Hi, I just had my rolling tach repaired by Redline Gauge and tach repair. I am confident in his work, so I don't think my problem is from his work. What I need to know is how the L-shaped plug in the back if configured. I have seen nothing but brown on top and pink on bottom photos of this plug. Since you can only plug an L-shaped plug in one way, why is mine pink on top and brown on the bottom. Could the connectors be possitioned wrong, so that the "L" is now inverted? My whole reason for searching this out and asking the question is that when I put the tach back in my cluster and reinstalled my dash, the tach reads normal at idle, and revs up to 2,000 rpms and that is all she wrote. It won't rev any higher. It is hooked up to a stock GM HEI unit with a 4 connector module. Would the wiring being backwords allow the tach to work a little, but not accurate, or would the wires being on the wrong connectors cause it to not work at all. Thanks for the help. I have tried everything I could think of including checking the voltage to the pink wire, checking that it is grounded well, all the fuses, etc.

Thanks. :confused:

See the pic. The top terminal is the brown, pulse signal, the bottom is the pink, +12 V. If your tach is wired correct the problem is with the tach. You can remove it and carefully move the pointer past the 2000 position, checking for a mechanical binding.

Thanks for posting the pic. I can't, due to the fact that the tach is in the car at this point. However, I can see it up under there and I know for sure that the two arms on the connectors are pointed in the other direction from your photo making it, ( when plugged in ), 12V on top and tach pulse on the bottom. The plug will only go on one way. So the internals are put back in backwards or the repair man put the connector arms back on in the wrong direction. Either way, is it possible to even get the tach to move at all if the pulse signal is connected to the 12V connector and the 12V wire is connected to the pulse input connector? Also, the needle does go up to at least 4K, because yesterday it was bouncing from idle up to 4K sporatically until I put in a homemade tach filter that was on a post by JimM a while back. It calmed it down so it no longer goes crazy, but it won't rev past 2K any more and never really did with actual revs. It was just spastic. If anyone knows if this thing will operate half way with the plug on backwards, let me know. I will remove the tach and reposition the arms so that the plug connects correctly. If it would fry it, I don't want to chance it.
Thanks again,

Michael :confused:

You can switch the position of the wires in the plastic connector. I'm surprised it will work at all with the signal and power wires backwards. If anything were going to be damaged by how you connect power and pulse, it would already be damaged.

my best guess is that you don't have a GOOD ground to to the housing !!!

P.S. quit screwing around those things are EXPENSIVE !!!

Elree, it's the only thing left to try. I searched every post on the subject for the past 8 years and have never heard of this situation. I will try switching the wires in the plastic housing as you suggest. It is a lot easier than removing the whole enchilada and repositioning the spade terminals.
Mark, believe me, I know how expensive they are. I have tried running grounds everywhere possible. ( I think my dog still has one soldered to his collar) LOL. No change, in fact, evrything on the dash works fine without the ground wire at all which is kind of weird. There is only the one thing left to try and it is definitely plugged in 180 degrees different than any other I have seen.
Thanks guys for responding and if you think of something else, please let me know.
Michael. :yes:

Success! I got up under the dash with a mirror and discovered the wires were indeed connected to the wrong terminals. I switched the wires in the plug thanks to Elree's suggestion and fired it up. The tach came to life for the first time since I have owned the car. I guess now we know that a tach will partially function even when plugged in backwards. Thanks so much for the input. Hey, my headache is gone :-)

Michael :hurray:

By the way, John at Redline Gauge and Tach repair is top notch. He does excellent work and if you have a problem or a question, he is more than happy to spend time with you. He also recalibrated and refaced my instruments and they came out looking like NOS. Very satisfied.