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Matt
Matt, Engineer
Category: Mercedes
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Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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My rev counter suddenly increases without engine revs doing

Customer Question

my rev counter suddenly increases without engine revs doing so.A fist banged under the instrument cluster resets but not for long,,the solution is ?
Submitted: 9 months ago.
Category: Mercedes
Expert:  Matt replied 9 months ago.

Hello

1st thing to try is to disconnecting the instrument pack from tthe wiring loom and spray both halves with some switch cleaner,

also trace the wiring loom back from the cluster checking for damage to the insulation and hard sections of wire

if this doesn't help then I'd say the instrument cluster will have to go off for repair

try this firm:

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http://www.zingelectronics.com.au/ecu-and-ecm-repairs/s36286

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Expert:  Matt replied 9 months ago.

Hi

do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you

Customer: replied 9 months ago.
why does rev needle go down when instrument cluster hit from below and up ie shows higher revs when struck from above,please.
Expert:  Matt replied 9 months ago.

Hello

Ok in that case I'd suspect the instrument pack is faulty and needs repairs to the rev counter or just replace the whole thing

http://www.zingelectronics.com.au/ecu-and-ecm-repairs/s36286

Customer: replied 9 months ago.
when you say instrument pack replacement are you referring to rev counter only or whole instrument panel,one sounds pricy the other v expensive,any clues? repair of rev counter seems the way to go.How does this work,surely it is all electronic with this influencing the rev counter,not some rotating bit of wire.Is getting the instrument binnacle out easy.Any ideas on time and cost please.
Expert:  Matt replied 9 months ago.

Hello

the instruments aren't separate , rather its all 1 unit

and the needle is driven by a small motor inside the pack thats in turn controlled by its own control unit

so I'd say its best o get in touch with the electronic specialists

Expert:  Matt replied 9 months ago.

Hi

do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you

Customer: replied 9 months ago.
Hi Matt,am I correct in that a faulty rev counter,rather than poor electrical contact,can only be sorted by replacement of all instrument panel.Since tapping panel above the rev counter increases rev counter needle and tapping below decreases rev counter to zero ( after several taps) does this indicate faulty guage or faulty electrical connection.Cost to restore function will determine my course of action.
Expert:  Matt replied 9 months ago.

hello

you are correct, if the panel connections are good then either the instrument cluster has to be repaired by a specialist or replaced entirely

the most economical route is to source a good used cluster and have it re-programmed by the dealer

try

http://www.mbspares.com.au/

I'd estimate about $100 for a cluster and then 1-2 hours labour at the dealers

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