my heater won't work unless i'm on the highway (60MPH), is this the heater core going bad or the thermostat sticking?

 

Check ur coolant level, and make sure the heater valve is fully opening.

 

coolant has been fine, where's the heater valve? under passenger dash?

 

next to the header on the pass side.

 

i'll check it out... thank you

 

Hi,

So, have you checked it? Is your heater ok now?

 

There is a motorized valve on the pass side next to the hose that loops back into itself at the firewall. Have someone inside the car turn the temp control from cold to hot and ensure that the valve moves all the way. I had a problem with no heat and thought I had a coolant problem...turns out the heat shield from my turbo setup was blocking the valve from opening all the way

 

Caveat...my heat didn't work at all. Didn't matter how fast I was going. Your issue may be different.

 

By not working, do you mean that the fan isn't blowing? Your description sounds like at 60mph, the incoming air is moving fast enough to move the heat (assuming recirculation is OFF).

 

Check fuses.