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Gauges on an M20


Pierre
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I am not very good with electricals.

I would like to install an oil temp gauge.

Where do I install the sensor? Can I use a coolant temp sensor and gauge to measure oil temp or do I need an oil temp specific setup?

Regarding the tach, I read the fix by using a 5K OHM 10 turn potentiometer spliced between the 2 green wires under the face of the tack. Did anyone ever measure the actual resistance necessary to make the stock tack work with the 6 cyl signal?

One more thing. I would like to install two coolant temperature gauges, at least temporarily. The stock one and another one to calibrate the stock one. Can I take the reading for both gauges from the same sensor? Will it be accurate? Or does anyone know if the stock M20 sensor is correct for the stock 02 temp gauge?

TIA

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Oil temp on my M20 car has its sensor in the drain plug.

Coolant temp uses the factory M20 sensor into the factory 2002 gauge and will read right in the middle for 180ish degrees no problem. I also have an autometer gauge on a second sender in the thermostat which has a readout so I know right where it runs more accurately. Let me know how I can help!

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Oil temp on my M20 car has its sensor in the drain plug.

Coolant temp uses the factory M20 sensor into the factory 2002 gauge and will read right in the middle for 180ish degrees no problem. I also have an autometer gauge on a second sender in the thermostat which has a readout so I know right where it runs more accurately. Let me know how I can help!

Thanks for the reply Curtis.

Did you use an oil temp gauge or a coolant temp gauge? Do you know if there is a difference?

What did you do for a tach?

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I run two temp gauges, stock and a VDO unit mounted in the center column. I removed one of the extra "plugs" on the thermostat housing and added a VDO temp sender, then hooked this up directly to the VDO unit.

As for the tach, I bought a potentiometer from Radio Shack and a 6cyl tach from Harbor Freight. Soldered the potentiometer onto the back of the tach, then hooked up the Harbor Freight tach to the coil. Turned the engine on and adjusted the potentiometer on the stock tach to output the same reading that was on the 6cyl tach. Rev the engine a few times to make sure it is adjusted properly, then you can remove the Harbor Freight tach, put it back in the box and return it if you're so inclined. Leave the potentiometer hooked up to the stock tach and re-assemble the console - you now have a tach adjusted for 6 cylinders.

- Chris

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I run two temp gauges, stock and a VDO unit mounted in the center column. I removed one of the extra "plugs" on the thermostat housing and added a VDO temp sender, then hooked this up directly to the VDO unit.

As for the tach, I bought a potentiometer from Radio Shack and a 6cyl tach from Harbor Freight. Soldered the potentiometer onto the back of the tach, then hooked up the Harbor Freight tach to the coil. Turned the engine on and adjusted the potentiometer on the stock tach to output the same reading that was on the 6cyl tach. Rev the engine a few times to make sure it is adjusted properly, then you can remove the Harbor Freight tach, put it back in the box and return it if you're so inclined. Leave the potentiometer hooked up to the stock tach and re-assemble the console - you now have a tach adjusted for 6 cylinders.

- Chris

Thanks for the info Chris.

I did the potentiometer trick by attaching it to the two green wires inside the tach. It wasn't hard but I had to disassemble the whole unit to get to it. Did you say you hooked it to the back of the tach?

I have had a dwell meter/tach for 30 years when I had a Chevy and you could adjust the points WHILE THE CAR WAS RUNNING. I was able to calibrate my tach with it and it seems to work.

The T-stat housing on my M20 does not have any additional plugs. It only has the two that are already occupied. There is a spot I could drill and tap but it's probably easier to get one that has 3 ports.

I am going to try the electric speedo from North Hollywood speedometer. We'll see how it works out.

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