Hi Guys
As title just fitted a new alternator wired the warning light to L and the switched feed to IG as per the old unit. Warning light stays on all the time and gets brighter as i rev the engine. The alternator is working as it is giving the battery over 14volts? messed about with it no I cannot get the warning light to come on at all????? any ideas as to what is wrong and what i might have done?

If you are sure it's wired up OK then light that stays on and gets brighter at high revs usually means duff voltage regulator. If you have since been plugging and unplugging while its running or running with any wires disconnected you could have killed it.

Use a meter to see if the current reverses once the engine is running, if so diode indicated in line with the bulb.

Its not unusual to have to do this on some alternators BTW.

[Edited on 21/9/10 by mark chandler]

HI Mark
I understand about testing the output but what do you mean by.

"if so diode indicated in line with the bulb" can you please explain this

thanks Simon

The voltage reverses, the bulb gets driven the wrong way.

Connect the mulltimeter and the needle will deflect one way, start the car if it jumps the other way then thats your problem.

From memory connect the diode with the band pointing towards the alternator, get one from maplins, cost pennies something like this Link thing

Have you got a 12V feed on the dash side of the warning light? This light usually only switches on when one 12V feed (dash or alternator) is earthed. From your description it would appear that your alternator is working ok and connected to the warning light ...... so I would check the other side of the warning light


[Edited on 22-9-10 by RazMan]

thanks for all the help guys, tried it again and the alternator is charging the battery at nearly 15volts. This is way to high as it should be 13.8 for a 12volt battery. I will be getting a new one today so will give this a go tonight.

PS checked all the wiring and do have a switched 12v on the other side of the bulb. It all did work i just think I have a duff alternator? will see later

15V is not all that high if your battery is low on charge but 14.5V is considered normal. Have you just fitted a new alternator and consequently had problems with the warning light? If so you might just have the wrong regulator fitted - this happened to me and I swapped out the regulator for an alternative one..... problem solved.

[Edited on 22-9-10 by RazMan]

If I had hair i would pull it out

Got the new alternator (same as the last one) put it on and guess what no charge? tried it with just the battery lead connected and it was not outputting any voltage? put the warning light and switched feed to the rear plug and the light stays on and gets brighter when the engine revs.!! back to the start.

Not sure what i am missing but here are my settings

switched 12v to 1 side of the warning light
output from alternator to warning light from L terminal
switched feed to alternator IG terminal
Battery wire from alternator to starter then onto battery

any more ideas to try would be great!!!

PS this has worked for the last seven years????

Can you compare the regulator part numbers? If you whip the cover off it will pop out after removing a few screws. Quite often they can be quite different circuit wise but look identical.

What is the battey voltage with the engine not running?

Have you got access to an inductive ammeter?

Chris

HI
The battery is fully charged at just over 12v. Its a new one.
I have ended up taking both alternators back and have found someone who can recon my old unit. I think this is the only way to confirm that i do have a good alternator and that it will work on my car*hopefully).

Thanks again for all the replys as always great help and information.