Is my Alternator on the way out

[Derbyman]

Now the nights are darker I have spotted that the red ignition light glows very dimly when I have the fan on. When I turn the fan off it goes out, the intensity of the glow gets brighter if I put the fan on fast and goes dimmer when I put it on slow. Is this a wiring problem or is the alternator on its way out and not charging the battery?

Would like to resolve the problem as I use the car everyday and really need the blower.

[222s]

Assuming that you have the standard 35A alternator, then those symptoms are normal.

For more info, have a read of Ron Kwas' excellent write-up about the behaviour of the amp light:
http://www.sw-em.com/AMP_Indicator_ON.htm

[Ron Kwas]

Derbyman;

The article is particularly applicable to Generator (Dynamo) equipped 544/122/1800 vehicles, and I am not able to see what kind of vehicle you have, but have a read anyway...

222s; Tnx for reference!

Cheers from Connecticut!

[Derek UK]

The behaviour of your red light is certainly typical of dynamo equipped cars due to how the Bosch charging system works but I'm not so sure that alternator cars would have the same problem. Good idea to have a critical check on the fuse box, fan belt adjustment, and all of the earthing points, Starter motor connections and battery terminals should also be clean and tight.

[Underdrive]

Alternators when working correctly will switch the charge light either on or off not 'somewhere in between' like a dynamo when the revs drop down low and particularly under higher load. Chances are that the alternator brushes are at the end of their life and can easily be checked and replaced cheaply.

[P1800Ray]

My red light stays on for a while (5 minutes) when starting my P1800 (1962) and then goes off.

Is that an alternator issue ?

[Ron Kwas]

Ray;

..again, you must specify Alt or Gen when looking for advice! Symptoms are different for the so equipped systems.

...if unmodified Gen is installed and those are your symptoms, it suggests Brushes are very worn, therefore have low pressure onto the Commutator, and are not cutting through the film there until a after a while engine has been running.

I'd order some new Brushes and have them ready to go for next time the Gen is removed...then lightly burnish Commutator surface to clean before installing new Brushes...

Also, if an unmodified Gen system, have a helper keep an eye on the AMP Indicator just after starting (and Indicator is ON, even with raised idle to around 1500RPM), using a test wire, momentarily connect Df terminal of Gen to chassis, bypassing Charging Regulator and making Field current...if Indicator persists, Charging Regulator is suspect in that it is not making this connection, but if Indicator extinguishes, it rather confirms the worn Brushes condition. Remember the Charging Regulator enables Field current by tying Df Terminal to chassis.


From: http://www.sw-em.com/AMP_Indicator_ON.htm

Cheers from Connecticut!

[P1800Ray]

Thanks Ron, are the brushes still available or is it a case of replacing the whole unit ?

PS - sorry for thread hijack !

[Derek UK]

Unless its been converted the '62 1800 would have a dynamo. Brushes for the dynamo are available from Brookhouse. Dynamo obviously has to come apart and you may need a heavy duty soldering iron to remove the old and fit the new brushes. Economical, £10 and a couple of hours DIY.
If you have an alternator it will depend on what it is with regard to replacement parts. Have a look here http://www.jcrsupplies.co.uk/product..._REBUILD_PARTS

[Ron Kwas]

Forum;

Suggested viewing: A good qualitative explanation of operation of a Shunt Generator: https://www.youtube.com/watch?v=HWDSdJKZ9fY

Enjoy!