Tick tock tach showing double

[Sir Sner]

So I have a tick tock tach out of a '69 Coronet that reads double what it's supposed to. I cracked it open and can't find anything obviously wrong. Any help would be appreciated.

 

[hunt2elk]

It will read wonky if it is an original tach and you converted the car to electronic ignition.

 

[R413]

What ignition system, few run points anymore.

 

[Billccm]

I used the circuit board from rt-eng.com and it's accurate with MSD ignition.

 

[Sir Sner]

What ignition system, few run points anymore.

Should have added that, still runs points. Although I think it should be a dual point distributor since its a 440 hp but it only has a single point distributor in it now.

 

[MWbirdLOVER70]

Should have added that, still runs points. Although I think it should be a dual point distributor since its a 440 hp but it only has a single point distributor in it now.

Single or double it shouldn’t matter

 

[Sam69sat]

I see what looks to be a potentiometer on the board. That cause me to search for "tachometer adjust potentiometer". This is the first article that came up for me but looks like there are a bunch more. I don't know anything about these though so tread carefully.

https://www.camaros.net/threads/1967-tach-adjustment.76656/

 

[Runner 68]

Reads double on what, time or RPM?

 

[Demonic]

Get the RTE board.

 

[steve817]

Make absolute sure that your distributor is not wired backwards.
Taken directly from RTE website: "It turns out that if you wire in a mopar distributor backwards, it will double fire at low RPM, but it will properly single fire at higher RPM. You need to swap the two wires coming from the distributor to the electronic ignition box."

 

[velocityss1985]

Is that the factory board? I thought they were on cardboard.

 

[Billccm]

Make absolute sure that your distributor is not wired backwards.
Taken directly from RTE website: "It turns out that if you wire in a mopar distributor backwards, it will double fire at low RPM, but it will properly single fire at higher RPM. You need to swap the two wires coming from the distributor to the electronic ignition box."

I was going to bring that up, but he said he's running points. Perhaps he should rev it up a bit and see if the tech results fall?

 

[Billccm]

Is that the factory board? I thought they were on cardboard.

It's a phenolic material for the circuit board.

 

[RemCharger]

Make absolute sure that your distributor is not wired backwards.
Taken directly from RTE website: "It turns out that if you wire in a mopar distributor backwards, it will double fire at low RPM, but it will properly single fire at higher RPM. You need to swap the two wires coming from the distributor to the electronic ignition box."

Who figured out how to turn a chrysler ign into an MSD ? MacGyver?

 

[RJRENTON]

I see what looks to be a potentiometer on the board. That cause me to search for "tachometer adjust potentiometer". This is the first article that came up for me but looks like there are a bunch more. I don't know anything about these though so tread carefully.

http://[URL][URL]https://www.camaros.net/threads/1967-tach-adjustment.76656/

[/URL][/URL]

It appears as if most (all) of the origional parts have been up graded, including the calibration potentiometer. I believe the tachis is RMS reading volt meter and the circuitry measures the pulses the coil receives translated into RPM. Your best bet is to replace the entire board assembly with the RTE board....it's an exact fit....follow the instructions.....end of problem......just my opinion.....
BOB RENTON

 

[RJRENTON]

Should have added that, still runs points. Although I think it should be a dual point distributor since its a 440 hp but it only has a single point distributor in it now.

I believe that the 440 six barrel 4 speed cars and the HEMI used the Prestolite Dual point distributor the rest gor single point Mopar distributor......
BOB RENTON

 

[Billccm]

It appears as if most (all) of the origional parts have been up graded, including the calibration potentiometer. I believe the tachis is RMS reading volt meter and the circuitry measures the pulses the coil receives translated into RPM. Your best bet is to replace the entire board assembly with the RTE board....it's an exact fit....follow the instructions.....end of problem......just my opinion.....
BOB RENTON

The circuit is a two transistor integrator with some hysteresis. I would bet that replacement of all capacitors would restore operation, but the RTE upgrade has a two point built in calibrator, and works with points, or even MSD, plus other electronic ignition.