Alternator not charging under load

Re: Alternator not charging under load (zmit)

Thu, 10 Oct 2013 20:51:03 GMT

Alternator replaced. 14.5 volts at idle. 13.8 volts with high load. The saga continues though because my 92 only had an 80 amp alternator even though it should be a 100 amp. Seems like the engine swap from the previous owner is a pre-92 engine/alternator package.

Re: Alternator not charging under load (zmit)

Wed, 09 Oct 2013 17:20:01 GMT

Eventually got it out of the engine bay. Fins are brushing against something and it doesn't seem to be the sort of thing that can be repaired too easily..

Looks like i'm up for a new alternator now.

Re: Alternator not charging under load (bigh)

Tue, 08 Oct 2013 16:52:39 GMT

when my alt had similar issues it was the Rectifier. Most garages will be able to handle an alternator / rectifier recondition.

or if you can remove it yourself then take it to an auto elec you should save some cash. (NB it's a pain to remove tho)

Re: Alternator not charging under load (zmit)

Tue, 08 Oct 2013 12:45:19 GMT

Thanks for the reply, I need to get this car back on the road asap, so I just got one locally. I tested the bridge rectifier though and it seems that one diode isn't letting current through in either direction. Although I'm happy to replace the regulator anyway (It was probably dead as a result of the rectifier failing), I now need to sort out the bridge rectifier...
ALT fuse is fine.

Does anybody know any details about the bridge rectifier? where to find a replacement, how to fix it, part numbers, what alternatives there are, etc.?

Re: Alternator not charging under load (Road and Track)

Sun, 06 Oct 2013 21:22:56 GMT

failed regualtors are common. we can supply replacement regs or complete alternators.

have you checked the ALT fuse??

Re: Alternator not charging under load (zmit)

Sun, 06 Oct 2013 15:18:48 GMT

Yeah. That would be the 100amp.
I've tested the bridge rectifier and one of the terminals doesn't show continuity. My main reason was replacing the voltage regulator.

Re: Alternator not charging under load (track_mr2)

Sat, 05 Oct 2013 19:33:06 GMT

Mines a Gen3 Turbo not sure what the alternator is. I took the reading from the positive and negative terminals on the battery.

Re: Alternator not charging under load (zmit)

Sat, 05 Oct 2013 14:56:15 GMT

Also worth noting. The three pins on the alternator were reading 11.1v, ~11.1-11.6v (can't remember) and 12.1v at idle.

Re: Alternator not charging under load (zmit)

Sat, 05 Oct 2013 14:11:47 GMT

Yikes! That's impressive. Is that the turbo/100 amp alternator?

Checked tension. Fine. Checked/cleaned battery terminals. No difference.

The interesting part is that I pulled the engine out in 2010. It was 18 months later that this happened the first time. It's been 18 months since then as well.

Could just be coincidence. I think I have all the grounds hooked up. Trans, head, LH inspection panel.

Re: Alternator not charging under load (track_mr2)

Sat, 05 Oct 2013 12:23:33 GMT

Have you checked the tension on the alternator belt? Might be loose?
Mine charges 14.8v at idle with no load.

Re: Alternator not charging under load (Gatesys SW20)

Sat, 05 Oct 2013 12:09:28 GMT

Poor ground? perhaps

Alternator not charging under load (zmit)

Sat, 05 Oct 2013 12:05:58 GMT

Hey again,
I'm slowly taking over the 'urgent' forum.

Last night 15 minutes into a 30 minute drive home, the car started dying on me. Stereo went first, then boost gauge, then the warning lights all came on.
Voltage was down to about 10.8v
eventually jump started it and drove home.
Today I've been testing various things. I've found out that with no load the alternator charges at about 13.3v @ ~2500rpm.
With the fan on high and high beam it barely gets to 11.9v @ ~2500rpm.

The alternator was rebuilt February 2012. The battery was replaced around then too.
I had an oil leak that was caking the alternator in crud, but I've since cleaned the alternator and sorted all that out. Any ideas as to what could be causing this?