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1973 TR6 alternator issues

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ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
I have a 1973 TR6 which is running the original Lucas alternator. I know, right? spinning smiley sticking its tongue out The Prince of Darkness has finally struck. The "Ign" light came on a few days ago but the alternator is putting out some voltage. I read 14 volts at the battery with a volt meter.

In diagnosing the problem I discovered that a weld has separated in the plate diode to the "S" or "+" plate. If I press the broken spot weld back together the "Ign" light goes out and the battery voltage rises to 14.5 volts. I don't see any way to spot weld the connection back to the plate so I believe I am in for a new alternator.

The first question I have is what is a good replacement alternator that will require the least amount of customizing to get it to fit. Then, I see that the newer alternators are 3-wire units. This Lucas is a 4-wire unit. It has a 3 wire plug with two large brown wires and a smaller brown/yellow wire. Then there is a separate spade lug wire that I am not sure what it does.

So, when converting to a 3-wire alternator how are the four wires used? confused smiley

Thank you,
Gary

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In most cases, it will be the wire to the separate terminal that goes unused. You can just tie the wire back, but be sure to do so securely as it is always hot and has no fuse. (I suggest not cutting it off, in case you need it for the next alternator.)

There is a Bosch unit that is a direct drop-in (including the 3-way plug), but they are getting hard to find; your FLAPS probably won't have it in stock.

One fairly decent option IMO is to take your old alternator in and ask to have it rebuilt. My local independent store can have it back in 3 days (sometimes 2 if business is slow at the rebuilder).

PS, the Bosch units I've seen also take the 4th wire. Original application is 78-79 Ford Fiesta with A/C (sometimes given as with Bosch alternator). Cars without factory AC used a Motorcraft unit that won't fit.


Also, looks like RockAuto has a clone of the Bosch unit for $57 outright (no core), which seems like a good deal (but might not be, caveat emptor)
http://www.rockauto.com/en/moreinfo.php?pk=6676688&cc=1128271&jsn=432&jsn=432
http://www.rockauto.com/en/catalog/ford,1978,fiesta,1.6l+98cid+l4,1128271,electrical,alternator+/+generator,2412



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild



Edited 1 time(s). Last edit at 2018-01-13 05:23 PM by TR3driver.

trrdster Avatar
trrdster Wayne Tate
Spencer, NC, USA   USA
Gary, go to the BuckeyeTriumph site and it will explain how to wire in a new one.
Any way to soldier the bad spot?



Wayne
1970 TR6
2000 Jaguar XK8
1949 Triumph Roadster 2000
1978 Spitfire (rust victim)
1971 GT6 (tarp covered for 12 years, rusted inside out)
1980 Spitfire (getting all the good GT6 parts, all poly suspension and Spax shocks)

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ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
Excellent! Thank you! Great information.

I am afraid that I may have been overloading my original Lucas which might be one reason for its failure. I am due for an upgrade. My car has been upgraded with Halogen headlights, air conditioning and heated seats. I have also considered an electric cooling fan upgrade. The additional load probably warrants an upgraded unit rather than a rebuild of a smaller capacity alternator.

ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
In reply to # 1507305 by trrdster Gary, go to the BuckeyeTriumph site and it will explain how to wire in a new one.
Any way to soldier the bad spot?

I don't believe its fixable by soldering. It looks like the broken connection was spot welded. This is probably due to heat. The connection is on one of the diode plates. I doubt that solder would be able to survive the heat.

Gary

ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
In reply to # 1507305 by trrdster Gary, go to the BuckeyeTriumph site and it will explain how to wire in a new one.
Any way to soldier the bad spot?

I am unable to search within the buckeye triumph site to fine the wiring diagram.

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
The actual entire wiring schematic is not in BUCKEYE.
That is in a pdf here:
http://www.advanceautowire.com/schematics.htm



Edited 1 time(s). Last edit at 2018-01-13 06:43 PM by poolboy.

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ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
In reply to # 1507316 by poolboy The actual entire wiring schematic is not in BUCKEYE.
That is in a pdf here:
http://www.advanceautowire.com/schematics.htm

Poolboy. Thanks. I have these schematics. I do appreciate the link though. I have scoured the schematics and cannot find the fourth wire. From 1973 on they show a 3 wire alternator but no 4th wire indicated. I guess I could try and trace the extra wire but it sounds like it feeds back to +12volts.

