alternator not working after welding work

[nesty]

Hi

I have had my T25 welded for the MOT.

I collected the campervan anyway got 1/2 mile down the road and noticed the alternator light on. (TBH probably been on since I collected it) but didn't notice at first.
I have battery voltage indicators and there is no current going to the battery.

Can welding (if the battery wasn't disconnected) during the work screw an alternator up?

[shepster]

I have heard you're meant to disconnect alternator when welding, never bothered myself though, have the garage pulled the plug off but forgot to re-connect?

[ZsZ]

Yup, the diodes inside do not like the high current that the welding cause.

[nesty]

Thanks for the replies. There is no plug on my alternator just the usual connection nuts.

How much is a diode repair?

I am not sure if I'll be able to raise this with the garage?

[California Dreamin]

Thanks for the replies. There is no plug on my alternator just the usual connection nuts.

How much is a diode repair?

I am not sure if I'll be able to raise this with the garage?

Because? as 'professionals' they will be aware of the risks when welding....risks that include damaging vital electronics. They will also be aware of the preventative work needed before carrying out this task...they obviously chose to cut corners by leaving things connected.
I guess they believed that in most cases no damage would occur.

Martin

[sarran1955]

Hello,

Hope you havn't got a fancy radio or alarm.....

Cordialement..

[kevtherev]

How much is a diode repair?

Not much, a local alternator repairer should do it easily.

[Jakemate]

Just disconnect the battery negative when welding, every garage should know that! Yes go to a local auto electrical firm or alternator re conditioners to replace diode pack.

[ZsZ]

Just disconnect the battery negative when welding, every garage should know that! Yes go to a local auto electrical firm or alternator re conditioners to replace diode pack.

The best is to disconnect the alternator also.

[CovKid]

I've never come across this at all - ever. Electricity likes the shortest route. Its possible certainly but could also be coincidence too. A lot of welders do disconnect it though so clearly the diodes are a weak point.

Found this though: http://www.ukwelder.com/forum/lofiversi ... t6629.html" onclick="window.open(this.href);return false;

[ghost123uk]

This happened to my mate Stuart (with a Bay window van) and it did "take out" his stereo as well. The bodyshop rang him to admit their error and replaced both alternator and radio. In fact he got a much better radio out of it !!

[bigherb]

Yes it is well know in the trade. The high welding voltages can overcome the maximum reverse voltage of the rectifier diodes and any other electronics blowing them. Disconnecting the battery only will not help it only stops the battery getting damaged all electronic components need to be disconnected so there is no voltage path through them.

[nesty]

The alternator is all ok I had it bench tested.

There is a fault somewhere in the wiring. The bloke said the light being on is preventing the alternator being energised.

Probably a fault in the blue wire somewhere. I am sure this subject been discussed on here. Can anyone give me a link to how to check the alternator wiring.

Thanks

[bigherb]

Easy to check.
Switch the ignition on don't start the engine, light should be on, disconnect the blue wire from the alternator (or if it has the three wire plug pull the plug out) the light should go off. If it stays on then a wiring fault, if it goes off then a faulty alternator.

[nesty]

Hi All

The problem is solved. I just read up about the alternator not exciting. I wondered if it was that.

I revved it hard for 15 seconds then the light went out and power all restored. What the issue was I don't know.

All good now. Thanks for the advice all!