2000 ZX2, temp gauge pegged full to the hot side and stays there even when engine is cold or off. Put new sending unit in and have no change. Is there a fuse in this line or is this a bad gauge , a short, or other problem.
replaced the sending unit located on the thermostat housing. parts store showed a sending unit that clipped in or one that had a larger thread size than the one I replaced. Do these cars have more than 1 temp sending unit?

 

I think there are two sending units. One of them is to tell the cooling fans when to turn off/on and the other is the sending unit for the gauge. I have a Contour with the Z-Tech 4 cylinder which is the same engine as the ZX-2 has and I had a problem with the gauge on it being incorrect several years ago. I replaced the sending unit on the thermostat housing and it took care of the problem. You may have a bad ground somewhere causing the gauge to read wrong.

 

I finally got it right while trying to fix a temp gauge that was pegged on hot. I first replaced the gauge itself with no success. I then replaced the sending unit located above the thermostat housing, and again no success. I thought I would try one more time and I replaced the sending unit located under the thermostat housing and bingo, gauge works like a charm. I found out that the sending unit on top works the fans and the sending unit underneath (which is very hard to see) controls the temp gauge, thus problem solved $100.00 after all said & done.

 

Technically speaking no.
There is one temperature control sensor and one temperature control sender.
The sensor tells the electric fans when to kick in and shut down while the sender operates the gauge.

It sounds like you replaced the sensor for the fans. Not a big deal the price of the sender is only a few bucks.