1993 Explorer Heater blowing warm air and temp gauge is all over.

[Manimal77]

I am new to this forum, but have been using it for reference for some time. I have read all of the posts I could find regarding this problem and have wasted alot of time trying to fix this problem with no positive resolution.

Ok, the problem started when the temperature here in Wisconsin began to drop and I needed to turn on the heater in my Explorer. Heater would only blow slightly warm air, but at this time the temp gauge remained the same and didn't move around. I changed the thermostat with another from Advance Auto and burped the system....alot. After this the temp gauge would go back and forth between the N and the L on the gauge. Still only warm air from the heater. Then I changed the radiator cap. turns out the one that was on there was a 10lb and needed to be 13lb. Still no change. Today I installed another new thermostat that I bought at the Ford dealership and is identical to the original. Still only warm air, but now the gauge fluctuates in different cycles. It heats up to the L then drops to the N then heats up to M then drops to the cold line and then starts over. Both hoses to the heater core are warm and I cannot find any leak. Once when I opened the hood I did notice the upper radiator hose was sucked in on itself. I have not seen it do this since then.

I anyone has any idea what this problem any help would be appreciated.

 

[Manimal77]

Turned out this Explorer had multiple problems. I ended up replacing the computer after replacing the coil pack, plugs, wires, fuel pressure regulator, MAF sensor, cleaning out the throttle body, and multiple other sensors. It ran great until the intake manifold gasket blew about a month later. I have since replaced that also. If this vehicle doesnt give me 100,000 more miles, I'm gonna blow it up. Seriously.