What's new

Strange battery/charging fault

StuH

Members
Messages
374
Reaction score
53
Location
Lancashire
Car
Superb Estate 3.6 V6
I've posted this on the other forum but hoping for some more input/thoughts:

When braking I get a very fleeting message on the dash, at first i couldn't catch the message. However, its started staying on longer, the message is 'Check System' with a battery icon next to it, the red charging light doesn't isn't coming on. I've felt I've had a battery issue for a few weeks so changed it three days a go, the alternator is about 6 months/1500 miles old (though a reman). Serpentine belt was changes at the same time as the alternator.

Using a DMM I'm measuring 14.2v when running, grounds I can see look okay and there's no codes. My previous Accord had a failed brake switch but that threw up a code. An obvious cause I suppose would be a brake bulb fault or bad fitting but I can't see anything (need to do some more digging), could be another alternator issue or voltage regulator. Not sure??
 
Try braking with your foot down on the clutch (or in neutral gear) and see if that makes any difference
 
ahhh hmmm ok, the idea is to separate a fault in the alternator charging from a fault in another aspect of the charging.

yeah try it in neutral, but I take no responsibility if you crash of course ;)

Engine will be idling, keep an eye on the rpm, if the light comes on and rpm drops then something might be causing the alternator to partially seize (internally). If rpm does not drop and the light comes on, then it might be a loose connection somewhere ?
 
Well tried to get something to work with this morning and nothing, diddly squat, not a message to be seen. I'm going to change the bulbs just for peace of mind, as much as that's unlikely to be the problem.
 
Can't you simply test the bulbs by having an ***istant push the brake pedal while you inspect the rear to see if one side is brighter than the other, or if the high level LED display is all working properly? That high-level unit could cost a fair bit to replace!
 
Jon_G said:
Can't you simply test the bulbs by having an ***istant push the brake pedal while you inspect the rear to see if one side is brighter than the other, or if the high level LED display is all working properly? That high-level unit could cost a fair bit to replace!
Yes I've done that, but the fault is when driving not stationary specifically when braking or I think occasionally when going over a bump. Couldn't replicate it this morning.
 
Jon_G said:
Intermittent problems are the worst!
Tell me about it! My old battery was knackered and causing a few other problems which have been sorted with a new battery.
 
Jon_G said:
Intermittent problems are the worst!
Agreed the hardest to diagnose and fix
 
Definitely getting a drop when braking from 40 upwards, drops to about 12.7v then recovers when accelerating, also think there's a rumble that rises and falls with revs. Clearly first thought is alternator but I put a reman on just under a year ago and it's not done many miles.
 
Seems like it starts to happen when the engine has warmed up. Got to say the alternator was really hot after a short run, not sure how how alternators run?
 
Across the battery terminals but today I used a meter that plugs in the *** lighter. When I got the message on the dash I had a look at the meter in the socket and sure enough it had dropped.
 
StuH said:
Seems like it starts to happen when the engine has warmed up. Got to say the alternator was really hot after a short run, not sure how how alternators run?
An alternator is a 3-phase AC generator with diode rectifiers to give a DC output.
This one has the voltage regulator built into the alternator casing, which receives feed signals from the ECM (which takes a signal from a current sensor).

But the rumbling is probably coming from the bearing on the shaft, see if the pulley moves around a bit, it might be loose and getting slightly seized during braking.
 
I've never noticed an alternator getting particularly warm and the voltage shouldn't be dropping as low as 12.7v with the engine running... I strongly suspect the recon'd alternator has become faulty, Strange that braking shows up the fault though, rather than something that takes more current (such as the headlights).

Measure the battery voltage with the car idling and turn on all the headlights, the HRW, foglights and blower. If you rev the engine to 1500 rpm or more the alternator should be able to keep the voltage at 14.2v or higher (and the alternator shouldn't become noisy).
 
I've tried it with everything on and the lowest I can get it is 13.9v but it's only when it's been running that the problem occurs. I suspect when the brakes are applied for a certain speed or above the load is removed from the alternator and it temporarily throws the fault. Anyway, spoke to the supplier of the part and he's just been and dropped off a replacement. That's good service.
 
Changed the alternator this morning, went much quicker this time! Not had the message yet but only done a small trip. The pulley on the old one feels quite stiff and squeals when rotated. Don't know if this was the problem.
 
StuH said:
Changed the alternator this morning, went much quicker this time! Not had the message yet but only done a small trip. The pulley on the old one feels quite stiff and squeals when rotated. Don't know if this was the problem.
The stiffness and noise will merely be symptoms of the problem. The electrical shortcomings suggest that the alternator windings may have become loose and are somehow fouling the rotating ***embly?
 
Sounds like duff bearings in the alternator, during a journey they'll get hotter and hotter, and take more energy from the engine. During braking the engine goes into injector cut off, hence the alternator voltage reduces.
 
After a 10 min run it was incredibly hot, I'm sure it shouldn't be that hot.
 
What is the battery voltage when disconnected at one terminal ?

Try first thing in the morning, after the car has been standing overnight.
 
Let us know how you where did you get both alternator from ?

Sent from my C6603 using Tapatalk
 
fair enough looks like decent company, keeps us posted in a week or so, hopefully with a good update :)
 
Channel Hopper said:
What is the battery voltage when disconnected at one terminal ?

Try first thing in the morning, after the car has been standing overnight.
Sorry, not sure I follow. Do you mean measure from the alternator with one of the battery terminals removed?
 
The problem returned. Changed the auto-tensioner, no joy. Cleaned the PCV valve and noticed the throttle body had a build-up around the butterfly valve so that got cleaned. Cleaned as many electrical connectors as I could easily get to. I've not had the fault yet, but it's too early to say, car drives much better though!

Still got this strange issue with the tailgate; a short journey and it will work fine from the key fob. Anything more than 10 mins and the boot wont work off the fob but will work using the button on the dash and always closes using the button on the tailgate. Leave the car standing for 10 or so mins and it'll work again! bizarre. Though it was related to the alternator issue but not so sure...
 
Im suspecting some broken wires causing intermittent connections have you checked wiring loom also did you clean exterior handle

Sent from my C6603 using Tapatalk
 
Top