Alternator not battery right...

[paintman]

Munter said:

Penelope Stopit said:

Find a good auto electrician and get it sorted, this is an easy fix

IF you can find one. Yes I thought that. But at £60 a go... Cash rapidly get's tight testing the local auto electricians worthiness.

You'd think the chap top of the yell recommendations and in business for over 10 years would be a good idea...but...speed sensor.

Paid for it. https://business.yell.com/yell-com/

[Munter]

paintman said:

where the warning light would come on

I should say the "battery" light never even seems to flicker. Only comes on apparently when the whole thing dies a death, and I've seen it before the engine is started so the bulb does work.

Would that add weight to the smart charge theory? E.g. if the car doesn't think it needs to charge, it wouldn't worry about putting the warning light on despite OBD reading 9 volts.

[PositronicRay]

I may be may off the mark here. But would a 2004 Honda have a smart charge system? I came across something similar where the alternator brushes were knackered, lifting off @ speed therefore not providing a charge except @ tickover. It was a much older model though.

[Munter]

PositronicRay said:

I may be may off the mark here. But would a 2004 Honda have a smart charge system? I came across something similar where the alternator brushes were knackered, lifting off @ speed therefore not providing a charge except @ tickover. It was a much older model though.

Reading online it sounds like they have had dual mode charging in Hondas since the late 90s. The description of which would fit the start of my graph where the volts bounce around between 12 and 14, until on the motorway the whole thing seems to go to pot. Any time it's below 50mph/2500rpm(ish) it seems to be in the range expected from dual mode charging.

I think the balance of opinion is it's more likely to be the alternator than anything else. But it could be the smart/dual charging circuit, and/or a poor battery confusing the charging circuit/ecu logic. Without methodically checking/testing each of those it's not possible to diagnose any further.

She's going to take these ideas, and the charts to the garage that seemed the most competent. If the concept of dual mode charging produces a blank look, try somewhere else.

[Penelope Stopit]

paintman said:

Munter said:

Penelope Stopit said:

Find a good auto electrician and get it sorted, this is an easy fix

IF you can find one. Yes I thought that. But at £60 a go... Cash rapidly get's tight testing the local auto electricians worthiness.

You'd think the chap top of the yell recommendations and in business for over 10 years would be a good idea...but...speed sensor.

Paid for it. https://business.yell.com/yell-com/

Read. I also posted this

You and many others may think that the chap at the top of yell is the man but it doesn't work that way and i understand your frustration, i took a quick glimpse at your profile and gather you are in the Midlands, there are bound to be plenty of gooduns where you are but the problem is finding one of them, if I was you I would phone a few new car dealers and explain your problem before asking them who they use when there workshop staff can't fix one of their new sold cars that has a difficult to find electrical fault, this is a fool-proof way of getting hold of a goodun

[FiF]

OK further thought, in terms of the output voltage, what effect does increasing load have, eg switching headlights on, heater fan, heated rear window and so on?