Tach • The Dodge Challenger Message Board

by SF » 29 May 2001 2:47

Ok, I got the neg side of the coil heading to the terminal on the tach but where does the other side head. The schematic sort of indicates that it runs to the dash lights. This cannot be right.

by **dave-r** » 29 May 2001 18:35

Other side???

If memory serves me right (ok it has not got a good track record but bear with me) there should be 4 wires.

One goes to the negative of the coil (usually a green wire).

A second (Red?) will go to a 12volt source.

A third (black?) will go to earth.

And a fourth (white or yellow or something?) will go to the dash wiring so that it lights up when your dash lights do.

I think that should be right.

by SF » 02 Jun 2001 15:27

Nope. Memory is shot

This is factory. There is one line from the coil, and now, I found out the other goes to a ignition hot wire.

Thanks tho

by **dave-r** » 02 Jun 2001 22:08

Ah!
There yer go.
The factory one grounds through the case and illumination comes from above the dash so that logicaly only leaves the hot wire!!

by SF » 03 Jun 2001 16:57

Hahaha, yes, that is right. As of now, this tach does not work. So, I am not sure if I want it to work or if I am going to purchase an add on and mount to the column. Like we did in the '70's. That dash is not that easy to take out.

Thanks

by **dave-r** » 03 Jun 2001 20:14

Even when they work they don't work very well.

by **Von** » 11 Nov 2001 21:58

well, I am still having problems with all my wiring, and I have a rally cluster so I would appreciate my factory tach working so I don't have two tachs in my car. I will ask hans for the schematics but If someone could explain it so a "redneck" could understand I'd REALLY appreciate it. Oh, my gas gauge doesn't work nor my temp, but I'll do one thing at a time. I also have a wiring schematic I bought off e-bay but the sorry thing is not for a rally dash so it doesn't have a tach lead.

later

by **440six** » 12 Nov 2001 0:37

Von,
I just went through this on my '71 challenger. If you know which lead is the negative (coil), which I believe is the bottom extension on the tach, this needs to run direct to the negative side of the coil. If you can look under your dash and find the radio plug in (a non ralley dash will only have 2 wires running to it) the positive for the tach came off this. you can splice into this wire (red I believe) or simply buy you one of those crimp on extensions that will plug right into your radio plug (if you are not using the stock radio) and simply run it to the top extension on your tach. Is this clear?? Hope this helps. -Barry

by **Von** » 12 Nov 2001 15:23

I have no kind of radio in my car. Is this the problem or have I missed the point? every now and then it will flicker and bounce and things like that. So I need to check that the bottom lead of the tach goes directly to the coil and the top lead of the tach goes to something hot? is this correct??

by **440six** » 12 Nov 2001 23:51

Von,
I believe your wiring harness should have a radio plug in it regardless if the car had a radio in it or not. On 70-71 models (I don't know about 72 an up but would think it would be the same) you'll have a plug that looks like -]....one horizontal and one vertical plug in. There will be 2 orange wires running into one side and a red w/white tracer running to the other side. The red with the white tracer is your HOT wire. You can plug directly into that and run it to the top extension on your tach for your 'hot' wire. The bottom extension is the one that goes direct to the (-)coil. But, to answer your question, yes, any hot lead running to the top extension on your tach will produce the same result. As a matter of fact, the 72 and later challengers used the plug that goes into the flasher mounted above the brake pedal as the source for the 'hot' wire to the tach as opposed to the radio plug on the 70-71 models. As you can see, I know too much about this subject because of the problems I had trying to get mine working! -Barry

by **Von** » 19 Nov 2001 15:31

I spent all Sunday afternoon doing wiring on my car. heres what I came up with. I have a A-Body transmission wiring harness in my car for now. It's not the same. I think my tach lead from my gauge goes to slot #1 on my "block" that bolts to my fire wall. On an A-body harness that slot goes to my trans. I think that is the problem with my tach. right? now on to another thread for another question.

by **Von** » 19 Nov 2001 15:32

i didn't buy the A-body harness it was given to me. thats the only reason its on my car.

by **LITEMUP (Von)** » 09 Apr 2002 14:25

Dave you said in another thread just now that the factory tach was no where near right. I second that. But is there any thing that I can do to make it right? I dont want to have two tachs in my car and I dont want to buy one either(unless that is what I have to do). This summer I plan to take my car to the track so I need to have one that is reliable.

by **Dave-R (Roppa440)** » 09 Apr 2002 14:54

There are companies mentioned in other threads here that restore the instruments including re-calibrating the tach. I don't know how well this works though. I tried doing it myself on mine with poor results. I can't be bothered to take it all apart to try again.

by **Sf (Sf)** » 11 Apr 2002 18:51

I would be interested who rebuilds them too. I would send mine to them. I would not like taking the darn dash out again (twice) but it is just work.

by **Rob (Racer413)** » 12 Apr 2002 3:14

I use the factory tach and an autometer shift light. I only look at the tach at the start anyway.

by **LITEMUP (Von)** » 15 Apr 2002 14:39

I paid a total of $536 u.s. dollars to have everything re-callibrated and tested and fixed. last week my speedo just flat broke. my miledge still works so the cable works, just not my speedo. I will call them and tell them the tach and the speedo dont work. I sent it to Clock Doc in tennessee

how do you put a shift light on a factory tach?

by **Hans (72challenger)** » 15 Apr 2002 17:30

You need a rpm activater or something like that to install a shift light on a non-shift-light-equipped tach. I just bought a shift light too and thought I could connect it to my aftermarket tach, not... Now I need the so called rpm activater too, so if anybody has one or is able to get one, please let me know. I can't find one anywhere around here in the netherlands.

by **Rob (Racer413)** » 17 Apr 2002 0:28

Its a stand alone shift light. the rpm modules plug into it. It connects to ignition system not the tach. Either the negative side of the coil or ,in my case, the tach output on the MSD.

by **Hans (72challenger)** » 17 Apr 2002 8:26

Mine is a autometer shift light which is a replacement in cause the shift light on shift-light-equipped doesn't work anymore. But that wasn't said in the catalog otherwise I never bought it anyway. But I heard I can make it work on my tach (unknown brand) with some kind of activater so I just have to find something like that.

by **Dave-R (Roppa440)** » 17 Apr 2002 10:34

I am sure I have seen something like that in the Summit catalog.