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voltage gauge question

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voltage gauge question
#1
  This topic is about my 1978 Triumph TR8
uspsmech Avatar
uspsmech Jim F
North Providence, RI, USA   USA
1978 Triumph TR8 "007"
Looking for advice or opinion on a minor issue I've never noticed before
Started my 1978 TR8 with stock Lucas alternator and original voltage gauge today
I noticed at startup the ignition light was on and voltage needle at extreme left of gauge
It took roughly twenty seconds for the needle to get into what I consider a normal range,( the light went off almost instantly after startup)
At the battery I have 12.75 volts at idle, unfortunately nobody around to rev the motor while I check meter
Am I looking at a problem or is this lazy needle just something I've never noticed before?
I did remove the ground from alternator bracket to shock tower and clean all contact points thinking it could be a weak ground
That really had no effect
Thanks for any opinions or advice,
Jim



" Enjoy the Drive", Jim

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darrellwalker Darrell Walker
Vancouver, WA, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
My needle is also lazy, and I've been told that is normal. I don't know why Triumph decided to heavily dampen the motion of the volts gauge, while having the fuel level and water temp be super responsive.



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA

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uspsmech Avatar
uspsmech Jim F
North Providence, RI, USA   USA
1978 Triumph TR8 "007"
Thanks Darrell, that makes me feel somewhat better. Spend my time fixing problems that are actual problems



" Enjoy the Drive", Jim

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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, OR, USA   USA
1980 Triumph TR7 Drophead "The Great Pumpkin"
1980 Triumph TR8 "Wedgie"
In reply to # 1601655 by darrellwalker My needle is also lazy, and I've been told that is normal. I don't know why Triumph decided to heavily dampen the motion of the volts gauge, while having the fuel level and water temp be super responsive.

The voltage gauge is thermal, not electromagnetic. So it takes a few seconds to reach equilibrium. This is done to reduce noise sensitivity. The temperature gauge is similar in its operation.

Vance



1980 Platinum Metallic TR8, frame off restoration, complete.
1980 Vermilion TR7 Sprint replica, in progress.

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darrellwalker Darrell Walker
Vancouver, WA, USA   USA
1966 Triumph TR4A "Christy"
1981 Triumph TR8 "Kate"
In reply to # 1601731 by Darth V8R
The voltage gauge is thermal, not electromagnetic. So it takes a few seconds to reach equilibrium. This is done to reduce noise sensitivity. The temperature gauge is similar in its operation.

Hi Vance,

I agree the volts gauge is thermal (bi-metallic strip). But the fuel level and temp gauge are both electromagnetic. If they were bi-metallic, then they would need a voltage stabilizer like the TR4A (and I think TR6). The volts gauge of course doesn't need stable voltage since it is measuring voltage.

Volts gauge on the top, fuel level and temp on the bottom.



Darrell Walker
66 TR4A IRS-SC CTC67956L
81 TR8 SATPZ458XBA406206
Vancouver, WA, USA


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Darth V8R Avatar
Darth V8R Vance Navarrette
Beaverton, OR, USA   USA
1980 Triumph TR7 Drophead "The Great Pumpkin"
1980 Triumph TR8 "Wedgie"
In reply to # 1601824 by darrellwalker
In reply to # 1601731 by Darth V8R
The voltage gauge is thermal, not electromagnetic. So it takes a few seconds to reach equilibrium. This is done to reduce noise sensitivity. The temperature gauge is similar in its operation.

Hi Vance,

I agree the volts gauge is thermal (bi-metallic strip). But the fuel level and temp gauge are both electromagnetic. If they were bi-metallic, then they would need a voltage stabilizer like the TR4A (and I think TR6). The volts gauge of course doesn't need stable voltage since it is measuring voltage.

Volts gauge on the top, fuel level and temp on the bottom.

Darrell:

All the gauges except Oil Pressure are thermal in the TR6. I ASSUMED (and we know what means) that the TR7 was the same.

Another perfectly perfectly reasonable assumption blown to hell by data. I hate it when that happens! angry smiley

Vance



1980 Platinum Metallic TR8, frame off restoration, complete.
1980 Vermilion TR7 Sprint replica, in progress.

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TR8Craig Craig B
Johnstown, PA, USA   USA
At idle shouldn’t the battery voltage be about 14 volts? The 12.75 seems low to me.

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uspsmech Avatar
uspsmech Jim F
North Providence, RI, USA   USA
1978 Triumph TR8 "007"
Actually had time today to revisit the "non" problem today.. With car off, battery measures 12.01 volts. After initial startup, fast idle, measured 13.5 volts. At 2000 rpm, 14.11 volts. Fully warmed up, slow idle 12.85 volts. The needle on the gauge seems much less lethargic with the warmer weather. Now if only I could fix the elusive oil leak as easily! Thanks to all for the help and or advice,Jim



" Enjoy the Drive", Jim

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TR8Craig Craig B
Johnstown, PA, USA   USA
Guess I need to check my Triumph. Memory tells me my MG battery voltage is about 12 with engine off and 14 at idle. Hopefully Lucas isn’t playing with me.

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