Alternator not battery right...

[Munter]

So this is the alternator failing right? A duff battery wouldn't show this would it. (Don't want to advise someone to change the alternator against their garages advise, if it might just be the battery.)

[Munter]

stevieturbo said:

Your post seems to imply you are changing a battery because it has went flat ? Although you dont say why ?

That combined with evidence the system is far far below where it should be in order to charge a battery properly...


1+1=2

Not changing anything yet.
3 garages baffled as to why the ABS and EPS (steering) lights come on at speed and the steering gets heavy, and eventually the car stops.
1 "trusted garage")Suggested battery, can't be the alternator. Because the battery was flat when the car was recovered, but then it was able to charge it's own battery in their test drive. I suspected the alternator, and then, the owner flattened the battery completely trying to start it.
2)Speed sensor definitely at fault...
3)No idea
Honda over the phone)No idea, next slot in a months time.
Me for a while now)If it was driving then ran out of leccy, it must be the alternator....But I'm not an expert, so just checking.

[Munter]

Penelope Stopit said:

Find a good auto electrician and pay the 1 Hour labour charge for a result

The "good auto electrician" is number 2. Speed sensor or "multiplug" affecting the speed sensor reading. Nothing to do with the alternator.
Number 3 charged with changing the speed sensor says "which one? can't find anything wrong anywhere. It's not the alternator".

None of the garages want to drive the car at speed in case the steering fails again.

[Munter]

stevieturbo said:

As said.

Flat battery and evidence of battery not charging correctly....1+1=2.

And if a garage cannot figure out why a car stopped and had a completely flat battery.....seriously, stay far far far far far away from that garage.

I agree. I just thought I'd check as I'm not an expert on car electrics. And trying to tell garages to do something, they personally don't think needs doing, via a 3rd party...is proving tricky.

[Munter]

FiF said:

Agree with the good auto electrician advice. Update, OK see you have done that option.

Is it one of those systems where the charging is interfered with by a device to eke the last little bit out of the fuel consumption figures?

Imo they are a pita. On one of mine it only charges when you lift off the gas, until the battery has dropped to a certain level of charge. So if you have a long fast run at night, lights and wipers etc you can get home and despite the decent run the battery is not fully charged. A couple of days of cold weather and only short runs and you can notice a drop in cranking speed especially in a cold morning. The Ctek charger is a godsend on that vehicle.

Edited by FiF on Sunday 8th January 11:25

Even with fancy electrics, I'd have thought when the voltage starts to drop it would be designed to kick in the alternator/charging again. My suspicion is that the electrician picked up errors from a time when the systems were trying to run on 9 volts or less and starting to fail. Possibly he cleared them expecting them to return once driven. Because there's no codes my cheap £6 OBD dongle can pick up. But there's also no guarantee the dongle is any good at reading fault codes.

[Munter]

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.

[Munter]

stevieturbo said:

It is quite apparent from that graph the vehicle speed sensor is working.

The alternator needs repaired, it is blatantly obvious at times it is not charging. The only other potential issue is perhaps some wiring/connections relating to the alternator.

What vehicle is it ?

It's a 2004 EP2 Civic.

I agree with the diagnosis, but I didn't want to go storming into a garage going. "Look, it's the alternator, here's a chart to prove it, change it despite what you might think". And then find out actually if a cell dies in a battery it can have the same symptoms for x, y and z reasons that I didn't know about, and I've cost someone a lot of money they don't easily find, doing something they didn't need.

Measure twice, cut once type of thing.

[Munter]

FiF said:

Accept that the graph shows that roads peed sensor is working, wouldn't a plot versus engine revs be of use now?

Agree with earlier comment that if it's got some fancy control system should be cutting in a lot earlier.

Revs always seems to drop to -64 when at idle. Could be a feature of a cheap OBD device. I can't believe the engine would idle nicely at 800 on the dial if the ECU thought it had a negative value.

Apparently the battery was replaced between 2 and 4 years ago from the owners memory. So not original. But not fresh either.

Edited by Munter on Sunday 8th January 14:32

[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.

[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.