heater problems on 1995 Ford Taurus

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I have put in 2 thermostats and had the cooling system flushed and I have either no heat or poor heat. The temp gauge is also going crazy. It sometimes goes all the way over to hot and then goes right back down into the normal area.
I noticed a sending unit on the manifold with a heater hose coming off it. Is this the temp gauge sending unit and would it cause the car to do this? Thanks for the help.
(3) Answers
Often the water pump fins will corrode on the ford 3.0lL engine causing poor or no heat. If this isn't the case, look along the fire wall at the back of the engine bay. You will see a hose that bypasses the heater core, block this hose off with a valve, (obtained at any parts retailer) and see if that corrects the problem.
You might want to change your heater core. It could leaK. how you can tell is by noticing anti-freeze on the window.
Check and replace temperature sensor.