Explosion and smoke when pulled handbrake on...

rashmore · Post by **rashmore** » 04 Jan 2005, 13:56

Whilst en-route on a shopping trip yesterday, I pulled the handbrake on. As it reached the top there was a loud bang, like a shot gun going off, and the cabin filled with acrid smoke.
I was left with an un-operational handbrake - it just moves up and down. There is rachet clicking but no tension / resistance when pull it up and therefore no brake effect. No light comes on when lift handbrake
The smoke was eminating from the handbrake mechanism cover. I remember there being a box with wires attached on my last zx(1.9d) linked somehow to the handbrake but not looked under cover on this one yet.
Will look/strip tonight if force 10 gale subdued, but any thoughts what it might be ?
Nothing hanging out underneath but I know the hand brake cables are worse for wear externally (hence new ones in garage) but didn't think that this little box would effect handbrake.
I'm guessing its this box but what else does it do besides the light ? likely to be expensive, same on all models [xx(]
TIA

NiSk · Post by **NiSk** » 04 Jan 2005, 14:50

Could be that excessive movement of the handbrake mechanism (like when the wire broke) caused a short-circuit in the handbrake indicator circuit giving acrid fumes of melting plastic? . . . or a plastic-coated handbrake wire falling on a hot exhaust pipe? . . .
As far as I know there's no pyrotechnic pretensioner anywhere near the handbrake on the ZX.
//NiSk

IanR · Post by **IanR** » 04 Jan 2005, 16:48

Don't know about the ZX, but the Xantia's seatbelt-pretensioner control box is in there. Might be the recoil from the cable breaking subjected it to shock-forces that seemed like a collision, so it fired. Or the overtravel on the lever cut the wiring, or suchlike.

VLL · Post by **VLL** » 04 Jan 2005, 17:25

Sounds like the pretensioner to me, they are down by handbrake and they are known to go off unless one of the recalls has been done. If you look under the bonnet on the left hand side behind the headlight there should be a small sticker with the citroen logo and a tick and a number (cant remember the number off the top of my head, will look latter), which would have been applied if the recall modifications were done.
I do remember getting it done to mine a long time ago.

rashmore · Post by **rashmore** » 04 Jan 2005, 19:00

Just had a look for sticker - silver about 1inch square with XB2 XB3 R1995/64 and a tick on it, so guess the recall was done.
Will pull apart tonight to see what else is broken as no hand brake at all - either both cables gone or part of mechanism itself broke. Price up new pretensioner from citroen - would u get one off a scrapper ? (look for sticker) or consider that a little risky

rashmore · Post by **rashmore** » 04 Jan 2005, 19:22

Ouch - new one is around £90 (need to supply chassis number to get exact type) time to try scrap yard ? Would it be the same on a 306, other citroens (will ask cit when call back to confim type from chasis no) ?

IanR · Post by **IanR** » 04 Jan 2005, 22:30

When fitting, remember to treat as an explosive device, i.e. avoid any risk of electrical contact (including static) whilst handling. (but then I guess you would, after your experience anyway!)

rashmore · Post by **rashmore** » 05 Jan 2005, 15:19

Lol
Had a quick look last night. Removed handbrake cover, everything appears fine.
Cables move in and out, t bar connector fine, racket ok (therefore problem lies further back underneath - wierd if both broken at same time).
No evidence of explosion in this department (yellow box next to hand brake appears fine). Need to determine what this is so can test. All wiring suitably insulated with no evidence of damage
Checked fuses under steering (couldn't find any under bonnet) and all appear fine, so why do i not get a handrake light when ignition on ? will have to check switch and then wiring diagram to see what else in that circuit.
Looked at the haynes book of lies and need to remove seat panels to examine pre-trensioners, not a job to be completed using just a head torch in the freezing cold.
How do i know if one of the pyro technics have gone off ? will there be some form of indicator ? can then look at second hand one then
Can't test in any way electrical as that will trigger device and then will defo need replacing.
Cheers

NiSk · Post by **NiSk** » 05 Jan 2005, 15:59

Can't find anything in any of my Haynes manuals for Citroen/Peugeot concerning seat belt pretensioners - they seem to have conveniently forgotten them. However, in my Audi A4 Haynes they mention that the pretensioning device is at the bottom of the C-post and that once activated, the inertia reel is completely locked. I've no idea if the same applies to your ZX (or my own XM for that matter - but I had a feeling that they were located in the seats?) but I would have thought that the inertial reel being locked would apply in any case?
//NiSk

PowerLee · Post by **PowerLee** » 05 Jan 2005, 16:25

The ZX & XM seatbelt pretensioners are built into the seat belt buckle assy.
Have a look at both seat belt buckles, Is one about 4 inches shorter then the other in height?
Are the both very short?

NiSk · Post by **NiSk** » 05 Jan 2005, 17:04

Thanks for that info, PowerLee - makes me even more dubious about poking around with a multimeter to try and find out why my heated leather seats don't work . . . (the car has side collision bags in the sides of the seats as well! a real pyrotechnic nightmare!)
//NiSk

PowerLee · Post by **PowerLee** » 05 Jan 2005, 17:46

The heated seats plugs are normally BROWN.
Find a wiring diagram & that will tell you which plugs NOT to play with!
Its most likely a burnt out element in the seat base.
Ive fixed them before on my 405 & its a right sod of a job to do.

rashmore · Post by **rashmore** » 05 Jan 2005, 17:49

My haynes book of half truths shows a picture of the assembly (hidden under plastic trim on seat by handbrake)Also the pyro control unit is in the centre console apparently ( Mr H), so i still do not know what the yellow box is by the handbrake
Belt buckle, rotating cam and discharge piston assembly for pyro part, all one item.
currently ( if memory serves) Passenger and driver buckle heights look the same, with cam position ready to rotate and tighten seat belt (viewed thro gap in trim can see groove in cam where buckle wire would be routed during rotation. buckles seem no lower than normal
Presumably if they had gone off , these would be rotated and locked in the shortened position ? If so this would be good news and hence the bang and explosion is related to handbrake wiring or cables themselves - tho it was a big band and loads of smoke...

explains no handbrake light

PowerLee · Post by **PowerLee** » 05 Jan 2005, 18:22

Yes
When the seatbelt pre tensioners go off, They will be locked in the short position.
The buckle position will be 4 inches lower then normal if they had gone off.

Post by **RichardW** » 05 Jan 2005, 18:33

>The buckle position will be 4 inches lower then normal if they had gone off.
Not to mention you'd be speaking in a high sqeaky voice where the belt had tightened across your groin....

)
I once melted a wire from the fuse box to the engine bay on a BX - it made a lot of white smoke - I was out of the car quick smart as I thought the whole lot was going up! I wonder if the bang was what ever part of the mechanism has given way (pulled the mount out of the floor maybe?) and then this caused the power wire for the handbrake light to short and melt its insulation, accounting for the smoke. It seems likely that there are 2 failures, as you have no handbrake, and no light, but the light is only operated from a cheapo switch on the floor, and has nothing to do with the efficiency (or otherwise!) of the handbrake.