Weird electrical problem - C4 GP mk1

[MixerFistit]

Newer car, newer problems.
I've binned the xsara picasso for a 62 plate mk1 C4GP, unfortunately I have an odd electrical issue.

On a long journey I did get a "battery charge or electrical supply faulty" message but that then disappeared - this was still daylight. I was able to complete the rest of the long journey with lights on and then no issues restarting the car in the morning (-2 C).

The only symptom I'm seeing now is that when the E-handbrake is on my voltage is around 14V (off a scan tool) and drops to 11.1V when the handbrake is disengaged. If the blower is set to maximum there is a very noticeable change in speed that matches the change in voltage.

So the main questions are, has anyone seen this before? And presumably it's an grounding issue, so does anyone have a good starting point for me to begin investigating?

(It's a recent purchase from a business but if I can resolve it myself it would be more convenient for both parties. They're happy to pay for the fixes but then I have to get the car in for repair.)

VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Can't help you without any specific fault codes - if you have any, pop them up.

Obviously the Fan takes a lot of power and will cause a drop in voltage. The EPB just operates the rear brake cables to apply and release the braking cables to the calipers.

I would be checking you battery to be honest. How old is the battery? If older than 5 years, time for a change as starting may not be an issue, but the reduced capacity of the battery overall is a hidden issue you won't see without proper battery testing kit and time to test the battery overnight.

[MixerFistit]

Hi Marc,

I'll be putting a new(ish) silver Varta battery on later from my old picasso, if it fits. Just to clarify, the voltage drop is persistent for as long as the handbrake is engaged, stays at 11V even while the engine is running, and jumps back up as soon as the brake is released. It's like as of the brake is somehow disengaging the alternator.
No fault codes from the scanner but lexia will be on it tonight so I'll hopefully have more info

[MixerFistit]

OK, so the newer battery has been installed and although the voltage drop isn't as extreme its still there (eventually dropping from 13.5V down to 12.4V). This is a very good powerful battery so it's pretty resilient.

Will be looking at lexia later on but not sure what to look for - hopefully there'll be a code

[GiveMeABreak]

It may only be temporary as the EPB is controlled by the ESP ECU, which is controlling the handbrake ECU and the motors in readiness for application / release. As soon as the EPB is applied and the engine switched off, of course it is no longer an issue, as it isn't when released. So nothing to worry about there as far as I can see.

[MixerFistit]

Can't help you without any specific fault codes - if you have any, pop them up.

Obviously the Fan takes a lot of power and will cause a drop in voltage. The EPB just operates the rear brake cables to apply and release the braking cables to the calipers.

I would be checking you battery to be honest. How old is the battery? If older than 5 years, time for a change as starting may not be an issue, but the reduced capacity of the battery overall is a hidden issue you won't see without proper battery testing kit and time to test the battery overnight.

OK connected with Diagbox and saw a LOT of faults but quickly realised the majority were probably linked to my recent P0087 incident (stuttering, STOP message etc when going over 3k rpm) which seems to have been resolved after replacing the filter, I didn't clear that fault at the time with my basic scan tool incase it wiped something important with the electrical issue.

After clearing all the injection/ignition faults I'm left with 2 BSI faults that persisted (even after a quick blast up the bypass for a few miles the fuel related faults have not returned):
A4C9 RH rear Fog lamp short circuit to positive (I've confirmed the RH lamp is indeed not functioning)
C994 Fusebox: fault in the aircon compressor clutch control circuit (confirmed the aircon does not function but I had assumed it was lost gas due to age)

I haven't gone any further with these 2 faults, I'd be surprised if the fog lamp is an issue but will remove it to make sure, they're relatively low down on the back and maybe prone to water ingress? Not sure where to start on the aircon circuit and may not be relavent anyway.

Despite changing the battery as mentioned earlier, I continued to observe erratic voltages. Driving above 30 seems to get the voltage back to 13V, engine braking down a small hill seems to increase voltage up to nearly 14V, parking with handbrake is still repeatably increasing voltage complete with increased fan speed.
Tonight, I parked up after the bypass run and left the handbrake off with my foot on the brake and engine idling, after about 10minutes the battery charge error message came on and the voltage was at 11.2V but as soon as the message came up the fan seemed to increase in speed slightly almost immediately (voltage jumped to 12.5V). I did nothing for 2 mins and finally activated the handbrake. The voltage jumped to 13.5 and within a minute the battery light went off and error message cleared.

Bonkers

[MixerFistit]

Swapped the bulbs around and the fault stayed with the RH rear fog lamp. I'd like to pull the fuse that protects this circuit in case it's causing my main issue and have looked at the wonderful user manual and can see no mention of fuses for the rear fog lamps. Saw somewhere in this or another forum about trying either F12 or F33 in the glove box but neither of them had an effect on the good lamp.

