Tachometer not working

If power to the coil is coming from somewhere other than the pink wire from the tach, that’s the reason the tach is not working. Edit - …and the pink wire from the tach should go to the 3 terminal connector on the firewall along with the oil and temp sensor wires. The engine harness referenced above plugs into that connector and routes wires to oil and temp sensors and coil.

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Where else could it be coming from. The 3 terminal connector doesn’t have a pink wire. Has red with green stripe, white with red stripe and red with white stripe.

That’s incorrect. The + wire to the coil is the wire that comes from the tachometer. It has the white elbow shaped connector. There is not a separate wire from the tachometer,

That’s incorrect. The pink wire is under the dash. It connects to one of the tachometer wires and runs to the firewall to the rear side of the engine feed harness plug.


Disregard my prior post. Red/green stripe is the correct engine harness wire that goes to the BAT terminal of coil. It plugs into the pink wire from tach at the firewall plug.



Here are some pics. From what I can tell I believe the white and red wire that’s burnt is the tach. That was hooked to the dist side of the coil. There’s a blue with black stripe that was hooked to the battery side. There’s a red wire that looks to be for a pertronix. There’s a black wire that also hooks to the dist side of the coil. The rest of the mess I’ll resolve with the 3 prong harness I have.

Yeah, I would just throw that taped up harness away and use your new one. Your current harness apparently gets power for the coil from somewhere else which is wrong. White/red stripe goes to oil sensor, red/white stripe goes to temp sensor, and red/green stripe goes to BAT terminal of coil. DIST terminal of coil goes through black wire to distributor points. As long as the 3 factory wires are still connected to the other side of the three terminal connector at firewall, you should be up and running with tach.

Thing is the tach worked fine before with the way the current harness is setup. I’m concerned if I hook up the new harness something will go wrong since that’s not how it appears to be setup. What about the white/red wire, black wire that we’re on the dist side of the coil and the blue/black wire on the bat side?

What’s the best way to get the oil pressure wire off and the new one back on? I don’t see a good way to access it without taking some of the accessories off. Here are some more pics of the harnesses. The plug at the firewall does have 3 wires still. The harness with the blue/black wire runs inside the car as does the pertronix wire. The white/red wire appears also to connect to this harness inside the engine bay as only the blue/black and red wire run inside. There’s also a very thin blue wire wrapped around these two at the firewall but I’m not sure where it goes before or after this.




Obviously it’s not hooked up the way it was with the old engine. It’s possible to have the tach working with a Pertonix but currently you have what appears to be an unknown rats nest of mis - attached wires. We can tell you how to hook it up properly with points, or how to modify it to work with the Pertronix. So far you don’t know what you have and neither do we despite lots of good intentions.


Sorry, I was assuming you were going back to factory ignition with points. Can’t help you on Pertronix.

How do I modify it for pertronix? Is the blue/black wire that goes to the bat post not factory? I think we’ve established that the white/red wire that went to the dist side is not factory and has been spliced into I believe the red pertronix wire. The original red/green wire to the coil was apparently bypassed in this setup. The other wires for the oil and temp are as factory.

How is the best way to access the plug for the oil pressure sending unit? Do I have to take off the power steering pump and/or a/c or is there an alternative way? I can probably get it off with some long pliers but not sure I can plug the new one back on because I can’t reach it with my hands from the top or the bottom

Bill Basore has posted the Pertronix schematic many times. Here it is - the majority is existing and you need to get rid of all the non - stock wiring to make it work right. The Pertronix unit needs a single wire from the + side of the ignition - the same wire that connects to one side of the tachometer under the dash. You can easily make a connector so that none of the factory wiring is cut or modified in any way. Be absolutely certain that the stock resistance wire is in place and connected, as well as using only a stock coil as I see in your photos.

The easy way to connect the oil pressure sender is by removing the oil filter so you can easily touch it / plug it in from underneath.

What color is the stock resistance wire? I know pink has been mentioned but that’s under the dash right? What color would it be under the hood? Is the blue with black stripe wire that went to the battery side of the coil factory? Red pertronix wire accounted for. White with red stripe spliced into that isn’t factory that was attached to the distributor side of the coil. There’s also a black wire attached to the distributor side of the coil. Is this factory?

The blue w/black wire is not factory - what is it connected to?

The black wire from the distributer to the neg. side of coil is from pertronix. If you had points, that wire would be routed the same. Temp gauge is red w/ white tracer. Oil pressure is white w/red. The resistance wire circuit is red w/green tracer under the hood and part of same harness as the gauges.

What is your red pertronix wire connected to?

It’s pink under the dash. It goes from one side of the tach to the bulkhead connector for the engine gauge feed on the firewall.

There is no resistance wire under the hood. The wire in the engine gauge feed leads from the dash to the + side of the coil. It’s a plain piece of wire with the elbow connector at the coil.

That’s a pretty simple setup! As Royce pointed out, everything is factory wiring except for the switched power to the module. We have already discussed all of the colors and connections of the factory wiring. So you can just use your new engine harness to get power from pink tach wire at the three terminal firewall connector to BAT terminal of coil. Black wire on factory ignition goes from DIST terminal of coil to points inside distributor. Yours will go to the module instead of the points. Then you just need to tap into a source of switched 12V for the red wire to module.

Most likely what happened is that at some point a previous owner got confused about how to wire the Pertronix. No reason to do that. The Pertronix needs a source of power to operate. That means you need to run a single new wire from the back side of the key switch up to the red wire on the Pertronix. One wire, that’s it. Everything else hooks up exactly the way it did from the factory.

The easy way to run the new wire is to take short piece of 3/16" inside diameter brass tube and sharpen one end just enough so it is not totally blunt. Then slip to tube over a small Phillips screw driver or pick. Then pick a rubber grommet that goes through the fire wall. With the tube still in place on your pick, poke it through the rubber grommet adjacent to the factory wires. You need to be close enough to go through the opening in the steel. You are bigger and stronger than the grommet. Push the pick through until the brass tube goes through to the inside of the vehicle, with a short section still visible in the engine bay. Remove the pick and the brass tube will stay in place. Slide your new wire through the brass tube. Put enough through the tube so that you can find it under the dash. Tie it to something under the dash temporarily. Back under the hood pull the brass tube out of the grommet leaving the wire in place. Slide the tube off the end of the wire.

These little picks work great and cost all of $1.79

Use a butt connector to attach your new wire to the red wire connected to the Pertronix. Find the wire going from the key switch to the tach. It is typically pink with a green stripe but verify this for your year of production. Use a scotch lock to make the connection.

You are done.

P002. https://www.rccinnovations.com/index.php?show=menu-relays#ignition

I need to get this thing sorted out and at least get everything working that was working before. After looking under the dash, I think I’m in over my head here and need help to sort through this mess. Looking at the under dash and engine wiring, looks like way more than one person didn’t know what they were doing. I’m usually good with sorting things out and perhaps I can do this too with your help. Here are some pics. Please try to help if you can.







Household wire nuts are never a good sign. If this was my car I would most likely be taking the entire dash out to remove the complete underdash wiring harness. That way it can be closely and properly inspected. If it can be repaired and returned to stock that would be great. If need be it could be sent to someone like Midlife to work his magic on it. If it is too butchered up then it would be time to find a replacement harness.

Randy Goodling
CCOA #95