Odd Ignition fault

[andy thompson]

Ignition light on my Stag comes on only when you turn the ignition off ie completely off and accessory position.

Just started doing it... is parked in the drive with the light on  

Volts are fine (14v) ie charging .. whilst driving but ignition light goes off when you turn the ignition on...

Must be simple but its got me confused

ideas???

[Spitfire2500]

Maybe nothing to do with it but I had a similar sort of problem recently with the Land Rover. Turned out to be a blown diode in the alternator's rectifier pack the end result of which was a constant 4A draw from the battery when the engine wasn't running (with the obvious results).

But with only one diode (out of six) gone the correct DC charging voltage was maintained when the engine was running which confused me for ages until I flipped the multimeter to AC and measured 30V AC imposed on the DC and twigged immediately what was going on.

Anyway, enough waffling, sounds like an alternator- or wiring-related problem to me but I am oftem wrong.

[andy thompson]

Bound to be a flipping blown diode or similar ... guess I'll find out if its a 4A drain tomorrow morning when i go to start the car  >:(

[sparky_spit]

I think you can prove this by pulling the small wire off the back of the alternator. Might be be tricky if you have a moulded connector, because you need to keep the 2 big fat wires connected to make the test work. If the light goes out when just the small wire is disconnected, then I think that proves the diode pack is faulty.

[gilesdive]

When the ignition light is on, are other "ignition related" things on, like oil light etc?
If so it could be the key switch.
If not, I agree with the gents above.

[Pete Lewis]

if you prove its the diode pack  ring round the diodes with a meter to find which one is passing voltage the wrong way and just cut its wire, the remaining will probably cope with your charging needs,, this was a common fix by reconditioners  
ie nice paint but dodgy inards  but it will work ok till you save up for a new one   Peter

[Steve Cureton]

At one time you could buy new diode packs from any auto electrical retailer, I'm not sure you can still buy them but worth phoning around. The company I used many years ago was C.P.C Auto Electrics in Telford, 01952 249832

[thealligator]

Steve_Curton wrote:

At one time you could buy new diode packs

Yes you can still get them they are about £19 Rimmers have listed

Then you want the Slip Ring, brush set.

It is not worth it just get an exchange unit

That will have a warranty.

Fit you really want to try and repair it you may find this link useful.

http://www.mk1.connectfree.co.uk/nzalternatorrepair/alternatorrepair.htm

[andy thompson]

Alternator stopped charging this morning on the way to work... dark obviously... sat and read my book in a lay-by until sunrise and then lights off went and dropped it off at my garage for a new alternator... picked up my 2500 which is now manual.. yay

BTW Last night at 11.30 pm I popped outside and noticed the alternator was almost too hot to touch.... disconnected the battery just in case.....

conclusion... diode failure