Heater fan malfunction

[Pinecone]

Sent: 10/24/2007

Greetings from Montana.  With winter coming on, (snow predicted tomorrow, 60%), I need to get my heater fan fixed.  It runs okay until I start to climb a hill then it quits blowing.  Help is appreciated, ideas are welcome.  It's in a 460 Ford chassis, 1991

[ontheroadagain]

Sent: 10/24/2007

does the fan motor actually stop blowing or does it just blows out at the floor? the door controllers in the heater box operate on vacuum from the engine and if the check valve on the supply line goes bad you will loose vacuum during heavy acceleration and the doors will open or close and shut off the heat the vacuum line and check valve are usually under the hood on the passengers side near the blower/heater box

[Pinecone]

Sent: 10/24/2007

The fan shut off.  No air comes out.  When I go down the hill, the warm air begins to return.

[firehart2]

Sent: 10/24/2007 8:06 PM

On my 95 Ford PU the vacuum line to the control valve dried up and broke. Now the heater is on all the time. Sounds like you might have a loose wire.