I have replaced the thermostat in my 90 Ford Ranger several times. But, just to make certain, the exposed spring is suppose to face toward the engine, correct ? With the little loose rivit looking thing pointing straight up ? Still unable to get the heat going in this truck. With the truck running for 30 or 40 minutes one of the hoses going to the heater core is fairly warm, but not hot. And the other hose is cold. I have looked for mechanical controls, and cant find them, nor any vacuum lines. They may be there, but I dont see any. Want to try the thermostat one more time. Just want to make sure I put it in right. Any help ?

 

It is pretty clear that you have a clogged heater core. At the least attempt to flush it. Replacing it will surely correct the no heat issue.
Hope this is helpful to ya,
Billy

 

I guess you were right Billy. I removed the heater core and had a tough time getting it flushed out. Is there any way I can prevent this from happening again. Getting that core in and out is a booger bear. By the way, the heater is working great now.

 

Flush the entire cooling system more frequently and don't use any sealers.