Charging light doing strange things

[Allan NZ P5b]

Today at 70mph down the motorway suddenly and briefly the ignition light came on. It then went off again 3-4 seconds latter.
It did it again at about 1400 revs also for a few seconds.
When testing charge to battery all is fine 13.8 volts
Light would occasionally flicker at lights in past when revs too low to trigger field current. But otherwise never done this before,
since this episode I have driven about 90 minutes in total and all seems normal,
Amp meter seems same as usual.
Any clues as to what I tell the sparky if it happens again.
About a year ago I have the charging circuits checked by an autosparky who does a lot of and owns several British classics he advised all was fine and light glimmering at low revs was not unexpected.

Regards

[Deleted]

Ignition Light glimmering at very low revs is OK - coming on at higher revs points to worn/dirty brushes, faulty warning light can, field isolating relay or regulator in that order.

This asuumes all connections and wiring are good

[PatMcCoy]

Have you had the dash pod out
Might have a loose wire
Pat

[Allan NZ P5b]

Yes pod has been out but conections to ignition light at bulb end are all fine and havent disturbed other end but will check again when I put rev counter back in. Seems to be behaving now, just got in after a trip 20mins each way.
will consult diagrame and see if any conections could have been disturbed.

Thanks for tips Torsion Bar & Pat

Regards

[Allan NZ P5b]

This earlier problem seems to have settled down, until today. I never did find a cause but it happened so rarely and for such brief periods of time that I ceased to worry about it until today. The light came on and stayed on. Regardless of revs. Where should I look first? Bearing in mind this has been a minor intermittent problem 8 months ago.
I have a spares car so can change/swap components so would like to start with easiest first.
Also please note I will be away for 5-7 days going up to Fiji to help sail a 105 foot boat back to New Zealand as part of my therapy.

Regards

[Phil Nottingham]

???Actually the very same happened to me during our Ireland tour last June - it first came on after about a 100 miles high speed touring whilst still in England as it was still charging I ignored it and it went off again after 1/2 hour or so and stayed that way until after a days touring in Ireland a week later - it was hot eather again. Went off and has behaved ever since!!

I checked all the wiring but alos carry a spare Warning light can just in case it was this - it is us
usually one of the alternator brushes sticking and one always wears out twice as fast - these were OK though

WEired

[stantondavies]

I take it that the problem didn't happen in very wet weather when water on the fanbelt can on occasions cause it to slip, giving a momentary red light.

[Deleted]

allannz said:

Today at 70mph down the motorway suddenly and briefly the ignition light came on. It then went off again 3-4 seconds latter.
It did it again at about 1400 revs also for a few seconds.
When testing charge to battery all is fine 13.8 volts
Light would occasionally flicker at lights in past when revs too low to trigger field current. But otherwise never done this before,
since this episode I have driven about 90 minutes in total and all seems normal,
Amp meter seems same as usual.
Any clues as to what I tell the sparky if it happens again.
About a year ago I have the charging circuits checked by an autosparky who does a lot of and owns several British classics he advised all was fine and light glimmering at low revs was not unexpected.

Regards

[Deleted]

Sorry about the last reply as i have never been on a board before.
A strong likelihood is the brushes or brush springs, if they are badly worn they will bounce at higher revs (speeds).
? does the amp meter fluctuate at the same time as this will help in troubleshooting the fault.
Regards Neil.

[Allan NZ P5b]

Hi all thanks for the suggestions.
Just got back from sailing the pacific and now the car battery has gone flat due to running it home with out it charging. Will put it on charge tonight and swap the alternator from my donor car and see if problem goes away. Will advise.

Boy is the pacific big, really big, you have no idea how very big it is, till you are half way between Fiji and New Zealand traveling at 7 knots in 4 meter swells and 35 knots of wind on the nose.

Then you wish it were not quite so big

Regards Allan

[Allan NZ P5b]

OK I have swapped the warning light control can no change.
swapped the regulator no change
swapped alternators all good charging well ;D
swapped control can and regulator back all still good ;D

so I guess the problem is the brushes.
I wish to replace the brushes on the original alternator clean it up and reinstall as the donor alternator is very tatty looking and the original is quite tidy and will be more so when I have finished I appears from the manual that the brush box assembly can be removed with out disassembling the alternator is this correct
Are the brushes easy to get replacements
Is this all I should do at this stage or should I send it to an auto sparky for a complete overhaul. do other bits fail often

Regards

[Deleted]

Hi Allan

I would have it professionally overhauled, that way you get a warranty too!!

