.

The original wiring uses the starter motor terminal to collect all the high current connectors (batt, Alt, etc), which is a bot crowded and near the exhaust. I am planning to place a 200A fuse on the fender and then route the wired to there with just a single wire powering the starter.

Any other ideas?
 

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Discussion Starter #3
Well good point, I have not. But I did measure the voltage between the alternator (+) and battery (+) and found about 0.1~0.2V which would indicate a decent connection between the two. Of course I don't know how many amps were flowing, I bought a DC clamp Amp meter which should give me a better indication of what is going on.
 

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this failure almost points to bad grounds and or power cables, in a nutshell as toadhall suggested resistance. in layman's terms the alternator's output is trunked thus it overloads the diodes and voltage regulator.

you have the charging output, just nowhere to flow. at 34 yrs of age I would not hesitate to renew and update all power and ground cables as well as a good cleaning of terminal locations.
 

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I second the suggestion to check your ground. I went through 2 alternators in a few months, and it was because one of the engine ground cables was not connected properly.
 

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Discussion Starter #6
So checked all the connections, cleaned, measured and retorqued. All good. Still waiting for alternator 3 (4 counting the original) to arrive. This time I purchased a real Bosch 120A alternator, non of this Lucas rebuild stuff. Last one I sent back was just washed I think you could see rust inside. From BBB industries: Quality products from Alabama! said Mexico on the sticker.

In the mean time I received by Clamp Amp Meter and did some measurements. Engine idling, no AC, no fans, no lights (base load): 14A. AC on fan full on 1 engine cooling fan on head lights on: 44A. Add one more fan and I suppose 50-odd Amps max load. So I was not really overloading the alternators.
 

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I think the highest draw I ever had on an alternator has been around 60 amps running a 1000 cca megatron plus battery, 4 hella 550'a lit, headlights lit, a/c on and winching while at night at idle.
120 is more than enough for an old stock vehicle with out soo many ecu's.
 

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Discussion Starter #8
RESOLVED. Fitted the 'proper' Bosch alternator (very nicely refurbished with a new, real Bosch 14v regulator) and guess what: 13.9v at battery, steady at idle, pulling about 15A (baseload). When I load it up the output goes to about 30A (at idle) and the voltage drops to about 13.5V, little bit more rpm and it right back to 13.9 - 14.0V.

Yes I checked the cables but there was nothing much wrong there. I basically bought 2 dud 'overhauled' Lucas alternators. Many British cars run happily on Lucas alternators so I am sure they are good, but I think maybe the expertise to overhaul them correctly is lacking (in Mexico), or maybe the components available are just poor quality.

Good, now I can move on with all the other age-related fixes. Just noticed I lost a mudflap. The PO had cut it to clear the exhaust, I on the other hand just fitted the exhaust right. Age and a starting tear made the mudflap last 350miles only.
 

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It is regrettable, but typically, a "cheap" alternator is serviced with aftermarket parts, with a limited tolerance for current capability. Name branded units typically will use quality parts, and are worth the additional expense. One other possibility is that the battery was severely discharged, or damaged, creating an internal short. This will typically add a significant load to the alternator, which can overheat even a good unit. You might consider, in the future, charging the battery with an external charger before installing the alternator. That will allow you to check the battery, and keep a significant load off of the new unit. Ray
 

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Discussion Starter #10
Thanks Ray. My battery is new and I kept it charged with a charger as the alternators(s) were being so temperamental. I agree that quality of components is real issue unless you pay top dollar, which gets costly if you resurrect a 30-odd year old car. My believe in refurbished alternators is a little chattered after this experience. In the end I did get a good one for decent money.
 
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