Does anyone know which fuse would likely control the rear fog lamps (or any of the rear lamps for that matter)

[Hagrid]

I tried looking through the 2 or 3 manuals I have downloaded; curiously none of them identify fuses for any of the exterior lights (except the headlights, whose fuses are under the bonnet)! The following table is copied from a May 2008 C4P/C4GP manual:

Fuses under the dashboard
Fuse N° Rating Functions
F1 15 A Rear screen wipe
F2 30 A Locking and unlocking earth
F3 5 A Airbags and pretensioners
F4 10 A Multimedia, photochromic rear view mirror, particle filter, diagnostic socket, air conditioning, manual headlamp height adjustment
F5 30 A Front windows, front door electronics control pad, panoramic glass roof
F6 30 A Rear windows
F7 5 A Interior lamps, refrigerated glovebox, radio
F8 20 A Multifunction screen, radio, steering wheel controls, multimedia, deflation detection, alarm, trailer
F9 30 A Multimedia, front 12 V sockets, torch, radio
F10 15 A Height corrector (suspension)
F11 15 A Brake switch, ignition switch
F12 15 A Parking assistance, automatic screen wipe and lighting, passenger’s electric seat, lane departure warning system, Hi-Fi amplifier, trailer
F13 5 A Engine relay unit (BSM), driver’s electric seat
F14 15 A Air conditioning, Bluetooth® hands-free kit, automatic gearbox lever, airbags, instrument panel
F15 30 A Locking and unlocking
F16 - SHUNT
F17 40 A Heated rear screen
F29 20 A Heated seats
F30 - Not used
F31 40 A Trailer relay unit
F32 15 A Rear 12 V socket
F33 5 A Parking assistance, automatic screen wipe and lighting, passenger’s electric seat, lane departure warning system, Hi-Fi amplifier
F34 5 A Trailer
F35 - Not used
F36 20 A Hi-Fi amplifier
F37 10 A Air conditioning, light pack
F38 30 A Driver’s electric seat
F39 5 A Fuel flap
F40 30 A Passenger’s electric seat, panoramic glass roof

Fuses in the engine compartment
Fuse N° Rating Functions
F1 20 A Engine management
F2 15 A Horn
F3 10 A Screen wash pump
F4 20 A Headlamp wash pump
F5 15 A Engine components
F6 10 A Xenon dual-function directional headlamps, automatic headlamp height adjustment, clutch switch, protection switch box (BCP)
F7 10 A Automatic gearbox, engine coolant level switch, power steering
F8 25 A Starter motor
F9 10 A Stoplamp switch
F10 30 A Engine components
F11 40 A Rear blower
F12 30 A Screen wipe
F13 40 A Built-in Systems Interface (BSI)
F14 30 A Air pump, heat exchange saver
F15 10 A Right-hand main beam
F16 10 A Left-hand main beam
F17 15 A Left-hand dipped beam
F18 15 A Right-hand dipped beam
F19 15 A Engine components
F20 10 A Engine components
F21 5 A Cooling fan relay

Fuses on the battery
Fuse N° Rating Functions
F1 5 A Automatic gearbox actuator
F2 5 A Stop switch
F3 5 A Battery charge estimation ECU
F4 20 A ESP supply
F5 5 A ESP supply
F6 20 A ECU for 6-speed electronic gearbox/automatic gearbox

[MixerFistit]

Thank you Hagrid, a noble effort but unfortunately my manual, despite not showing anything useful, does at least match my fuse boxes.

Now some good news - hopefully!

I do seem to have resolved the original issue. Either by resetting the BSI again or by removing the driver's window controller

Basically, I tried running a temporary earth from battery to a good ground point and there was no difference. So after reconnecting the battery I went to sort the antipinch on the windows. My rear left window wouldn't come back up but when pulling on the switch the interior lights would dim a little indicating it was trying. Thought I'd try a BSI reset again just in case it was getting muddled - still no window.
Then realised my window control was the same crap as I had on my C8 so probably needed a clean. A bit of wiggling and realised it was mixing up the up/down.
Removed the connectors and then thought to test my original issue.
The fault has now gone (for the time being at least). I suspect this final BSI reset has cured the issue and the window issue was coincidence.
I've noticed my side/headlights now function without the ignition on - they wouldn't work prior to this, I didn't think anything of it at the time, just assumed it was a quirk of this model, so it really does look like a software glitch all along.
I still don't have a rear RH Fog lamp though but that's not as bad as where I was...

[MixerFistit]

Unfortunately fault has come back this morning.
Driving with lights on battery 11.1V, engine braking voltage up to 13.8V, put the clutch in and voltage drops steadily to 11.1, clutch out voltage back to 13.8, touch the accelerator and voltage drops again.
Handbrake on idle still has same effect as before. And lights don't come on unless the key is turned. Probably time to give way to some expertise unless anyone has any suggestions

[Hagrid]

The dimming interior light suggests a heavy electrical load; given what was going on I'd suspect the winder motor was trying to turn but jammed. So maybe the regulator etc behind the door card needs a checkover?

