Having a problem with no heat or intermittent heat.

Tried all modes and fan settings. With temperature in warm position, either get no heat at all or sometimes heat for a short period, anywhere from several seconds to several minutes. Then air goes gool. If I shutoff completely, wait a few minutes, turn back on, I'll get heat for a while. The time varies.

Engine temperature is in normal range for a warmed up engine.

Hey montana.........First off Welcome to L.O.S.T. If you have'nt already,you want to make sure the radiator is full.Next step would be a new thermostat and a cooling system flush.These two things are good maintanence,so if they still don't get you good heat,your final resort would be to disconnect both hoses to heater core and forward and reverse flush it.In a rare instance you may have a heater core so plugged up that it can't be flushed,but again that is rare.Someone else may chime in with better advice,as everyone on here is usually very helpful.Again ,Welcome Aboard!....

Ron

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Ron
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I think Ron has it right. I didn't see what year you have but thermostats are inexpensive plus a back flush will get an amazing amount of crud out you would never beleive it even ran . Check out a back flush which runs the fkush in the reverse direction. Sounds to me like a heater core blockage. But I'm just an old shade tree mechanic listen to Ron he does this for a living so he has a vast knowledge base, Good Luck

Thanks for the replies. It's about time for a coolant change, so I'll do a flush.

Some additional info. I have determined that heat/no heat is related to engine RPM. I get no heat at idle, do get heat at cruising RPM. When I come to a stop and engine is back at idle, temperature cools after several seconds.

I was thinking about the blend doors on the HVAC that I believe are vacumn controlled. Wondering if a vacumn leak, could be the cause....

The blend door is actually electronically controlled. The only thing vacuum operated is the mode door (the official name escapes me right now).

From what you describe, you still could have a blockage or possibly the water pump going bad, although if it was going bad, I'd expect you would have problems overheating at idle. I'm guessing you are low on water or have something blocked. Let us know what you find, good luck!

Found coolant was low. I thought it was full when I first checked by looking at side of reservoir. When a climbed over and looked down thru opening, I could see it was quite low. Added about 1 quart of coolant. Fixed the problem. Thanks again for the help.