It does it in my car too, i know it the wrong forum but when i posted in the other on i didn't get a clear answer. But in mine when the engine goes up 3k rpms the temp goes all the way to C and when the engine drops below 3k rpms it goes to normal. Is it a bad thermo or bad gauge?

 

i am having a weird prob with my hf too, the temp gauge says the motor is at operating temp. but i get no heat and the motor and radiator and hoses are all cool to the touch, i have tried bleeding the system and replacing the thermostat, but i still get no heat. i dont know what to do. and it really sucks because this is my daily driver that i deliver pizza in and i live in ohio where it is not very warm this time of year. plus no heat gives me no defrost so that sucks too.

 

Dod,
Are the heater core hoses cold too? Perhaps the diverter valve is sticking closed. This valve is what opens the flow of coolant to the heater core, it's usually cable actuated and should be situated near the firewall. I've seen cases where you will move the control inside the car, but the valve has rusted so the cable just moves. Try moving it by hand from the engine bay. Maybe shoot some PBBlaster on it if it doesn't move.
As far as your radiator hoses...hmm, both shouldn't be cool.
What thermostat did you use? The NAPA one I tried for the wife's old Integra was a complete POS. Make sure you get the Honda part...it's only a few dollars more.
I'd get this fixed asap as I'd consider it a safety problem to have no defrost in this weather...
Bogatyr

 

i get heat so blah

 

What does that mean? He was talking to Dod. We know you have heat.

 

i got it fixed, the thermostat got the everyhting to running temp, all hoses are warming up now. as for the heat the duct under the dash board which directs the air fro either the heater core or the a/c was stuck on the a/c duct, i just pushed it over and now i get hella heat. i ll fix the cable when it gets warm. thanks for the repley.

 

DOD : I'm having the same problem with no heat. Well.... I get a little bit... but not much considering I live in MN and it's below zero quit a bit. Anyways.... I think it may be the same thing. However, my head unit where I control the temp. feels loose or like it's broken. I have a Honda Civic and hopefully getting under the dash to the duct won't be hard.. We'll see