Gary

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1507321 by ghutch I guess I could try and trace the extra wire but it sounds like it feeds back to +12volts.
That's right. I believe it runs to the same connector in the hot battery cable as the two heavy brown wires do. Logically, it's the same circuit, but what it does is let the voltage regulator (inside the alternator) get a better idea of actual battery voltage without being fooled by the voltage drop in the output wires.

In theory, it should be impossible to overload an alternator, it simply won't put out more current than it can handle. If you draw too much, the battery runs down. But in practice, the Lucas alternators do tend to fail under continuous heavy load. A rebuild might or might not be upgraded to include better diodes etc. than original.

Here is another popular option for an alternator conversion. Bit more work, you'll have to cut and solder wires plus do some simple mechanical work; but the nice thing is that the GM alternator used is very common and easily available almost anywhere. It's also very reliable and should run well over 100,000 miles before it needs attention again.
http://www.mntriumphs.org/aOLD/Tech_Info/Delco_Alternator_Conversion.pdf



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
Thank you everyone. smileys with beer You have been exceedingly helpful. The depth of knowledge here is impressive.

Now off to get this thing repaired and get my TR6 back on the road again. thumbs up

Tommys4 Platinum Member Thomas G
Ojai, Calif., USA   USA
Gary
Just a FYI , BPNW sales a 65amp Lucas alt................

TMG

ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
Thanks Tommy. I did some research and found a company from California that remanufactures what look like Bosch units but boosts them to 95AMP units and drop straight in. It is probably a bit of overkill but as I said I am considering an electric fan upgrade and don't want to be short of capacity.

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
I don't think there's any danger of that...not with 95 amps.
You should get a heavy gauge wire for recharging the battery now, too.

ghutch Avatar
ghutch Gary Hutchison
Apex, NC, USA   USA
1973 Triumph TR6 "Carmine"
I AM CONFUSED!!!!!

I don't understand what is happening!

I have replaced the alternator with a new unit. I have it mechanically installed to be sure that the pulley is aligned and everything is back to the same configuration as my old Lucas.

My original Lucas had the standard 3 wire plug plus a single spade lug. My understanding is that the single spade lug is not necessary if the alternator does not have the additional connection. The unit I purchased does not have a single spade lug so I taped off the additional wire.

I connected the alternator and a digital volt meter. Before starting the engine I charged the battery and was reading 12.4 volts. I started the engine making sure that the alternator was spinning properly. The volt meter showed about 14.6 volts. I operated like this for at least 20 minutes and the car came to operating temperature.

I drove the car around the block but noticed about half way the dash volt meter was reading close to 12 volts. confused smiley By the time I got home it was showing less than 12 volts.

I attached my digital volt meter and the charging system was showing 11.8 volts and no "ignition" or "alternator" light showing on the dash. I shut down the engine and disconnected the 3 wire plug from the alternator and restarted the engine. I measured the output on all three alternator connections and read no voltage at all.

I experienced this same thing several years ago when I attempted to replace the Lucas. At the time I felt that I may have had a defective alternator. Having the EXACT same thing happen again makes me angry. angry smiley

Does anybody have ANY idea what is going on? My original Lucas was functioning perfectly until just recently when the diode plates failed. Connecting a new alternator works for a short period of time and then the new alternator seems to fail and stop charging the system.

Gary



Edited 1 time(s). Last edit at 2018-01-20 09:54 AM by ghutch.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
I had a similar experience a few years ago, with the wife's Toyota. Went through a total of 7 alternators; 6 of them failed in anything from a few minutes to a few days. I went all through the electrical system, looking for a bad connection or loose wire, etc; even replaced the fusible link for the alternator.

But the last time, I did nothing whatever except change the alternator and the last alternator lasted several years (eventually gave the car to my daughter, who traded it in on a Ford).

The parts store where I kept returning alternators (under warranty) didn't even seem very surprised, certainly not upset. Never said a word about anything else wrong with the car, either.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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