Glow plug relay fault? C4

[dohageorge]

Hi,
I have a C4 VTR+ 1.6hdi on a 57 plate.
I had an injector leak and the cars been off the road for a couple of months whilst I cleaned it up and had the injectors refurbed.
Now it's all back together I have a wierd fault.
My electrics, dashboard, radio, lights, door locks, don't work if the glow plug relay is plugged in, something seems to be shorting when I put the relay in. I've bought a new relay but it's still the same.
I have removed the connectors from all 4 glow plugs, no change.
I removed the glow plug loom, there's a connector near the glow plugs, no change.
I removed the 4 injector connectors, no change.
Looking at the electrical diagram for the ignition/preheating I see the glow plug relay item 1158 is connected to an ECU, item 1320, and also BCP3 which I believe is the '3rd protection relay switching unit'.
My question is this, where on earth is BCP3 physically located? I want to unplug it to see if my fault goes away.
Hope someone out there can help.
George.

[Xantidote]

My electrics, dashboard, radio, lights, door locks, don't work if the glow plug relay is plugged in, something seems to be shorting when I put the relay in

What makes you think there's a short - has a fuse blown? Does it do this when the key's not in the "ignition"?

Think back to what you have disturbed since the engine last ran.

Maybe I'm on the wrong track here, but I'd also question if it might be the battery. Could it be the original, and it's now reaching the end of it's life after receiving no charge for a couple of months? I've read on FCF that the C5 needs good battery voltage, and doesn't take kindly to batteries beyond the prime of youth, and maybe the C4 likewise. This wouldn't explain things if the electrics fail as you describe, when no key's in the ignition. Another option might be a poor earth somewhere?

[dohageorge]

Hi,
With the relay out, my dashboard works, the radio works the doors lock etc.
I put the relay in and I lose everything, I don't have to put the key in the ignition.
That's why I think it's a short. I just want to isolate the relay from BCP3 to see if I'm on the right track.
I've removed all the connections to the glow plugs and injectors, I dont have the fuel filter or air filter connected either. I don't think I've had anything else off. I've had the car from new and it hasn't been used much in the past year so you may be right about the battery. I'll see how much a new one is. Thanks.

[Hell Razor5543]

The later Citroens (with all their electronics) can be sensitive about batteries. All sorts of weird things can happen (well, the C5 is known for this). At least, if you pop a known good battery in you can see how it goes.

[myglaren]

The Battery Guys seem to have a decent reputation for prices and delivery times.

[citroenxm]

Id strongly advise against changing the heater plugs... this is because they are known to snap off in the head!!

The 1.6 will always start without heaters anyway.. How do I know about the heater plugs??? Yes, been here!

[Peter.N.]

Connect a meter across the battery and watch what happens to it when you plug the relay in.

Peter

[Xantidote]

My thinking is that when you plug in the glowplugs relay, it creates a little extra load on the battery (though not much, as you're not energising the glowplugs), and the voltage drop is just enough for other electrics to play up/fail. As Peter suggests, voltmeter across battery. You could try a higher current demand by switching on the lights/headlights, leaving the glowplugs relay disconnected, although if the battery is knacked, I wouldn't want to be responsible for sending your electronics haywire

As Hell Razor suggests, try a good battery if you've got access to one, before buying a new one

[dohageorge]

Hi guys,
thanks for all the useful ideas, I drive a volvo (company car) so I can take the battery out to try, I'll also put a meter across the old battery and see what happens with all the suggestions above. It'll be a couple of days before I get home and try this but thanks again, I'll let you all know how I get on.
G.

[Xantidote]

If it comes to taking the battery out of the Volvo, an option , if you can get the cars close enough, would be just to use a set of jump leads. This would remove the risk of the electrics playing up on the Volve when you refit it's battery. Wouldn't wan't you to have 2 cars with weird electrics

[dohageorge]

Hi,
put the volvo battery in, no change in the fault. Put all the cables back together, cleared all the faults and turned the engine over.
Still have my original fault codes, 1351 (Preheating relay cct relay supplied and plugs never supplied) and F8EB(Absence of permanent +ve on display)
getting quite frustrated now. Looks like my next move is the ECU unless someone can tell me where BCP3 is located?

[Xantidote]

Oh dear, sorry to hear problem's still there . My knowledge of the C4 and modern car electronics is minimal, so I'm not going to be much further use. Hopefully someone more knowledgeable will be along with more ideas.

[dohageorge]

Hi Martin,
thanks for the help anyway, any advice appreciated.
George.