My tach quit working after a new engine install a few months ago

Is there a way I can wire the tach up by bypassing the harness from the distributor to the tach under the dash
If so what color wire do I need to tap into and which pin on the back of the cluster
is the sensor pin for the tach?

I mainly want to see if the tach can be hardwired by bypassing the harness to get it to work

1980 Rx-7 12-A turbo lots of mods, original cluster and wiring harness
thnx

 

Wouldn't it make more sense to just fix the issue?

See if you have spark on the trailing (top) spark plugs. You probably lost the trailing ignitor, which feeds the signal to the tach as well...

 

Although if it was a stock 1980, then he would have to check out leading because that is where they got the tach signal from (since trailing was part-time). However, since this is a new engine, 12A turbo at that, who knows how it is setup.

We need to know what ignition setup you are running. Also check for spark on all 4 wires. It could be that you lost an ignitor, coil, or some wiring became disconnected. If you have spark on all plugs, then the ignitors/coils/etc. are good. Then it can be wiring (not very likely) or the tach itself.

Also since it is a 1980, the tach is shared with the voltmeter. When you say the tach is not working, is it reading 0 or is it reading volts? I ask because there is a relay that switches it from volts to tach (could be bad). Is the battery charging? Are any of the warning lights on? A bad alt could also keep it from switching from volts to tach.

So start by checking these things out and give us as much detail as possible. It is much better than trying to bypass the harness only to find that it didn't cure the problem.

Kent

 

Kent,
Its basically a stock ignition setup with 2 big yellow coils
the temp guage does not work anymore either.
the alt light is coming on but it charges the battery fine
the temp guage just slowly goes up and engine is running cool so is the oil light
the oil light i know why its on, both sensors are unplugged ...damaged in the install process just dont have the cash to get new sensors...might try to find from a guy in oklhoma that ive gotten parts from in the past.
im pretty sure the watertemp sensor is good i think i checked it with an ohm meter
a few months back to make sure.
in other words the only thing that should be on is the oil light

 

okay..so just to be clear, is the tach reading volts or is it reading nothing? If reading nothing, does the voltmeter work before the car starts? I'm thinking it might be that relay or the wiring from the alt to the relay.

I might have those sensors for you. I have an oil pan from my old '80. Still has the sensors. I'll check them out for you. I'd be happy to give them for the cost of shipping if they are good. You could have the whole pan if you wanted.

Kent

 

the tach its reading nothing but when it started acting up
it would read like 8k when i cranked it then when id rev it up it would peak out then die to 0

ok this car is someone elses headache i bought
he did say it had voltage anomalies, stupid me. lol i like a challenge sometimes

as far as the oil sensors ill gladly pick them up cod or send you a money order for them i dont think i need an oil pan i can pm you with address if you like

let me look at the 7 book and see how many wire are supposed to go to the alt and find out where the relay is

thnx a million for steering me in the right direction on this ill have some fun tommorow checking all this out

 

Check the main power wire at the starter while you're at it...

 

Ok i hooked up the altenator plug and all the lights temp oil ect. dont work now at all
there is no voltmeter in this car previous owner might have removed it or it might not have come with it i just dont know
good googleygoo this is getting interesting i think i might un hook it on sat to see if they come back on