The temp gauge on my 52 M3 reads hot all the time. I've tracked the problem down to the left sender, by grounding out all the varoius components and wires from the gauge back.
My question; is there a difference between senders? Do I need to specificly look for a 6 volt sender? Where would be a good source for one (preferably in Canada)? My usually reliable NAPA outlet does not list them.

 

Hi

There is a difference between the left and right temp sendors. The right sendor is the one that actually measures the engine cooling temp. It is a variable resistor whose resistance value varies proportionatly with temperature. I don't know if the resistance increases or decreases with an increase in temperature or what the resistance should be at any given temperature. The one on the left is just a temperature switch that is normally closed and opens when it goes above the set temperature. The wire on the right resistance changing sendor is routed threw the left temperature switch. When the left switch is closed when it is below its trip point, the signal from the right sender is routed through the closed left switch to the gauge on your dash. When the left switch goes above its trip point, the switch opens and your gauge will move to the 3 oclock position, the same position it would move to if the wire from the right sender broke. You can check the left sender with an ohm meter. Remove the wires on the sender and connect the ohm meter across it. It should show closed contacts (between 0 and 5 ohms) unless the engine is overheated. I don't have a schematic in front of me at the moment so this is all from memory. I may have left and right mixed up but I think I am right. If I am wrong, I'm sure someone will be along to correct me.

Is your truck still 6 volt. Here is an article on how to convert to 12 volt if you are interested. https://www.ford-trucks.com/article/...on_Guide_.html

I hope this helps you. If you have any more questions, please ask.

Rick

 

Thanks Rick
I think I will stay with the 6 volt system for now, as it is giving me no problems yet.

I believe my problem lies with the left sensor (drivers side, single wire) as when I ground out the wire from it the gauge returns to cold.

Any idea of where I could source one of these?

john

 

they pop up on e-bay pretty regularly. Good Luck!

 

Hi John
Sounds like you got the problem solved. Grounding the single post sender and seeing the gauge go to cold also tells me the contacts in the double post switch(on the oposite head)are closed. I noticed your single post sender is on the left side. I think it is on the right side on most trucks but I don't think it matters which one is on which side. Just ask for the single post 6v sender.
Mid Fifty has them on Pg. 121 of their catalog for $50.00. I haven't started buying parts for my flatheat so I am not very familiar with flathead parts vendors yet. I'm sure you could find more on the internet or someone else could come on here to add more.

Rick