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Tachometer help

Wayne67vert

Donation Time
I have a Series 5 Alpine. My tach has been running 2x the motor speed. I purchased another tach that turned out to be a positive earth. I did the switch of the resistor and ground wire.
I have installed it and now can't get it to work. I have the white wire spade connector hooked up. I have the white wire with the white plastic piece connected. I have the 3 ground wires connected. I'm obviously missing something.
I even tried my old tach and it doesn't work now either.
Thanks for any advice you can offer.

I just remembered I don't have the white plastic connector making the wire going around the post. Could this be my issue?
 

junkman

Gold Level Sponsor
It's an induction tach, so you have to have the loop of white wire that goes to the ignition switch. See the oval hole in the plastic piece? That's where you loop the white wire. There are most likely pictures in here somewhere if you have time to search.
 

bernd_st

Bronze Level Sponsor
Did you put the steel bracket over that plastic piece? The induction circuit doesn't work without one...
 

Wayne67vert

Donation Time
Yes I did put the steel bracket over the plastic piece. What I didn't do was make sure the wire was looped around the steel bracket. I'll be back at it in a short bit and let you know my progress.
 

Wayne67vert

Donation Time
I'm stumped! I got the wire wrapped around the steel bracket and still nothing. I even changed the direction the wire is wrapped. Is there another wire that I'm not seeing that needs connected?
 

bernd_st

Bronze Level Sponsor
Of course you need good grounding on the instrument (black cable) screwed under the holding bracket nut as well as +12V (green cable) on the rear spade connector. You may check with a bulb whether 12V is really there...
 
Last edited:

hartmandm

Moderator
Diamond Level Sponsor
Was a claim made that the tachometer you purchased had its internal components updated and then calibrated? If not, it most likely will not be accurate and will need some work.

I'd suggest you see if Tom H can fix and calibrate your original tachometer.

Mike
 

Tom H

Platinum Level Sponsor
Easiest way to verify the ground is to see if the tach's lamp lights up when the dash lights are on.

Be sure that when you loop the wire thru the steel clip that the tips of that C-Clip are making contact with the tips protruding out from inside.

Since your old tach does not work now either, I suspect you did something with the wires while the tach was out. Ground? See above. When you removed the tach did you cut the wire that loops thru the C- clip? If so did you run a separate wire to the coil so the car would run even with the tach removed? If so, you now have two paths from Ignition switch to the coil so at least half the coil current does not loop thru the tach and that's your problem.

Note that, unless someone calibrated that Positive earth tach, it will be very unlikely to be any more accurate than your original tach. (see Mike's note above).

See my article here to see what I know about these tachs. (Thanks Mike)

http://sunbeamalpine.org/wp-content/uploads/2017/10/alpine_tach_repair_rev5.pdf

See page 11 for details on the wire loop

Send me an e-mail : tahayden42@live.com and I'll give you my phone number if you need more clarification.

Tom
 

Tim R

Silver Level Sponsor
You probably know this but the wire has to be looped the correct way. If you loop it in the opposite direction it doesn't work. Personally I have the tachos fitted with a Spyder set up. It is very accurate and less hassle than the original but looks identical.
Tim R
 

gary1725

Donation Time
Hi Tim, what did you mean "a Spyder" set up - do you do this yourself? or ship it out? Years ago I swapped the face and needle over for a late model MGB unit to eliminate the induction loop but 10 years or so later that Tach is now playing up.
 

Wayne67vert

Donation Time
I reinstalled my original tach and now it works like it did before I removed it. I don't want to spend money to have this one rebuilt and calibrated after paying for a replacement that doesn't work.'
If I decide I need an accurate tach, I will get one that runs off the distributor signal.
Thanks for your suggestions.
Wayne
 

Tim R

Silver Level Sponsor
Gary,

Spyder are a company that make a different type of internal system for Tachos. They work in a different way.You send the rev counter to them and it comes back converted. It wires up in a different ay but is very accurate and doesn't seem to cause any trouble. It looks identical in the dashboard.

tim R
 
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