Temperature gauge does not work on my 1970 340 Duster ?

Mike69cuda said
I have had trouble with aftermarket sensors a lot. I have a trans am that I wound up buying the sensors from a GM dealer because I couldn’t get multiple sensors to work right. The way the cooling fans work is pretty marginal, so the sensors have to be pretty accurate. Works fine with the OEM sensors.

My temp gauge isn’t working & I built a simulator box and found my wiring and gauge were ok. My temp sender reads about 6500 ohms. I could have swore I checked it before I installed it. I have a post on it in the electrical section.

I’ll send it to you if you want, just pm me your address. It fits in a small flat rate box.

View attachment 1715282247

Wow, thanks for the super offer, not sure if is necessary though.
Please heck my logic on this;
The guy who I bought my voltage limiter from sent a resistor along with it so could verify my gauge was working. I'm not sure the impedance of the resistor, but it was supposed to read "F" (full) when used in placement of the sending unit, as oppose to pegged out when I did a direct ground of the lead wire. It did just that.
Everything I could find online only shows there is only one sending unit for that year, so i have the right part number at least. bought both from classic industries and i was marked as Genuine Chrysler part. When I check the ohms while it is heating up, it is moving: wether it is accurate nobody guess. When I remove the sending unit and dropped it into a coffe cup of boiling water, it registered about midway so I assume it is working, accurate, who knows. it cools down a bit from the kitchen to the shop. My only conclusion, be it logical or 'shade tree', is that there is something wrong with the installation. Dedicated ground was added to eliminate that discussion. I have seen signs of a slight intake manifold leak (bubbles at the top) I can only think that I am getting exhaust pushed into the cooling system somehow. My thinking would be that if that was the case I'd have a long list of the problems that would dwarf the temp gauge not working but I'm grasping at long shots on this one. I'm planning on pulling the engine when i paint and rework the seals on the engine especially the intake manifold so I'm hoping I find something that looks out of the ordinary.