Last year in July I changed the alternator with a new one on my 1850.
Recently the voltage gauge catches my eye. Directly after starting the voltage gauge takes some time to raise to a healthy 13 Volts. After a couple of miles it catches up. It's not just the gauge, the OD can't be switched on until the voltage reached the desired values. When I've to stop during the trip, say at traffic lights, the reading drops again and sticks at 10~11 Volts.
Can someone point me in the right direction: what does this mean, what's on its way out?
Slow / low voltage reading
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Edin Dundee
Re: Slow / low voltage reading
They might not be related.....
Bit of a pain, but....
Carry a meter.
On start-up measure the volts across the battery.
A couple of miles later, same again, you get the picture.
I would think 13 volts is too low, but don't trust the car's voltmeter.
The overdrive might just need the oil to heat up.....
Bit of a pain, but....
Carry a meter.
On start-up measure the volts across the battery.
A couple of miles later, same again, you get the picture.
I would think 13 volts is too low, but don't trust the car's voltmeter.
The overdrive might just need the oil to heat up.....
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Toledo Man
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Re: Slow / low voltage reading
I second what Bill said about not trusting the in-car voltmeter. Better to measure the voltage across the battery terminals with a multimeter for a more accurate reading.
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West Yorkshire Area Organiser
Meetings take place on the first Wednesday of the month at 8.00pm at The Railway, 1 Birstall Lane, Drighlington, Bradford, BD11 1JJ
2003 Volvo XC90 D5 SE (PX53 OVZ - The daily driver)
2009 Mercedes-Benz W204 C200 CDI Sport (BJ58 NCV - The 2nd car)
1991 Toyota Celica GT (J481 ONB - a project car)
Former stable of SAY 414M (1974 Toledo), GRH 244D (1966 1300fwd), CDB 324L (1973 1500fwd), GGN 573J (1971 1500fwd), DCP 625S (1977 Dolomite 1300) & LCG 367N (1975 Dolomite Sprint), NYE 751L (1972 Dolomite 1850 auto) plus 5 Acclaims and that's just the Triumphs!
Check my blog at http://triumphtoledo.blogspot.com
My YouTube Channel with a bit of Dolomite content.
"There is only one way to avoid criticsm: Do nothing, say nothing and BE nothing." Aristotle
Re: Slow / low voltage reading
Alright, I measured the battery poles:
engine off: 12,4 V
engine just started, idling with choke so about 1500 rpm: 12,5 V
engine a bit revved, 2500 rpm: 12,5 V
engine revved a bit more. 3000 rpm: 14,5 V
back on choke idling: 14,5 V
idling, 800 rpm: 14,5 V
So it takes a while to climb up. When the 14,5 V is reached it stays there, even when rpm's are dropping.
(although I had a trip last week where the voltage dropped after some minutes idling, when I was out of the car)
In car voltmeter seems inaccurate regarding actual values, but is following the increase or decrease in voltage.
What does these symptoms tell?
engine off: 12,4 V
engine just started, idling with choke so about 1500 rpm: 12,5 V
engine a bit revved, 2500 rpm: 12,5 V
engine revved a bit more. 3000 rpm: 14,5 V
back on choke idling: 14,5 V
idling, 800 rpm: 14,5 V
So it takes a while to climb up. When the 14,5 V is reached it stays there, even when rpm's are dropping.
(although I had a trip last week where the voltage dropped after some minutes idling, when I was out of the car)
In car voltmeter seems inaccurate regarding actual values, but is following the increase or decrease in voltage.
What does these symptoms tell?
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AlanH
Re: Slow / low voltage reading
Could be a problem with the machine sensing.
I think Jon had something similar.
I think Jon had something similar.
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Mad Mart
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Re: Slow / low voltage reading
Engine not running you should have 12.6V, so 12.4V is a bit low. As far as I know you should have the 14.5V (or there abouts) even at idle.
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Edin Dundee
Re: Slow / low voltage reading
Alternators shouldn't be idle/rev sensitive, something's not right. 14.5 volts ish all the time, irrespective of engine speed. Dodgy alternator is my guess, possibly the regulator knackered? Or sticking/worn brushes?
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Jon Tilson
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Re: Slow / low voltage reading
Its lost the sensing bit so wakes up at 3000 rpm.
Mine was the same. Its one of the diodes that's blown....
I had a spare so swapped it...problem solved.
There is a lot on youtube that shows how to change lucas acr regulators etc...
Jonners
Mine was the same. Its one of the diodes that's blown....
I had a spare so swapped it...problem solved.
There is a lot on youtube that shows how to change lucas acr regulators etc...
Jonners
Note from Admin: sadly Jon passed away in February 2018 but his humour and wealth of knowledge will be fondly remembered by all. RIP Jonners.
Re: Slow / low voltage reading
Thanks guys, I'll check it later this week.
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MIG Wielder
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Re: Slow / low voltage reading
Hello Henk, Sorry about the late reply and it was jolly good meeting up at Stoneleigh may I say ! ( I was the one with the MGB btw.).
There is one other possibility for the slow increase of voltage. Is the ignition warning light working O.K. or has it been swapped for a low-current LED bulb ?
The reason this will give a slow increase of alternator voltage is that the current that flows through the ignition warning light provides some initial alternator field current during start-up. If this current isn't present then the alternator relies on the residual magnetic field in the field winding to get the current flowing. Which can take some time to establish itself.
There is a useful circuit diagram on page 86-11 of the Sprint workshop manual that explains this.
HTH.
Cheers for now,
Tony.
There is one other possibility for the slow increase of voltage. Is the ignition warning light working O.K. or has it been swapped for a low-current LED bulb ?
The reason this will give a slow increase of alternator voltage is that the current that flows through the ignition warning light provides some initial alternator field current during start-up. If this current isn't present then the alternator relies on the residual magnetic field in the field winding to get the current flowing. Which can take some time to establish itself.
There is a useful circuit diagram on page 86-11 of the Sprint workshop manual that explains this.
HTH.
Cheers for now,
Tony.