Advice on over charging problem . . . . please . . . .

[vickery1971]

Hello, I’m after some advice on an alternator problem on my mk1. I have just noticed that it is over charging, happens on and off, sometimes accompanied by the battery light and a lot of squealing (with new belt nice and tight) I have metered it and I’m getting 15v at idle and 17+ with a bit of gas, it kind of settles after a a few miles but I am aware that ill cook my nice new battery if I keep driving. My question is, could it be the regulator as the alternator has only done about 10k (but is six years old) if so how can I test it? . . . . if not it looks like a new alternator.

Thanks for any help and advice

Ian

[Staggard]

Hello, I’m after some advice on an alternator problem on my mk1. I have just noticed that it is over charging, happens on and off, sometimes accompanied by the battery light and a lot of squealing (with new belt nice and tight) I have metered it and I’m getting 15v at idle and 17+ with a bit of gas, it kind of settles after a a few miles but I am aware that ill cook my nice new battery if I keep driving. My question is, could it be the regulator as the alternator has only done about 10k (but is six years old) if so how can I test it? . . . . if not it looks like a new alternator.

Thanks for any help and advice

Ian

I would have said regulator definatly not controling the output of the alternator How do you test it ? Don't know!! over to the rest of the forum

[Motorcycle mad]

Hi Ian
I have enclosed a basis wiring diagram of the Stag alternator circuit that may help you understand the system better. (I hope you can pick it up?)
I am assuming your car is one that is still fitted with the Lucas 11AC alternator and the separate 4TR regulator. If it is this system it is a fair bet that it is the regulator at fault. The first thing I would do, is check the battery voltage with a dead engine, voltage should be about 12.6 volts. Then run the engine up and allow a few minutes for the alternator to put back into the battery the energy taken out for starting, the only way you can test the system is with a volt meter across the battery, with the engine running at about 2000rpm you should have a voltage reading of between 13.7 and 14.4 volts, if the voltage is way above the higher reading you have a fault which needs investigating. First I would check the negative wire from the alternator brush box (I think that should be the brown and green wire 14/010) to the "F" terminal on regulator to ensure that is not shorting to earth (if it is it will by pass the regulator and cause the alternator to be on full output all the time giving you your problem), this is best done by temporally replacing the wire (just run a loose wire in the engine bay, but keep it away from the fan belt, and fan etc), if the result is the same I would replace the regulator. Another check you could try with a voltmeter across the battery to monitor the voltage is switching the headlamps on full beam, along with the heater motor to maximum, this creates an increase in demand from the battery, which causes the regulator to start functioning correctly again, but long term you will need to change the regulator.

Best of luck
Ken
IMG.pdf

PS sorry picture wrong way up

[V Mad]

Before you buy a new regulator, consider upgrading to the 18ACR alternator which has a built in regulator and does not need a control box either. Much more reliable and more current if you need it. This is a fairly easy modification; just connect the IGN wire and add a large spade connector to double up the connectors on the main lead. I have just converted mine using a proper 3-way alternator connector.

[73stagman]

How do you test it ? Don't know!!

Get a second opinion from a good multi meter. The dash mounted "gauge" probably wont be as accurate as you want it to be. If it is as old as the car it wont be calibrated so is only any good as a "gauge" not a measuring device. I mean that it will tell you the difference between flat, charging and at standby but the voltage measurement wont necessarily be correct. Your "gauge" could be 2 volts out at both ends of your reading and then you wouldnt have a problem (13 volts at idle and 14.4 volts at higher revs would be OK)

[vickery1971]

Hi, thanks for the posts, the two readings (15 and 17+) were taken with a multi meter, i was just wondering if there was anything i could try, maybe cleaning something . . . . . . just cant believe its knackered after less than 10k.

[Staggard]

Hi, thanks for the posts, the two readings (15 and 17+) were taken with a multi meter, i was just wondering if there was anything i could try, maybe cleaning something . . . . . . just cant believe its knackered after less than 10k.

That's the point!! its not if its chucking out that sort of charge the 4TR unit is

[Colonel Mustard]

I would agree with all of the above. The alternator is working fine if it can deliver those kind of outputs. If the wiring is undamaged, you need a new regulator.

My Mk 1 has been modified to take the later type alternator with internal regulator. (It's an easy mod that doesn't cost much...I did the same thing on my '67 Scimitar 3 litre Coupe for reliabilty)

Chris