Wiring an old Stewart Warner green line tach.

[dan juhasz]

It worked when the car was disassembled couple years ago. There was no separate module to act as a driver. Is this a positive + feed tach? Hooking to the positive side of the coil. Then supply any ground to the negative side?
Thanks Dan

 

[pnora]

Tachs need to run off the negative side of the coil.

 

[RemCharger]

Not all tachs. That's more of a modern thing.

 

[pnora]

Not all tachs. That's more of a modern thing.

Most older ran of the coil negative.
Ones like pictured commonly ran off a driver module of some sort.
Msd usually have a driver port.
Most all automotive production tachs run off the pcm.

 

[pnora]

This one says it must be used with a sender/driver. Yours could be different but just about anything I have seen of that style needed a module/sender/driver to make it work.

 

[RJRENTON]

Tachs need to run off the negative side of the coil.

Why not just connect it like the printed instructions note....2nd pix in OPs note, as see what happens......just a thought.....
BOB RENTON

 

[dadsbee]

 

[bigorange426]

Brings back memories I had a SW Tach exactly like yours back in the day...

 

[RJRENTON]

View attachment 1819011

Not likely to happen......the tach will work ....or.....not. S&W would have designed a circuit to prevent damage to the unit if wired incorrectly..........just my opinion......btw a bottle of instrument panel smoke is similar to a bucket of prop wash......or a fart in a wind storm......???
BOB RENTON

 

[pnora]

Not likely to happen......the tach will work ....or.....not. S&W would have designed a circuit to prevent damage to the unit if wired incorrectly..........just my opinion......btw a bottle of instrument panel smoke is similar to a bucket of prop wash......or a fart in a wind storm......???
BOB RENTON

The one picture I posted says warranty void if used without sender. So there must be something to it that makes it fail. Liquid smoke applies here.

 

[RJRENTON]

The one picture I posted says warranty void if used without sender. So there must be something to it that makes it fail. Liquid smoke applies here.

Sorry....did not see the pix with that note. Some of the S&W sending units used MERCURY BATTERIES () like C or D size) mounted on the engine side on the firewall or fender hump, received the distributor (or Dizzie if you prefer) pulse, 12 volt from car, but used batteries....for the meter movement???....not sure what the internal batteries did.....
BOB RENTON

 

[pnora]

Sorry....did not see the pix with that note. Some of the S&W sending units used MERCURY BATTERIES () like C or D size) mounted on the engine side on the firewall or fender hump, received the distributor (or Dizzie if you prefer) pulse, 12 volt from car, but used batteries....for the meter movement???....not sure what the internal batteries did.....
BOB RENTON

I also thought some mags had a special device for an electronic tachometer. Pretty sure an old Arias Hemi I owned had one.

 

[dan juhasz]

View attachment 1819011

Laughing my *** off, that’s funny

 

[Vaanth]

It worked when the car was disassembled couple years ago. There was no separate module to act as a driver. Is this a positive + feed tach? Hooking to the positive side of the coil. Then supply any ground to the negative side?
Thanks Dan

View attachment 1818886

View attachment 1818887

The small gold assembly attached to the meter terminals is the sender for this Stewart Warner tachometer. The early 60s and earlier electric tachometers of this style used either a remote sender unit or the small meter attached sender unit. Sun and Autometer operated similarly. The sender units have their own internal power supply in the form of a cell, or two cells.

The remote and attached sender units have the following connections:
- Meter plus (+) which connects to meter plus on the tachometer
- Meter minus (-) which connects to the meter minus on the tachometer
- Distributor primary which connects to the distributor connection on the coil (- terminal); alternatively, an electronic ignition connection to the coil (- terminal) if compatible
- Ground connection which connects via engine or chassis ground and/or tachometer housing

The sender shown in the picture is the Stewart Warner V-type sender which attaches directly to the tachometer "METER" "+" and "-" terminals. The "GRD" terminal attaches to the tachometer housing stud/nut. The "DIST. PRI." connect to the coil "-" terminal (yellow wire in the picture). These meter connections are similar connections to a remote sender unit via wires. The white "+" and "-" markings on the tachometer denote the matching sender connections. "6 65" denotes the sixth month of 1965. The lamp connects to a 12 volt power source and is grounded through the tachometer housing.

The attached sender part number, cylinder count and other information is on the side facing the meter:

Mercury cells were long lived power sources in low drain applications. The cells have been banned for years. Remote senders may have larger replaceable cells. The meter attached sender cells are small and likely not intended to be serviceable. Mercury cell voltage is 1.35 volts. A modern equivalent voltage might be found with some zinc air cells adapted to fit or by rigging up a solid state power source. The internal cell in the pictured unit might still be viable, but could expire at any time.

Some catalog information from Stewart Warner:

Autometer made a similar sender:

 

[dan juhasz]

The small gold assembly attached to the meter terminal is the sender for this Stewart Warner tachometer. The eary 60s and earlier electric tachometers of this style used either a remote sender unit or the small meter attached sender unit. Sun and Autometer operated similarly. The sender units have their own internal power supply in the form of a cell, or two cells.

The remote and attached sender units have the following connections:
- Meter plus (+) which connects to meter plus on the tachometer
- Meter minus (-) which connects to the meter minus on the tachometer
- Distributor primary which connects to the distributor connection on the coil (- terminal); alternatively, an electronic ignition connection to the coil (- terminal) if compatible
- Ground connection which connects via engine or chassis ground and/or tachometer housing

The sender shown in the picture is the Stewart Warner V-type sender which attaches directly to the tachometer "METER" "+" and "-" terminals. The "GRD" terminal attaches to the tachometer housing stud/nut. The "DIST. PRI." connect to the coil "-" terminal (yellow wire in the picture). These meter connections are similar connections to a remote sender unit via wires. The white "+" and "-" markings on the tachometer denote the matching sender connections. "6 65" denotes the sixth month of 1965. The lamp connects to a 12 volt power source and is grounded through the tachometer housing.
View attachment 1819199

The attached sender part number, cylinder count and other information is on the side facing the meter:
View attachment 1819202
Mercury cells were long lived power sources in low drain applications. The cells have been banned for years. Remote senders may have larger replaceable cells. The meter attached sender cells are small and likely not intended to be serviceable. Mercury cell voltage is 1.35 volts. A modern equivalent voltage might be found with some zinc air cells adapted to fit or by rigging up a solid state power source. The internal cell in the pictured unit might still be viable, but could expire at any time.

Some catalog information from Stewart Warner:
View attachment 1819200

Autometer made a similar sender:
View attachment 1819204
View attachment 1819205

Great info thank you