TR6 TR6 Alternator/Fan Belt Issues

[MarkT]

Ok, after finishing the front suspension, I took the car out for a drive. After about 15 minutes, I start to smell smoke and see smoke coming out of the left side of the bonnet - I figure some wire smoke and pull over to check...

Indicators and horn don't work, so I reckon its that fuse system. After limping slowly home (no more smoke) and noticing that the red ignition warning light is on and the volt-meter is showing a slow decrease, I decided it could be an alternator problem. The indicators and horn work again after re-seating the fuse (it didn't blow), although the indicators don't flash, just stay constantly lit - maybe the flasher unit. The alternator belt was pretty shot, and came off on testing at home.

So, I've just been to AutoZone to get a new fan belt (and fire extinguisher!). They sold me a Duralast cogged V-Belt (part # 15445) which is 1.1 cm wide and 1.1 m long. After fitting the new belt and tightening it so there is around 0.85-0.9" play, I start the car....now I have the following symptoms: squealing (I guess indicates that the fan belt is loose) and a burning smell plus a lot of smoke. I'm 95% certain that the smoke is from the belt and not the alternator - it also comes from the other pulley areas. So - did I get sold the wrong belt? Is it too loose? Can anyone recommend a good off-the-shelf belt?

FYI I have a 1976 non-PI TR6 with a Lucas alternator and looking for the alternator-water pump belt.

Thanks,
Mark

 

[Dave Russell]

Hi Mark,
The belt tension is a little light but shouldn't cause such a severe problem as you describe. You could tighten it & see what happens. How does the new belt width compare to the old belt. A correct belt should not ride in the bottom of the pulley grooves but more up on the sides.

If the belt appears to fit correctly, I'm not sure what devices the belt drives on your car, but it's possible that one of them is bound up which causes the belt to slip. Check the alternator for bad bearings, waterpump if on the same belt, & anything else that is driven by that belt. I think that "something" might be causing more than normal resistance to turning.
D

 

[MarkT]

Dave,

After doing a bit of searching, it seems that the width of the new belt is a little bit narrow - I think late model 6s need a 1/2" belt, not a shade over 3/8" (the pully width at the top is 1/2"). BUT the new belt is the same width as the old one - so maybe that was off too. I think I'll give a 1/2" a go before moving on to the next stage of the diagnosis....

Mark

 

[Dave Russell]

Good idea. The belt should be wide enough that it rides on the groove sides. Likely the belt top should project above the pulley groove top a bit. It would certainly be the easiest fix. Let's hope so.
D

 

[MarkT]

I got the 1/2" belt; now all it needs is fitting, which will likely cause some trauma all in itself. I figure the 3/8" was put on by a PO as it will easily (or, with a litle prodding) slip over and under all the obstructions to get it into position, whereas with this one something will have to be moved.

One final question - should I be able to turn the alternator pulley freely? At the moment it turns either way about 1/8 of a turn before getting tight.

M

 

[Dave Russell]

Yes, it should turn freely. It should actually spin for a bit if you give it a good twist. The only friction should be from the brushes against the slip rings which is very little. This may be part of the problem. I would investigate further.
D

 

[Alan_Myers]

Hi Mark,

It would be very odd for a belt to start smoking unless something isn't spinning freely and the belt is slipping quite a bit on one of the pulleys. You might also check that the water pump (and anything else using the belt) turns freely when the belt is removed.

Sounds like a bearing problem, or bad brushes in the alternator, if it doesn't spin freely by hand. However, there are a couple things to consider.

It's not uncommon for Lucas those alternators to start over-charging. I'm not sure if it's the built-in voltage regulators or something else that goes out, and well over 20 volts start flowing. That could explain smoke and blown fuses elsewhere in the electrical system. Most any auto parts store can test any alternator if you remove it and take it to them. However, I agree it should spin freely.

If it's a bad alternator, you have some choices.

