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280SL Speedo Sending unit.

11K views 68 replies 14 participants last post by  grahamandbea 
#1 ·
'83 280SL 5 speed. Speedo and odo were working intermittently. Then all are dead.

Anyone know where the elec. sending unit for this one is? Trans? Dif?

Also could the problem be in the head unit. Any fuses on this circuit? I don't have the cd or EPC on this puter.
 
#44 ·
item 6 is a hot wire that runs the clock
item 3 is the connector for all the other gauges (fuel,oil press,water temp) and possibly tach
item 5 ...not sure usually the connector will match
in looking at the first pic you had...it looks like your speedo connector may not have the plug attachment any more and could be grounding/shorting ifit's not shielded
 
#46 ·
all the connectors on the back of the cluster have components that hook up to them that i'm sure of. but what i'm not is how the speedo works. on this model doesn't the speedo connect to the trans in some way? maybe since its a euro version its on the passanger side of the trans instead of the drivers. quessing
 
#47 ·
on my 280SL 5 speed the transducer for the speedo is on the passenger side the power for the speedo comes in on the plug that goes to that circuit board...the impulse for the speedo comes in thru that single connector that you identified....I still think your problem is a worn out gear in side the speedo cluster...
 
#52 ·
either way the speedo went out and i'm searching for a speedo meter to replace it to see if that works in the mean time i'm trying to figure out the speedo cable which is why i'm on here. usually i would find the cable on the trans but instead i find a vacuum on the drivers side which is where i would usually find a speedo cable hook up. thats what has me confused on if its partial electric/vacuum?
 
#55 ·
Not sure, but either you have a mechanical speedometer in which case you have a cable or an electrical speedometer in which case you have a sending unit... You have an electric speedometer, ergo, there should be a sending unit.

Regardless, I'm confused as hell. Which car do you have, as well as the chassis number. If you're unsure of the chassis number, it will probably be the first 3 numbers of the VIN.

Since this is the 107 forum most information you get will at best be an educated guess, with more accurate information in the correct chassis forum.

BTW, It's always helpful if you fill out your profile.
 
#56 ·
the back of your cluster is marked 280sel, the port you are calling 1 appears to be for your economy guage wich is vacuume, which means you have an elec speedo/odo and go to the 116 forum where they are more informed than us, Oh, I see you did and nobody responded!
 
#57 ·
the vin starts out with the #'s 126 so i'm gonna take a stab at it and say its a w126 which is how most people on here refer to them as, and i will update my profile haven't gotten around to that just yet. thanks for all your help guys this is the first luxury car i've gotten my hands on and want to keep it. i've had POS's in the past but this is the first car that is in great shape and is awesome. can see why everyone loves these cars. they ride smooth and look great.
 
#58 ·
#2 is the connection for the vacuum for the economy gauge. 1 is electrical.
All of the connections should be obvious.
You have not located the speed sensor. For all I know it is on the differential instead of the trans but it is definitely not operated by vacuum.
 
#59 ·
the one i call the speedo connector is exactly that, its and electrical male connector and not a vacuum line. the vacuum line is on the right, on the silver bar, under the round set of male pins. the speedo is electric i have determined that much but i can't seem to find the speedo cable which is my problem, the guage went out and i can't figure out where its located. the line on the trans is a vacuum line and as someone else has posted there is a speed sensor on the trans as well which i can't see, what i can see is a back up light lock out relay and the vacuum line. i want to try and find the sensor or what ever it might be and try to fix that while i am searching for an adaquit speedometer
 
#62 ·
On the back of the cluster, #5 is your tachometer connection. Many people have cleared problems by attaching an extra ground lead from the cluster to a steel part of the body behind there. Be carelul of clearances and moving parts. (Not sure if the 126 has the wiper linkage under there, but the 107 does.)

Good luck.
 
#64 ·
Attach it to the tach metal backplate and a good ground on the body, you can do a search here to find how many problems it has resolved. Also I did a search in th 123 forum and there is a lot of info on speedo problems and solutions, but I wouldn't want to take the learning experiance away from you.
 
#65 ·
alright guys got my new speedometer into the mercedes and still no change thought it might have been the speedometer so i got one real cheap $65 so i think it may be the transmission wiring harness that has the speedo sensor on it. the dash now lights up where it didn't before but i'm starting to get lost on the whole thing. any ideas
 
#67 ·
According to my friend in the trade the 2nd picture in post #61 is the speed sensor, we had mine up on the lift this morning and there isn't anything else down there so it has to be it.
What makes you think it has a vacuum connection? I know it looks like a hose but is it not just a well protected cable?
To operate as a speed sensor it has to be on the output area of the box to measure the speed of the drive shaft so I think it has to be this item.
 
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