400E - Tach Not Working
05-12-2015, 08:44 PM
#1
Super Member
Thread Starter
400E - Tach Not Working
Hello All,
I'm having an issue with my tach, it has been intermittent since I got it around 3k miles ago; it functioned perfectly over the winter although it seems to have now stopped working. I am aware that in many of the models the ovp relay is a culprit part, but my car does not have the ovp. I have yet to find anyone who is really sure as to what controls the tachometer on a 400E, if someone could please chime in with some insight it would be very much appreciated!!
I did replace the fuses under the hood. I read the speed sensor might have something to do with the tach, I checked it over and it looked to be fine. The engine harness for the car is good and was replaced not too long ago. This is all that has been checked so far.
Thank you!
I'm having an issue with my tach, it has been intermittent since I got it around 3k miles ago; it functioned perfectly over the winter although it seems to have now stopped working. I am aware that in many of the models the ovp relay is a culprit part, but my car does not have the ovp. I have yet to find anyone who is really sure as to what controls the tachometer on a 400E, if someone could please chime in with some insight it would be very much appreciated!!
I did replace the fuses under the hood. I read the speed sensor might have something to do with the tach, I checked it over and it looked to be fine. The engine harness for the car is good and was replaced not too long ago. This is all that has been checked so far.
Thank you!
Last edited by RPB; 05-12-2015 at 08:58 PM.
05-13-2015, 04:06 PM
#2
Out Of Control!!
I believe that I know how to get an answer for you, but hopefully when this is done you will be able to answer that question yourself--This all surrounds what is called the Electronic Accelerator Test---if you pulled the codes and you got a 10 you are on the correct path.
On the 124.034 the engine speed(TNA)signal comes from the base module(N16\1) and is displayed on your tach, however the test for a faulty signal is accomplished by testing pin 78 and 75 on the EA\CC\ISC control module---the correct voltage should be between 6-12 volts.
Hopefully this will dispel all the sausage over at kiddy benz----just the acts mam no HS!!
On the 124.034 the engine speed(TNA)signal comes from the base module(N16\1) and is displayed on your tach, however the test for a faulty signal is accomplished by testing pin 78 and 75 on the EA\CC\ISC control module---the correct voltage should be between 6-12 volts.
Hopefully this will dispel all the sausage over at kiddy benz----just the acts mam no HS!!
Last edited by Plutoe; 05-13-2015 at 04:09 PM.
05-16-2015, 06:39 PM
#3
Super Member
Thread Starter
Thanks for the help Plutoe! I did finally find a mechanic that was knowledgeable on my particular model. Your response to my question is spot on with regards to what he told me about the tach and where the signal generates. The problem is intermittent, it came back to life yesterday and then it just stopped working again on my drive home from work. This will be hard for me to diagnose, if you happen to know why this might be happening I would be very interested to hear your thoughts. Do you think that swapping the fuses in the module for new ones might have an effect? The module most likely has the original fuses.
Once again, thanks for your help!!
Once again, thanks for your help!!
Last edited by RPB; 05-16-2015 at 07:53 PM.
