speedometer and tach stopped working at same time?
 

My car is a '95 SL500. What could cause both the tach and speedometer to stop working immediately after replacing the old battery with a new one? I looked at the positive wiring connections and don't see anything unusual. This is a struggle to remove and replace the battery in the '95 SL500 because the working space is confined in the trunk. The wires had to be "bent" out of the way to lower the new battery into the trunk cavity. Is there a fuse or a "hot" wire that connects at the battery? I assume this has to be a loose connection or I blew a fuse in the process of "jumping" the battery to start the car. The battery never went "dead-dead", just not enough juice to turn over and drive over to the AutoZone Parts store.

Any ideas? Thanks Steve

Have you checked fuses in the BASE module in the computer box?

tach and speedo failure
 

Thanks Doc, No I haven't, I was hoping someone with the expertise would send me in the right direction before I started pulling at wires and such. There isn't any check engine light on or anything else that might throw a code. I thought it would have to be a blown fuse somewhere or a loose wire that I can't see.

Let you know after I've had a chance to look, Happy Easter, and thanks,

Steve

tach and speedo stopped working after battery exchange.
 

Doc, Today, I checked all of the (4) 10 amp fuses in the main computer bank, the fuses in the trunk and the standard fuse box and the (2) fuses where the "other" relays are located behind the drivers side fuse box, but none are blown. Rechecked to see if any other "hot red" wires were affected when the battery was exchanged but nothing looks out of sorts. I cleaned and re-tightened as many ground wires as I could find in the engine bay, but still no tach or speedo.

Do you or anyone else have any additional thoughts where I should be looking? I can't believe that this sort of thing (tach and speedo) quit and no one else has had this happen to them. Where does the signal (power) in this case originate to activate the tach and the speedo? Since I was looking for a shorted fuse, I didn't see anything listed per se for speedo or tach in all of the fuse arrays I looked at.

Thanks Steve fazekasstephen@gmail.com

Is the ABS traction lamp on?

Speedo and Tach quit working after battery exchange.
 

Doc, The Traction Light is not on. Here is more background info: '95 SL500, Three yrs ago, I changed all of the usual problems with wiring harnesses, the Main harness, alternator/starter harness, had BBA Reman rewire the ETA (throttle) wiring, also replaced abs sensors and related wiring on front brakes. This car had been running fine. The battery was about 7 years old before it failed and I replaced it on Friday last week. Now this, thanks for your help and follow-up. I'm stumped because I don't know where to start looking beyond fuses. The dash hasn't been out of the car and I don't know how much trouble I'd get into if I tried to "push" it out and attempt to check and see if I was getting "juice or a signal" at these two gauges, and then work my way back, but to where I don't know. I thought you'd might like to take on a challenging case ala Dr. Quincy ME.

Thanks, Steve

Since the traction lamp isn't on, most likely the problem is in the cluster itself.
Does the top still work?

Doc, The hard top is still on the car, its 36F this morning in Cleveland Ohio. Would "releasing" the top for removal (but not actually taking it off) give an indication if the top mechanism is working? I just had a thought, since the battery was removed, do I have to re-sync the door windows so the top will work properly before I attempt the top activation? If the cluster failed, do you recommend any business in particular to send it for repair? There's a ton of places for GM and Ford but I haven't looked for anyone that repairs MBZ cars from the '90's.

Thanks a million, Steve

speedo and tach failure
 

Doc, More info. I just took the car for a drive. The odometer works, the trip mileage indicator works, the cruise control works, the MPG gauge is working, the lights on the dash and all of the other gauges work.

Is there a tach signal generator somewhere. Where does the speedo receive its info to display? Should I be thinking of "pulling" the cluster at this point?

Thanks, Steve

speedo and tach stopped working
 

Doc, The Top functions. I released the hydraulic locks and the windows all worked in sync., I didn't remove the hardtop but it appears the system works. I also checked the major fuse metallic strips located in a covered housing behind the power brake booster near the firewall and three fuse strips were intact.

Your thoughts, Steve