Is there vacuum lines in a 1991 Honda Accord heat system. When I hit the gas pedal the fan motor picks up. The heat also is not as hot on high fan speed. The lower the fan speed the hotter the heat. If there are no vacuum lines what else could cause it.

What i've done: Flushed heater core
Changed thermostat with radiator
inspected heat control valve by firewall
The car is a 1991 Honda Accord 2DR Coupe with 170,000 miles.

Its real annoying when trying to heat up the cab on low fan speed.

 

Have you checked the blend door adjustment......

 

No How would I do that?

 

Can say that it will help but it costs nothing. Pg 15-31 of the manual shows the process.

 

Ok i'll try that and write back.