Faulty Speedo Need Xm Mechanic

[echo]

My speedo doesn't work and having looked at the Haynes it's not the sort of job I can do, I don't have jacks/ stands to get under the car safely to check the cable. can anyone recommend a Citroen mechanic in North London?

It looks like there are a few mechanics on this board, are your details all posted somewhere?

thanks, MW

[Peter.N.]

Is it a Mk 1 or 2?

Peter.N.

[echo]

mark2 1996 P reg. The previous owner said it just needed a new speedo cable.

[xmexclusive]

Hi Echo

I am certain that a P reg Mk2 will have a electronic speedo not a mechanical cable driven one. Does the trip & mileometer still work? If it does then it is the speedo head at fault not the cable. If nothing works then it is most likely the sender box on the gearbox that converts the mechanical drive into an electrical signal. It is seldom the electrical cable at fault. New sender boxes are around £40 and on the smaller engined XM's not too difficult to get at. For the first few years of Mk2 production Citroen were still fitting an older type of sender box that is prone to letting water in with the electronics. The senders are just held in place by a single 10mm bolt. The plastic drive cog is a push fit in the sender and has to be reused in the new one (each model of XM has a coloured plastic drive cog with a different number of teeth to make the speedo give the right speed). The later senders fit without modification. New speedo heads are expensive so best to find a good secondhand one if it comes to that.

Regards

XMexc

This post has been edited by xmexclusive on December 12, 2007 07:14 pm

[Peter.N.]

The sensor is mounted just above the o/s driveshaft where it enters the diff and as XMexc says it is not to difficult to get at, it is only held in by one bolt. The problem I have had with one of mine is in the wiring to the red plug in the instrument panel, not making contact with the pins, but I would make that your second line of investigation.

Peter.N.

[echo]

the trip and milometer don't work so it could be the sender. Does the electronic cable come out of the sender and go straight to the dash, I have a feeling the guy who sold it was trying to screw around with the milage. Hopefully he just disconnected the cable somehow.

When you say an electronic speedo you are talking about how it's driven right? It's got a needle and dial and not a night rider style electonic display.

This post has been edited by echo on December 12, 2007 08:17 pm

[noz]

Hi Peter,

You're a dark horse. I didn't know you were the keyholder for the solution to the dodgy speedo's

My speed has been giving me grief for almost a year now. I've had the dash out 3 or 4 times the most recent case being last weekend. I have been over every square mm of the little pcb behind the speedo looking for a dry joint. If I give the dash a thump the speedo springs back into life, at least for a little while. That gives me the confidence I'm looking at a joint problem. The trouble is I can't find the little £$%&*^(.

At the weekend I jacked one wheel off the ground put it in gear and ran the engine whilst the instrument cluster was in my hand but still connected to the car. I tried every test I know including putting a scope on the pulse signal. Everything was OK including the speedo needle. Whilst out, the speedo worked fine. I put the dash back together and it worked fine on my return journey to Muir of Ord on Tuesday. However, I jumped into the car this morning to go to work and its dead again.

It never dawned on me to suspect the red multi-pin plug. They look pretty good quality with a smooth plug-socket entry and a nice snap-fit lock.

How did you determine that the red plug was at fault. Was it a visible fault or did you find it with a meter? I'm very curious because if I think there's a chance thats my fault too then the dash will be back out before you can say LHM.

Cheers

noz

sorry to hijack your thread echo.

[Peter.N.]

Hi Noz

This has been an ongoing problem with the red one that my son drives, initially it was intermittent, as was the fuel gauge!. I replaced the sensor (speedo) but it was still intermittent but it was as a result of eventually finding the fuel gauge fault that (I think) I have found the speedo problem.

The fuel gauge problem I eventually found was due to an intermittently missing 12v supply to one of the pins on the green plug, not knowing from whence it was fed, I strapped it to another 12v supply, which according the Haynes came from the same source, and it was cured.

I have had numerous attempts to solve the speedo problem but it has always returned to intermittent mode, until, the last time I took the panel out, or to be correct, pulled the red plug out. Because the panel was still in situ, I had to bend the wires to the plug back hard against the plug making a sharp right angle, after that, the speedo worked all the way to Lairg! It has now gone intermittent again but I strongly suspect that the wires into the plug are the problem. I also now strongly suspect that the fuel guage problem wasn't caused by a loss of the supply, but a bad connection into the green plug.

When it stops raining I will try and prove my theory and let you know the outcome.

Peter.

[noz]

Hi Peter,

Thanks for that. I'll do the same.

Cheers

noz

[DerekW]

Echo,

Ref Peter's comment about the sender unit being on the offside, on my, 2.0 turbo auto it's on the nearside. I think that either position will require major dismantling to get at from above but is easy when lying on your back below. Your best bet may be to buy yourself a pair of ramps, they aren't too expensive and often come in useful.

You may understand that long distance diagnosis is not easy, but it is extremely difficult when we don't know which model we're dealing with. Could I suggest that you append your details to your signature?

Derek

[xmexclusive]

Hi Echo

There is a white connector and plug in the middle of the cable from the sender to the speedo. In most Mk2's it can be found under the LHM tank in the engine compartment.

Hi Noz & Peter

The plugs in the dash display connections have good quality IDC connections but the discrete wires used are much stiffer than used in normal electronics IDC ribbon cables. Have a care not to force open the contact cutting teeth if you try to remake the connections. A look at an unused contact with a magnifying glass shows the position of the teeth. I have never found a loose wire yet but one that has come back out the cutting teeth will be easily spotted though it is not likely to cause an intermittant fault. It is possible that poor IDC assembly of the odd wire has cut all the conductors as well as the insulation. This is much more likely to cause an intermittant fault. Visual examination will not reveal this as the wire will look well seated in the cutting teeth and be held firm by the plastic wire lock hooks moulded into the plug body.

Regards

John

[Peter.N.]

Hi Derek

I don't think that I said that the sensor was on the o/s, I think I said that it was where the o/s driveshaft enters the diff - putting it actually on the n/s.

John

Your comments noted. I was going to try and solder the connections if accessable, that was what I did to restore the 12v supply with a link, you do need a soldering iron with a very small tip though. I could of course be completely wrong, but the evidence seems to point to the connectors.

Peter.N.

[echo]

unfortunately I live on a hill and would have to drive to somewhere flat before I could safely get under the car. I'll see if I can get to it from the top otherwise I'll try and find a mechanic.

[DerekW]

Hi Peter,

If my eyes get any worse I'm going to have to give up driving.

Mr Magoo