Alternator issues

Technical questions and answers about the Mazda Bongo

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sotal
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Alternator issues

Post by sotal » Thu May 19, 2022 6:22 pm

I've just put a new battery in.

Measured the voltage at 12.59V before putting the battery in.

Connected up and started the bongo up. Instant start up.

Measured the battery at 12.1V with the engine running.

Gave it about ten minutes and the battery was at 12.14V.

Turned the engine off and the voltage went to 12.4V

Pulled the passenger seat up the alternator belts are ok and the tension seems ok, the alternator body is very hot though. I could hold my finger on for about 5 seconds before it became uncomfortable.

The Aircon unit below is cold to the touch. The Aircon belt is far too slack so that needs sorting but shouldn't be related.

Any ideas for the alternator?

Strangely the warning light doesn't light up in the bongo, it is there in the self test but when I've had alternator issues in the past in other vehicles the battery light normally shows but I've got no warnings etc.

It hasn't been used much over the last few months.
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Re: Alternator issues

Post by g8dhe » Thu May 19, 2022 6:41 pm

Not totally certain which type of detection circuit is used on the Bongo alternators. Some are merely rotation detectors, others are based on charging voltage more modern ones are a lot more clever!

Suggest you check the voltage at the alternator itself rather than at the battery, as it might be a problem between alternator and battery, also make sure that the field winding is being powered on the diesel its via the headlight fuse.
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Re: Alternator issues

Post by sotal » Thu May 19, 2022 7:07 pm

The voltage at the alternator matches the battery voltage.

So too low there too.

The headlights work so the headlight fuse is intact.

How do I test the field winding contact? Is it part of the multi plug that goes into the alternator?
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Re: Alternator issues

Post by sotal » Thu May 19, 2022 7:29 pm

I disconnected the plug that has two wires going into into.

I tested these wires with the engine running and the connector disconnected (black to the alternator body, red to the wires). The brown chunky write had 12.1V

The thinner wire had 11.4V.

Plugging the plug back into the alternator causes the revs to dip a little, unplugging it again causes them to rise.
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Re: Alternator issues

Post by g8dhe » Thu May 19, 2022 7:38 pm

It sounds like the regulator inside has failed, you might find its a lot cheaper & quicker to have it refurbished by a local firm than to buy a new one.
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Re: Alternator issues

Post by sotal » Thu May 19, 2022 7:49 pm

Thanks, I've found a place 10 minutes from my work. I'll give them a call and see if it is something they can do.
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Re: Alternator issues

Post by sotal » Thu May 19, 2022 9:12 pm

Removed alternator and the three belts. The belts are ready for the bin. So a new set of belts required as well.

Will see if the electrical place thinks the alternator is repairable.
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Re: Alternator issues

Post by sotal » Sun May 22, 2022 9:06 am

Couldn't get hold of the electrical bloke, so took it apart for a look.

Removed the rear cover, desoldered the windings and removed the regulator/diodes.

One of the diodes was visibly melted and bits of melted plastic were dropping out during the dismantling process.

From hunting online it seems like I can get a replacement diode pack but only in 80A or 70A, not in the 90A. It looks like the refurbished ones mostly used these too as they are mostly rated at 80A.
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Re: Alternator issues

Post by g8dhe » Sun May 22, 2022 10:25 am

If you search the posts on here around 2010 time you will find quite a few failures of alternators after around 12 months when lower rated diode packs were used.
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Re: Alternator issues

Post by sotal » Sun May 22, 2022 11:28 am

g8dhe wrote: Sun May 22, 2022 10:25 am If you search the posts on here around 2010 time you will find quite a few failures of alternators after around 12 months when lower rated diode packs were used.
Yes I don't fancy fitting a lower capacity diode pack, but most of the refurb ones seem to be 80A too. So currently searching for a reasonably priced refurb unit that actually had the 90A pack.
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Re: Alternator issues

Post by teenmal » Sun May 22, 2022 8:11 pm

sotal wrote: Sun May 22, 2022 11:28 am
g8dhe wrote: Sun May 22, 2022 10:25 am If you search the posts on here around 2010 time you will find quite a few failures of alternators after around 12 months when lower rated diode packs were used.
Yes I don't fancy fitting a lower capacity diode pack, but most of the refurb ones seem to be 80A too. So currently searching for a reasonably priced refurb unit that actually had the 90A pack.


Eurocarparts
or
https://www.startermotor-alternator-sto ... 2681-p.asp
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Re: Alternator issues

Post by Alkers » Mon May 23, 2022 3:29 pm

Just to add that I've replaced my bongo alternator twice (using second hand parts). The first time I had the flashing glow plug light on the dash as you would expect but the second time there were no symtoms other than the battery not being charged.
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Re: Alternator issues

Post by sotal » Mon May 23, 2022 7:00 pm

Alkers wrote: Mon May 23, 2022 3:29 pm Just to add that I've replaced my bongo alternator twice (using second hand parts). The first time I had the flashing glow plug light on the dash as you would expect but the second time there were no symtoms other than the battery not being charged.
Yes mine was exactly that, no warnings etc, just no charging.

I spoke to the electrical place today, be recommended trying to find a second hand one! He quoted £55 to replace the diode pack plus it might need a regulator too, which makes it more like £100.

Might as well replace at that sort of price.
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Re: Alternator issues

Post by sotal » Mon May 23, 2022 7:02 pm

teenmal wrote: Sun May 22, 2022 8:11 pm
sotal wrote: Sun May 22, 2022 11:28 am
g8dhe wrote: Sun May 22, 2022 10:25 am If you search the posts on here around 2010 time you will find quite a few failures of alternators after around 12 months when lower rated diode packs were used.
Yes I don't fancy fitting a lower capacity diode pack, but most of the refurb ones seem to be 80A too. So currently searching for a reasonably priced refurb unit that actually had the 90A pack.


Eurocarparts
or
https://www.startermotor-alternator-sto ... 2681-p.asp
£273 (including the 45% off discount!) At ECP

The other one looks good but is out of stock
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Re: Alternator issues

Post by sotal » Mon May 23, 2022 7:11 pm

https://vi.raptor.ebaydesc.com/ws/eBayI ... spheader=1


What are your thoughts on the above? £90 delivered

The part number matches and it says it is 90A and it has a 2 year warranty.

But it doesn't list the bongo as a compatible vehicle.
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