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Alternator upgrade

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bikeboy Avatar
bikeboy Silver Member Ian Fox
Lara, Victoria, Australia   AUS
I've ordered a 70Amp alternator as an upgrade primarily because the thermo fan I've fitted seems to draw a lot of current and is a drain that wasn't there initially. I've also now got Halogen headlights, which is another additional load. My question is can I keep the stock Ammeter as it's installed, or should I look at a voltmeter, assuming I can find one to match my other gauges? Will it put the original gauge under too much stress and jeopardise the harness? I know I can by-pass the gauge and join the wires together, but I'd eventually like to know what's going on.

cheers
ian

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Reddragon Avatar
Reddragon Dale M
Chesapeake, VA, USA   USA
1963 Triumph TR4 "Road Runner"
1974 Triumph TR6 "Tweety"
Ian

I'm lazy today or I would do the search for you. There was a post not to long ago on alternator upgrades and how to use a a wire on the ammeter to register it correctly with a high amp alternator. Do a search for TR3driver and see what you come up with.


#7 in this post https://www.triumphexp.com/phorum/read.php?2,1587099,1587176#msg-1587176

Red



Edited 1 time(s). Last edit at 2019-01-08 07:07 AM by Reddragon.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
When I converted my TR3 to an alternator keeping the original ammeter in place, I discovered that after a few weeks the ammeter needle started to stick at the +30 stop, probably from being banged against it every time the engine started. I didn't wait for the movement to stop working entirely, but I believe it would have eventually. I don't know that a TR6 ammeter would suffer the same fate, but it seems likely.

My solution, which worked great for many years, was to add a short length of wire to the back of the ammeter, to divert part of the current. Effectively making it a 60-0-60 ammeter instead of 30-0-30.


Takes a bit of experimentation to find the right length of wire, but not too bad. Flip on the headlights without the shunt and note the needle position; then add the shunt, turn the lights back on and check again. If the reading is half (or whatever ratio you choose), you've got it.

Another solution is an aftermarket ammeter. The hole is a very standard size, any 2" gauge will fit.



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

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dk pony Avatar
dk pony David C
MT Carmel, TN, USA   USA
1972 Triumph TR6 "Melvin"
LFMTR4 Avatar
LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
I went with a Smiths voltmeter when I converted to a 57A. You should run another 8 gauge wire in parallel from the alternator to the battery or starter as the extra current will over power the current wire when the battery needs to be fully charged if it goes flat. Remember that is an unfused section of the loom so not a good place for a over current meltdown.

bikeboy Avatar
bikeboy Silver Member Ian Fox
Lara, Victoria, Australia   AUS
In reply to # 1588099 by TR3driver Takes a bit of experimentation to find the right length of wire, but not too bad. Flip on the headlights without the shunt and note the needle position; then add the shunt, turn the lights back on and check again. If the reading is half (or whatever ratio you choose), you've got it.

Hi Randall. Does that shunt wire get hot at all? Is that something I'd need to watch?

cheers

gbtr6 Avatar
gbtr6 Perry Rondou
Titletown, WI, USA   USA
I put the newer Bosch alternator from a Ford Fiesta on, I think @ 65 amps, and didn't change a thing. All is good.

Perry

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1588176 by bikeboy Hi Randall. Does that shunt wire get hot at all? Is that something I'd need to watch?
A bit warm perhaps, if your battery was way down. But not what I would call hot at all. The inside of the ammeter will dissipate the same power, with less cooling, so it will get warmer than the shunt does.

No need to watch it, IMO.



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

LFMTR4 Avatar
LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
In reply to # 1588181 by gbtr6 I put the newer Bosch alternator from a Ford Fiesta on, I think @ 65 amps, and didn't change a thing. All is good.

Perry

And it will be until one dark, rainy, cold night when you have the wipers, lights and blower on and that new alternator tries to send all that amperage down a 45 year old 8 gauge wire with oxidized connectors. BUHA HA..

Seriously, if the car ever demands 65A for a few minutes say to charge a depleted battery you could melt the insulation off the brown wire and ground it with no fuse. Could start a fire. I ran a second parallel wire but hey, it’s your car.

nync Avatar
nync Glenn Meteer
Charlotte, NC, USA   USA
Lou, I have also upgrade the alternator on the '69 TR6. Would an additional 8 or 10 guage wire be proper to run it directly from the alternator to the battery? This is the alternator, with the original Lucas black plastic back fitted


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LFMTR4 Avatar
LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
In reply to # 1590163 by nync Lou, I have also upgrade the alternator on the '69 TR6. Would an additional 8 or 10 guage wire be proper to run it directly from the alternator to the battery? This is the alternator, with the original Lucas black plastic back fitted

Glenn,

What is the amperage output of that alternator? If it’s under 60A, you should be ok with the stick set up. Over that, I would add the parallel wire as insurance.

nync Avatar
nync Glenn Meteer
Charlotte, NC, USA   USA
Lou, thanks for the reply. The new unit is 95 amps. Do you recommend a 8 ga wire direct from the alternator to the battery positive post instead of to the ampmeter and starter? It would sure be a lot easier going direct. Glenn

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
If you do that, the ammeter will no longer read correctly. It will likely show discharge even when the battery is not being discharged, because now it will show at least most of the alternator output going to the car as discharge.

However, I don't think the stock ammeter is going to like that much current either!



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

LFMTR4 Avatar
LFMTR4 Lou Mijares
Scottsboro, AL, USA   USA
The stock ammeter will not read correctly anyway, it’s calibrated to the stock alternator. You could shunt it but it’s tricky and I’ve never cared for that much current going though one place behind the dash. When I upgraded my alternator, I swapped the ammeter to a period correct Smiths voltmeter off eBay. Cost me $25.

To answer your question, yes I would run an 8 gauge wire from the alternator to the battery terminal. The biggest potential load is a discharged battery making that alternator put out so I would put the wire between them.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1590321 by LFMTR4 The stock ammeter will not read correctly anyway, it’s calibrated to the stock alternator.

Actually, it will be accurate (without the added wire) as long as the charging current is within it's range. Which will be 90+ percent of the time.

It's sized to the original alternator (more or less), but in no way "calibrated" to it.



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

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