i have a 90 EB and my stupid heater is blowing cold air on and off. i got into it this morning and everytime my temp gauge goes to the hot side, i get cold air. i checked the water resevior and it was mt, so i filled it again, but it didnt help with the temp gauge or the heater..please help me cause its very very cold right now and i dont want to freeze anymore..
thnx

 

It sounds like you possibly have at least 3 problems, a thermostat stuck open, a coolant loss somewhere, and the gauge/sending unit sounds suspicious.

Do I understand correctly that the gauge goes into the over heating zone on the guage also?

Something else that may be worth checking is the valve that opens and closes the flow of coolant to your heater core.

 

just the gauge goes into the red zone..my engine isnt actually overheating.

 

I know you put water in the resevoir but have you pulled the actual radiator cap and sean if it is empty. It sounds like your running way, way, low on coolant.

 

A fix for the cold weather thing is move to Texas. It has been in the mid 80's here this last week and hot and humid.

 

If all you are getting is cold air and the gauge is showing over heating, sounds to me like you have a clogged heater core or part of your cooling system is clogged. (Yea i know the HC is part of cooling).....Try back flushing your system and see what comes out. If that doesnt work then I would check all your heater hoses for nasty clogs and if nothing there...then I would replace your heater core.
Good luck!

 

well..im actually from texas..unfortunatly i am up in washington for school..and its a bit to chilly to be without heat..well, im gonna go and start tinkerin ..

 

Honestly, it sounds to me like your coolant level has dropped low enough that you have a large air gap (bubble) in the system. If the coolant level drops too far, the system will not draw coolant into the radiator from the overflow resevoir so your problem won't be solved by merely refilling the resevoir. Instead, start the truck cold with the radiator cap off. Keep an eye on the coolant level in the radiator itself. As the temp begins to climb the level should drop significantly once. Thats your thermostat opening. Once the thermostat has opened, top off the radiator and replace the cap. Then fill the overflow resevior to the "full hot" mark. No need to shut the truck off yet, take it for a drive and see if your heat works any better.