Intermittent battery charging problem.

[BALDYMONSTER]

So when driving to ASDA earlier the battery warning light came on and my disbursal voltmeter showed the battery was down on power.

When I stopped I had a look at what I could and obviously checked the battery connections which all looked and seemed fine.

On driving home the issue continued and then the brake fluid level light came on as did the alternator light, here:





Car seemed to idle a bit higher than usual as well, say 1200 rpm, but a hard burst of acceleration and the lights went off and the battery started charging again. Then a mile later the same thing happened and put my foot down and it was all fine again. Alternator is about 18 months old and had to get some sort of adapter connection when it got the rev 3 rear clip installed.

Seems like just a loose connection or similar, anyone else had this happen or somebody electrically minded point me in the correct direction.

Thanks.

[benckj]

Giving your symptoms I’d guess the alternator rectifier is failing. Often it will result in intermittent voltage levels as the regulator has broken or shorted diodes. What did you actually replace 18 months ago (new, rebuilt or re-conditioned)?

[jimi]

A fairly common fault on MK2's is broken cores in the wiring to the alternator, this article explains how to diagnose whether it's a wiring or alternator problem https://www.mr2oc.co.uk/component/fss/? ... kbartid=51

[benckj]

Interesting article on testing alternator. Never suspected a wiring fault issue is common on MR2’s. Must occur at a flex point somewhere like the door harness.

[jimi]

They often go somewhere in the harness that runs along the inlet side of the head, I've repaired two that have gone there and one that had a broken wire down close to the alternator plug. whether it's down to heat and vibration (or flexing) I don't know, so I'd say it's not an everyday fault but common enough to be checking before changing the alternator, mainly a MK2 problem, but not unheard of on the MK1 as well. Not aware of anything similar on the MK3, but that may come with age.

[SonicSW20]

That wiring fault seems to be much more common on earlier SW20's, we'll see if it crops up on more Rev3/4/5's over the next few years to test that theory I guess.

[jimi]

That wiring fault seems to be much more common on earlier SW20's, we'll see if it crops up on more Rev3/4/5's over the next few years to test that theory I guess.

Can't remember the years of the cars I worked on seem to remember a couple of N/A's and a Turbo. age/mileage may well be a factor, as you say time may well provide some clarification

[MR2DI4]

The four red dash lights of death.

Currently having the same problem. The diodes in the rectifier pack of the alternator were fried in mine. 3 of the 6 diodes were dead causing intermittent charge and very little charge at idle.

Its new alternator time.

[BALDYMONSTER]

The alternator was new 18 months ago, brand new not a cheap recon.

It’s gone pop so it’s in getting done this week.

[MR2DI4]

The alternator was new 18 months ago, brand new not a cheap recon.

It’s gone pop so it’s in getting done this week.

Define "New" . I just bought a "New" Alternator and its largely crap. I would give it a life of 2 or 3 years if used as a daily driver.

The problem is that they are not always 100% new on the inside.

I came across a post while searching that said either MR Ben or RareElectrical were the best for MR2 Alternators.

You can cross Eagle Automotive off the list, it doesn't fly.

For a major forum only about MR2's there should be much more information about Alternators, whats good, whats bad, part numbers and suppliers for parts for them. I have been days on Google so far and I'm chasing my tail in this part of the world. Cannot get actual dimensions from people selling the Diode Rectifiers on E-Bay to check fitment so I'm off to a local supplier on Wednesday with my faulty ones to check for a match.

[BALDYMONSTER]

New alternator fitted last weekend.

Problem solved.