Have you considered the Ford Orion alternator upgrade - detailed elsewhere on this site?

CHeers

Adrian

[Allan NZ P5b]

I decided to take your advice Adrian and put my alternator into the shop for a full rebuild came back with the case polished and rest repainted shinny black with new bearings, brushes diodes and slip rings etc only cost $180.00 NZ so was very happy and now it whacks out much more voltage and amps apparently it was not in good shape so exercise was very worth while thanks for all the advise.
Car is going back to shop tomorrow to have an electric fan fitted. The radiator is good and block and associated plumbing in great order but here in NZ the temp is often high over summer and the traffic in the city where I live is heavy at peak hour and while I rarely travel in it last summer on a few occasions I was starting to get concerned when trapped in non moving traffic temp gauge went above 1/2 way and as it normally runs in first 1/4 of gauge this made my stress levels run high also so have decided to fit a fan as car is my daily drive and I don't want to risk cooking the engine

Regards

[Deleted]

Hi Allan
Glad the alternator overhaul proved to be sucessful, and it looks good too!
I put a Pacet 16" 'blower' fan unit on the front of my radiator, controlled by an adjustable thermostat.
Then I removed the engine driven fan and rely purely on the electric fan. Works very well, quieter and very effective.
Well done, Allan, welcome to the Non-Standard Rover club. I should send you a 'MAGPIE' sticker!!

Regards

Adrian

[Allan NZ P5b]

Just picked up the car from the sparky with the new fan drove back in very hot weather and deliberately chose the congested route at peak hour to find heavy traffic and I did. Temp stayed just below normal and fan kicked in. Quiet! you can't here it. I had to get out and look to confirm it was running. Very happy fitted a 16" fan with a temperature adjustable sensor so now will feel safe in traffic

Regards

[Allan NZ P5b]

It has started again the charging light came on for a few seconds then went off again then came on for about 6 minutes. When I got home I started car again and light was on then went off as I started to check with a multimeter.
I have it charging at 13.3 volts when engine at 1000rpm.
Amp meter shows that it seams all OK moves up just after start for a few seconds then settles on a little 1-2mm above 0 it flickers up when you turn on lights etc
What is the most likely cause as Alternator has just been rebuilt and appears to be charging?
What controls the charging light?


Thanks in advance

[Deleted]

Allan
In the engine bay, to the left of the fuse box, you will find a flat device and a cylindrical device. These may be the alternator regulator (flat device) and the alternator warning light control unit (cylindrical unit).
Might be a good idea to check the terminal connections are sound and secure.
If the charging is OK, then I would suspect the warning light control unit and change it. This is a very common device used on MG's, Rovers, Aston Martins and others.
Keep up the good work Allan.

Regards

Adrian

[dorsetflyer]

Allan, the unit you are looking for is model 3AW. It is marked on it.
According to the manual you can bench test these to see if they are at fault or not.
But check for dirty and /or loose contacts first.

[Phil Nottingham]

As it seems you have tried all the obvious it ould be awiring fault like a high resistance joint. I would rewire the warnig light cisrcuit - its dead easy

[lagain]

I would suspect the 4TR unit, which is the flat red unit near the fuse box.
The 3AW unit is the silver cylinder that looks like a flasher unit, all this does is control the warning light , the feed is the single post on the rear of the alternator and should be 7.5 volts.
I had my alternator repaired last year and the auto electrician told me that there are 3 different stators available for this unit, depending on what car it was fitted to. The stator is the winding that does not move. The books do not say which stator should be fitted to the alternator of a P5, so you need an old auto electrician with a good memory !

[dorsetflyer]

The stator is probably the most reliable part of an alternator with its' thick copper windings.
Rotors do fail occaisonally but its' suually because the copper segments wear right down, and then there is no separating gap. Debris from a worn rotor can short out the gaps.

If the 4TR unit is suspect, then again the manual gives instructions on how to test them.