Preheat relay timer not working

paul in normandy · Unread post by **paul in normandy** » 16 Feb 2010, 21:24

Looks as if I was repeating myself again!
Back to the breakers this morning - yet another relay - same result!
Plan B beginning to look a very attractive proposition now - have to have a rummage for a suitable switch, always used 2cv brake fluid level ones for this sort of purpose in the past, the distant past that is

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Unread post by **CitroJim** » 16 Feb 2010, 21:35

We need a wiring diagram!

It must be something else affecting it and it must be to do with post-heating but without a diagram, it'll be hard going...

paul in normandy · Unread post by **paul in normandy** » 17 Feb 2010, 06:50

Going back to UK in our BX this pm, have managed to acquire a copy of the Haynes manual so might try and work something out from that.
A friend here is good with vehicle electrics so might try and rope him in as well.

paul in normandy · Unread post by **paul in normandy** » 22 Feb 2010, 14:28

Got a copy of the Haynes manual - and guess which wiring diagram is not in there - the one for the glow plug relay.
A friend suggested it might be the earth connection out of the thin wires that control the box, sound likely?

paul in normandy · Unread post by **paul in normandy** » 16 Apr 2010, 18:46

Have attempted to put plan B into operation, by completely disconnecting the existing relay and wiring them up directly to another relay via a 2cv brakefluid level switch.
The 'new relay' clicks but still no go.
And here was me thinking the difficult bit was going to be getting the wire through the bulkhead!

paul in normandy · Unread post by **paul in normandy** » 09 May 2010, 10:30

Have fathomed out the wiring on the plan B relay, and for the sake of safety have wired it through a fuse box - so far its blown a 25 amp then a 30 amp fuse - anyone any idea what size fuse it should have?

Xantidote · Unread post by **Xantidote** » 09 May 2010, 16:14

Hi Paul,

Have been following your thread with interest, over the months you've struggled with it. Always interested to learn what the problem was, and how it was finally solved.

You ask about fuse rating for Plan B. If this is for the operation of the relay itself, then it shouldn't be taking much at all - only a few amps (I've measured an "ordinary" citroen relay that I used to do the headlamp mod on my Xantia, and it was less than 1/2 amp). A starter relay may IMHO take a few amps.

However, if you're talking about a fuse in the actual feed to the glow plugs busbar, then based on my Xantia, I'm not surprised the fuse has blown. IIRC, Haynes suggests a current draw of 15-20 amps per glowplug. Sometimes, to check glowplug operation, I measure the current drain with all 4 glowplugs connected, and this gives about 70 amps falling away as the glowplugs heat up. If your glowplugs draw the same current, then you have the answer. Hope you've used a thick enough cable

spider · Unread post by **spider** » 09 May 2010, 16:18

I was not aware they were actually fused (the bus bar feed itself) , on older PSA models they are usually not, (apart from the thick 'shunt' link in the battery positive unit)

I would guess newer models use the 60 or 80 amp fuse for them (the 'extra large' spades), the engine bay fusebox.

I do not have anything here to actually check so I'm going from memory, certainly my 205 only has the huge shunt in the +VE unit next to the battery.

paul in normandy · Unread post by **paul in normandy** » 09 May 2010, 16:55

Wiring is basically thus
relay activation - connection to battery wired via 5 amp fuse to switch (old 2cv brake fluid level push to make switch) back to relay contact no 86 then via relay contact 85 to earth.
glow plug activation - wire from battery to relay contact no 30 via relay contact no 87 to fuse box, then to common contact with glow plug bus bar on preheat relay.
At the moment to get the car to start its necessary to connect the common contact on the glow plug relay for the bus bar to the positive side of the battery using a thick wire with a loop connector on the end - not really ideal!
Is it possible / safe to do away with the fuse on the glow plug activation side?
I made sure I used thick cable for the glow plug side of the installation.

Xantidote · Unread post by **Xantidote** » 09 May 2010, 18:02

Paul,

My S1 Xantia has no fuse on the feed from the relay to the busbar, though I suppose there could be some sort of overload protection within the control box itself. Every fuse presents a potential voltage drop, and will become more of a problem as the car ages and corrosion sets in.

I presume the "new" relay is fairly close to the existing control box, thereby minimising the length of the new thick feed cable, and attendant risk of chafe and shorting out.

paul in normandy · Unread post by **paul in normandy** » 09 May 2010, 18:52

The 'new' relay is right next to the old relay.

paul in normandy · Unread post by **paul in normandy** » 23 Jun 2010, 16:21

To bring this up to date.
Have got the preheat working through the additional relay and ex 2cv switch, but there is one odd anomaly, if I press the new preheat switch before turning on the ignition the warning light acts normally and goes out after a few seconds, however if I turn on the ignition first the warning light goes on, then immediately off.
Still at least I don't have to open the bonnet every time I start it from cold anymore!

spider · Unread post by **spider** » 23 Jun 2010, 17:13

Might be a back-feed into the post heating circuit or something.

If its not causing problems now, leave it.

You could disable / remove the post heating stuff its not really essential anyway (I threw away my timing advance module too without any ill effects apart from a slightly smelly exhaust at idle when stone cold)

But if its not causing problems, 'as-is' is OK

Unread post by **DHallworth** » 24 Jun 2010, 14:16

I am having this problem with a Xantia HDi.

The glow plug light comes on for literally a second and goes off very quickly.

I've replaced all 4 glow plugs, this made no difference and the car was still a bit smokey on start up.

I then replaced the glow plug control box with a genuine Citroen item, tried it again and it is still doing the same thing.

I tested all 4 glow plugs that I removed and they all tested ok.

I'll follow this with interest!

David.

paul in normandy · Unread post by **paul in normandy** » 24 Jun 2010, 14:41

I won't be pursuing it further - mine works now, although not as it was designed, but as it was a freebie I'm not spending any more on it - a sentiment a scot would concur with I suspect!