E21 tacho retrofit issue, stuck on full revs

[danskiii]

Hi guys, new on this forum.
I have bought a 1977 318 E21 and changed the clock out for a tacho from a 320.
Now my problem is that when i fit the + and - wires from the clock it just goes up to full revs and stays there. I have also fitted a black wire that was not connected to anything to the "1" connection. Am I missing something or doing something wrong? Please help..

[dworthy]

Welcome to the Forum!

There should be 3 wires for the tach: Power 15 (Green/White); Ground 31 (Brown); Signal 1 (Black). You have the power going into the signal it seems, as the black wire should be coming from the dizzy or distributor.

Now is this a Injected M-10 or Carbs?

[danskiii]

Welcome to the Forum!

There should be 3 wires for the tach: Power 15 (Green/White); Ground 31 (Brown); Signal 1 (Black). You have the power going into the signal it seems, as the black wire should be coming from the dizzy or distributor.

Now is this a Injected M-10 or Carbs?

Thanks you
Im not quite sure whay you say 15 and 31, as on the tach it only says "+", "-" and "1". I have power on "+" from the clock, but that is red/white. Should i borrow the signal from the right connector where there is a green/white wire? Only the black wire was laying there not beeing used, insolated, when i removed the cluster..

It is with a single stock solex carb atm.

[dworthy]

Okay, no problems for you should use the correct color for the power, ect. It will keep the wiring diagrams correct so if you ever have to go back into the cluster, they will connected correctly.

The reason for the numbers is that's where it should be assigned in the connector plug, as the ribbon will only say plus or minus.

[danskiii]

im still in trouble with this.. should be easy but seems like im back to wondering wtf again.. do you have a pic showing what goes where? wiered the same as the diagram in the haynes manual now, but must be something wrong...

[dworthy]

Okay, lets start from the top. Did you replace the whole instrument clusters or just the tachometer?

[danskiii]

Sounds like a good idea! I just replaced the clock for the tacho, so not the whole instrument cluster.

[dworthy]

I don't think the ribbon for the clock cluster will have the extra line for the tach to work properly. So pull it back out, and look at the connectors. It has been a very long time since I last messed with a E-21 cluster, so bear with me. Can you take a photo of the plug on the tach and into the cluster?

[danskiii]

ill have to wait for tomorrow to take a picture from inside the car, but here is one from the gauge and from the haynes manual.
https://drive.google.com/file/d/0B_6...ew?usp=sharing
https://drive.google.com/file/d/0B_6...ew?usp=sharing

[dworthy]

Everything looks correct, so I would say pull the cluster and lets look at the back. Also does the cable have all 3 pins for the tach? Did you confirm that you were getting signal from the black wire too?

[danskiii]

Okay, Ive been outside now refitting the tachometer and took some pictures of the diffrent wires.
black wire: https://drive.google.com/file/d/0B_6...ew?usp=sharing
ground (fitted bigger contact): https://drive.google.com/file/d/0B_6...ew?usp=sharing
red wire is power (connected with green/white): https://drive.google.com/file/d/0B_6...ew?usp=sharing
video of startup: https://www.youtube.com/watch?v=sJSg34ONGYI
should i just try to switch around power and ground?

[dworthy]

Yeah, that tach isn't getting the proper signal.

Is there any numbers associated with the connectors on the back of the tach? Just a hunch, I would say that #15 is left, #1 is center and #31 is right.

Which plugs are you connecting and where?

[danskiii]

in the pic here i have wrote in color whats stamped on the tacho in red, and how the wiring is connected (as the haynes manual says) in green. hope you can read it.
what do you think is wrong? the two conflict with each other and confuse me..
https://drive.google.com/file/d/0B_6...ew?usp=sharing

[dworthy]

Yup, so try this:

Left is Brown
Center is Black
Right is Green/White

That would be my hunch, as I would go with what's written on the tach before you believe a hanes manual.

[danskiii]

I started with trying that, but then it doesnt respond at all. It just goes straight to max rpm on the dial and stays there.

[dworthy]

Okay, Next will be to check the wiring to ensure you are getting what it states: Green/white 12V +; Brown Ground; Black signal, which should go from I think 5V to 12V, again I am not exactly sure on what the signal wire will produce.