11 ACR Charging problem?

[MandM]

Hi all my friend has a Mk1 stag with a 11acr alternator, the problem he is having is the above 1700 rpm the charging light is out and charging at 13/14 volts but when the rev's drop below 1700 rpm the light comes on.
What could be the problem, the regulator and or adjustment if possible? or the alternator? or something else?

Thanks for your help

[new to this]

New Alternator needed, one of the diodes is playing up

[MandM]

Thanks Dave

[Phil S]

Thought the 11 acr had an external regulator? The used to be adjustable back in the day

[DJT]

Mk1 Stag was fitted with an 11AC alternator, with external regulator mounted on RH suspension turret. Mk2 Stag was fitted with an 18ACR, with internal regulator and diode pack.

Was there an 11ACR?

[MandM]

That might be me, as I assumed it was an ACR it,s the mk1 with regulator , so can that regulator be adjusted ? or is it a new alternator?

Thanks all for the help

[marshman]

Depends on the regulator. I believe some of the earlier "genuine" regulators had an adjustment screw - usually sealed with wax or similar. Later ones were "fixed" with no adjustment. It is difficult to say exactly what the problem is with out some diagnostic checks on the alternator output. As Dave (newtothis) says it could be a diode in the rectifier which is in the alternator.

If it were my car I would first examine the 4TR regulator and look for signs of heat damage/burning. If none then suspect the rectifier in the alternator. I would repair the existing alternator rather than replace with a "recon" or "new" one, likely to be much more reliable. I think the rectifier "pack" consists of 6 individual diodes mounted on a circular plate. It should be possible to remove the pack and test each diode individually to confirm that this is the problem - unfortunately due to the way they are constructed I don't think it a simple task to replace a single diode as it was on some alternators.

Here is a link to a Lucas Service Manual which covers the 11AC. It has details of how to test etc. Just depends how much time you are willing to spend on it.

https://www.lrsoc.com/forum/forum_fi...ual%20A1-5.pdf

This covers the early version of the 11AC which required an external relay. I think - but not sure - later ones as fitted to the Stag - had some extra diodes to isolate the regulator which did away with the need for a separate relay. However the basic principles and testing of the rectifier "pack" will be the same.