Not sure what you mean by mixing up the up/down - was the window going up when you pressed down and vice versa? Or was the window motor being given up and down commands at the same time? How is it able to reverse direction - does it have two opposing coils and were both being energised at once? That could lead to the motor 'freezing' and the dim lights.

Try blocking a good window from closing with your hand and see if that also dims the lights before the cut-out kicks in.

On the other hand, you might possibly be right about the door window switches; the controls in the n/s/r door of mine don't work and I have to open it using the controls in the driver's door (no, this isn't down to the child lock), and this must have been a pig of a problem for the dealer who sold me the car because he left a spare (or the old) driver's door switch panel in its door pocket. I mention this merely because it could point to a common problem with C4 door window switches.

Although I now have a 2008 C4GP I've had it less than a year and hardly touched it, so my specific knowledge is nothing like what I picked up as an owner of two M59 Berlingos over the last decade. Using that knowledge, I almost daren't mention it because it always gets blamed, but I wonder whether your sidelights and foglights issues are both down to the com2000, the stalk unit behind the steering wheel? There are tons of YT vids showing how to do things to their stalks, which if nothing else does suggest that this is a component liable to fail because it gets used so much. Yes, the biggest complaint is loose or wobbly stalks, which I don't think applies here, but there is a lot of complicated switchery inside them and it is one place where shorts and PCB track failures could occur.

A last thought, thinking again of your EPB and other electrical oddities - I wonder if there is a permanent drain on the batt somewhere, not enough to be a problem in its own right, but when other power-hungry devices are turned on (i.e. electric motors, solenoids, etc) then the combined drain is too much for the batt and causes all those gremlins? Or the drain leaves too little available power in the batt to operate the window motors and EPB correctly, causing their issues as they try to work with too little power?

If there is such a drain, I would guess it only drains power when the ignition is on or the engine running, otherwise the batt would go flat when the car is parked up of course.

[MixerFistit]

The lights dimming was the window trying to go down when it was already down. My drivers side controller is a bit faulty so prone to issuing the wrong command (down instead of up) - pretty common I think as I had the same issue in my C8 and it looked very similar but either way, it wasn't relevant to my main issue, it seems the BSI reset was what temporarily fixed the issue. I'm beginning to suspect a software issue as after a 30 mile run today, my battery light came on accompanied with the "battery charge/electrical system fault" error and I had the live voltage monitoring on at the time, bizarrely the instant the error came up, the voltage jumped back up to 13.5+ this persisted until the battery light went off a few minutes later and then the drain came back.
So another question is: does the BSI turn anything off when the charge fault message comes up and if so, what?
Or could it just be a software glitch (I've heard some alternators are software controlled) and is that glitch just a glitch or is it caused by another fault. If it's dry tomorrow I'm going to try to tackle the rear RH Fog lamp, to see if I can at least clear that fault. May get lucky and fix the whole issue!
Oh and as for the potential drain with the EPB, don't forget, the same behaviour is observed when idling/accelerating (drain) vs engine braking (charging) so it's not just the EPB that can control the fault. I wonder if activating the EPB adjusts anything else to do with the engine the same way as engine braking would (close a flap here, switch off a sensor there)?
In the meantime, help and advice still very much welcome.

[GiveMeABreak]

Your best bet is still to have it properly diagnosed with Lexia / Diagbox and provide any fault codes as the systems are so interconnected you could be running round in circles otherwise.

[Sloppysod]

.......... don't forget, the same behaviour is observed when idling/accelerating (drain) vs engine braking (charging)..........

I always look for the easy to spot/fix items first so, when you accelerate the engine will try to rotate around the drive shafts on the engine mounts, and on deceleration it tries to rotate the other way. Could it be as simple as the electrical connector/connection on the back of the alternator or an earth ?

[MixerFistit]

Your best bet is still to have it properly diagnosed with Lexia / Diagbox and provide any fault codes as the systems are so interconnected you could be running round in circles otherwise.

Hi Marc, you may have missed it due to my long ramblings of my investigations but the only lexia faults I get are the same 2 as before (both electrical though suspiciously):

A4C9 RH rear Fog lamp short circuit to positive (I've confirmed the RH lamp is indeed not functioning and I still haven't found a way to isolate - I'm a bit wary of fuse pulling at random)

C994 Fusebox: fault in the aircon compressor clutch control circuit (I can only confirm the aircon does not function/clutch doesn't engage but a/c button lights up)

Neither of these faults would clear.

@ Sloppysod, I did temporarily run 2 sections of 3 core flex 13A copper (all 6 cores twisted together) from the Neg to an earth point just to see if the symptoms would disappear but there was no change. Also a twisting motion from the engine doesn't fit with the EPB observation.

I suppose logically it must be a high drain device causing the issue because I have a beefy Varta that wouldn't normally dip too much under a decent load but even without the blower on, the drain still happens albeit a little slower but at the same time it's like the alternator stops charging.

I'd love to know if there was a mechanism that actions when the engine is accelerating/engine braking and also actions when the handbrake is on/off.