I have a '69 with a non-working temp. gauge. It stays in the middle. I have the 1969 Ford Car Shop Manual and tried the following: new sending unit, checked the inst. voltage reg. at the lead with a meter and got the pulsing voltage, put a 10 ohm. resistor at the lead and the gauge went full high, used a 100 ohm. resistor at the lead and the gauge stayed in the middle(should go full low). The conclusion I draw is that the gauge is bad. Has anyone had this problem and do the gauges go bad? The fuel and oil press. work fine.
Thanks
Rick

 

It is vary possible the gauge is bad, they can go bad. Put a mech gauge in there for an accurate reading.

 

Just as an extra check, try running a temp new wire from the temp sensor to the back of the gage, bypassing the old wire. See if that makes any difference.

 

Thanks for the info. I plan on eventually changing the whole dash out but for now just wants things to work. I'll try the wire bypass.
Rick

 

I too have a 69 with a similar problem. My temp gauge goes too far towards "H", when Im pretty sure the engine is not running that hot. What engine do you have? Mine is a 351w, and I replaced the tsu (temperature sending unit) with a Mustangs plus piece. The new one is longer and looks different, which could be the problem. And I think that their website info is incorrect, but it says I ordered the right one (maybe the packagers put the wrong one in the box?).

 

Yes, gauges can go bad. Another test-pull the wire all the way off of the sender and the gauge should go to it's lowest point. If it stays in the middle, it's the gauge.

 

+1
that's probably the quickest way to check the gauge as you confirmed the other direction already