A lot of people install GM/Delco alternators in TR6 for a more reliable unit. If you'd prefer to stick with Lucas, I'd recommend trying to find a local rebuilder, because that will likely cost less than ordering a Lucas alternator from elsewhere and you can talk with them and see if they have any ideas for improvement.

Let us know what you find.

 

[MarkT]

It turns out that the alternator was completely seized. I've used this as an opportunity(!) to upgrade to a more powerful alternator (in part as I want to do a light upgrade) - I've just acquired the Bosch 55A from a '79 Fiesta. Initial comparison to the dimensions of the 18ACR unit reveal it is a straight swap with no modification, and the old connector even fits. So now I have two more questions:

1) Should I worry about the pulley having a smaller diameter than the Lucas unit (2 11/16" vs 2 7/8")? In my simplistic worldview, a smaller pulley would make it spin faster...

2) Wiring the thing. The stock multi-wire connector from the Lucas unit fits; this has a thick (3 gauge?) brown wire that appears to run directly to the battery positive, and a thinner brown/yellow that would go to the warning lamp. I've seen recommendations to run a 10 guage wire from the spare slot on the alternator B+ multi-connector to the battery connection on the starter solenoid, but I have a pertonix electronic starter; would it be just as well to run this extra wire directly to the battery positive? I guess having two wires going there would spread the load sufficiently.

Cheers,
Mark

 

[Alan_Myers]

Hi Mark,

Good! That sounds like a pretty easily fixed problem. You should be back on the road in no time.

Regarding the pulley size...

No, the slightly smaller pulley shouldn't be any problem so long as you can still adjust the belt properly. You might want to change that belt, too, if you haven't already. The old one probably has some damage due to the friction when the alternator froze up.

In case you don't know, try not to overtighten the belt. That's hard on alternator/water pump bearings. Make it just tight enough to prevent slipping and be sure recheck it after the first 100 miles or so since they tend to stretch a bit initially.

A smaller pulley would only be of concern if it were *a lot* smaller and/or you planned to frequently and consistently run the car at high rpms, i.e. race revs in the 6000+ range. In those cases, a larger "under-drive" pulley would be a good idea. Those are available and can usually be pretty easily swapped.

Regarding the wiring...

Your 18 ACR probably put out around 45-50 amps when it was new. In all likelihood, the wiring is probably up to the 55-65 amps likely from the Bosch. However, it wouldn't hurt to run another wire in parallel to the main wire, just to carry some of the load. Do that if you wish and I'd just suggest the second wire be about the same size as the first. I think the concern about wiring is mostly for earlier cars that had lower output alternators, or much lower output generators, and were fitted with wiring that was just adequate for the loads of those original alternators and generators. In those cases, upgraded wiring is probably more important than on your car.

What are you going to do with the old Lucas 18 ACR? It sounds like you didn't turn it in as a "core". You could get it rebuilt, keeping it as a spare and with the car in case you ever have originality concerns. I think Lucas alts are a bit harder to find in the U.S., but I really haven't checked around for that model. If you intend to just toss it, please let me know before you do. I might be interested in it.

Cheers!

 

[MarkT]

Finally, the new alternator is fitted. I did the new wiring, running a 10 gauge wire (as opposed to a ?8) from the spare b-post directly to battery positive.

I did have one "what have I done!?" moment...I assumed the alternator was a straight drop-in, but it was actually a mirror-image of the Lucas unit. So, cribbing some tips from Bob Danielson's website (https://tr6.danielsonfamily.org/) I aquired a mount bracket for a pre-'74 vehicle and, as they say, Bob's yer uncle and Fanny's yer aunt. There's not much play on the adjustment bracket, so I'll have to manufacture another one of those at some point.... Now the volt-metre reads a constant 14 and a bit volts at idle, instead of the all-of-the-way-in-the-red of the Lucas. Nice.

Alan - I'll give it some time to check the alternator works properly and I don't torch anything else. After that, you're welcome to the old Lucas unit....

Cheers,
Mark