SPEEDOMETER NOT WORKING!
Hi Guys,
Wonder if anyone can point me in the best direction.
The speedometer has stopped working.
It has done this intermittently before.
I checked the Electrical connection on the Central gearbox underneath.
All looked well.
What's the next most likely culprit please?
Thanks
Eljay
Hi your speedo is driven by a rotating drive cable from the transfer box to the back of the instrument.. the cable drives a dish fitted with a magnet in a drag cup... the faster it rotates the greater the movement of the pointer.....the right angled drive head on the transfer box has nylon gears which shed teeth if the drive cable gets hard to turn through lack of or hard lubricant..... if drive head is ok .... try to rotate the drive cable at the transfer box end with a reverse capable speed control electric drill and watch the indicator for movement... run the drill at SLOW SPEED and increase gently....if the pointer moves the drive is good. if not it is either a broken drive cable or a damaged instrument./....
I think you might find his vintage G has the later hall-effect sensor electronic drive with no cable :) Please see figure for a similar system.
Yes, it looks like that.
(But some of the diagram is missing off to the right?)
Where is the most likely trouble spot?
Obviously I'd like to check the lower end first because it looks more accessible?
How can I check its functionality?
Which fuse does this run off? (Though they all looked OK)
How difficult is sccess to the Dashboard rear?
Thanks
Eljay
Yes, apologies but it is not my diagram (copied off another website some time ago).
The instrument cluster is easy enough to remove, you might have to remove your steering wheel though (just 1 large nut, possibly 27mm, if you have the non-airbag version). The following page shows how, if you scroll down a bit:
http://www.v12uberalles.com/instrument_cluster_removal.htm
The tools they describe can be bought from many traders on ebay, or some people manage on their own with a pair of bent coat hangers. If you buy the proper tools they will work on a lot more MB models than just the G, in my humble opinion they are worth investing in, then again I like collecting MB-branded tools. Your dealer will be more than happy to supply you one (probably quickest route) if you give them the full part number:
W140 589 02 33 00.
http://cgi.ebay.com/ebaymotors/MERCEDES-INSTRUMENT-CLUSTER-REMOVAL-PULLE...
Thanks M2dxb
That looks a little bit tricky.
Before doing that can I check if it's necessary.
ie. Is there a test I can do at the Transfer Box end to rule out problems there first?
e.g. Are there 2 terminals on the box connector I can bridge for full deflection on the speedo....or something similar???
Thanks
Eljay
Hi sorry 1994 300 did not register with me (to early in the morning)...wipe the connector on the box clean and remove it from the socket clean the body pins and sockets of dirt and corrosion smear the rubber gaiter with petroleum jelly (vaseline) and replace...go for a drive and check for speedo reading. most probably poor connections.....
Hi there is still a drive unit and a sender down at the box... item 224 and 220 on the schematic.....either could be causing the problem..doubtful if it is at the speedohead in the instrument cluster......
Hi there is still a drive unit and a sender down at the box... item 224 and 220 on the schematic.....either could be causing the problem..doubtful if it is at the speedohead in the instrument cluster......
But I don't know that it is at the speedohead.
And I don't want to rip out the cluster unecessarily.
I've cleaned the connections on the box and they look good, but this didn't help.
How can I test the drive unit & sender on the box???
Thanks
Eljay
You're welcome any time.
Seriously removing the cluster shouldn't be too painful, if you were any closer I'd offer to do it myself...and if yours doesn't have an airbag it shouldn't be too difficult...then again I know it took me a while to do it first time round as I had an idea what these clusters cost new from the dealer. Sorry not sure of the latter bit, have you any good relations with a local merc specialist/dealer? It's a 2 minute job to check the wiring to the back of the cluster, and they might even do it for free...just a thought.
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The "Transfer Box" is the one under the centre of the vehicle with shafts in from gearbox and out to the diffs right?
I couldn't see a cable coming from this only a three-pin connector on the rear.
Where is this cable exactly please?
Eljay