Heat blows through defrost
Thread Starter
Burning Brakes
Joined: Mar 2012
Posts: 769
Likes: 22
From: California
FL Events Coordinator
St. Jude Donor'13
Heat blows through defrost
So finally got my heat fixed on my 1989, at least so I thought. Found and changed a bad blend door motor causing me to only have A/C no matter what. Get the motor changed and finally have heat. However, the heat will only blow through the defroster vents and nothing else. My A/C when set to 60 has no problems and goes through normal vents but once set to anything else it goes to the defrost vents. Let me know what you guys think I should start with. Thank you.
Oil Producer
Joined: Apr 2014
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to see the three way at location HVAC on the above diagram, you may need to pull the dizzy to see it. mine hand broken there. i spliced a small piece of rubber tubing i think it was 5/32 ID and it worked great. i had to peel back my harness that runs behind the engine (all doable with dizzy pulled) to find the piece fo broken vac line.
Oil Producer
Joined: Apr 2014
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Le Mans Master
Joined: Jul 2004
Posts: 6,228
Likes: 698
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
So finally got my heat fixed on my 1989, at least so I thought. Found and changed a bad blend door motor causing me to only have A/C no matter what. Get the motor changed and finally have heat. However, the heat will only blow through the defroster vents and nothing else. My A/C when set to 60 has no problems and goes through normal vents but once set to anything else it goes to the defrost vents. Let me know what you guys think I should start with. Thank you.
Thread Starter
Burning Brakes
Joined: Mar 2012
Posts: 769
Likes: 22
From: California
FL Events Coordinator
St. Jude Donor'13
Also I just noticed something else. Whenever I switch the Head unit to heat (90°) it blows nice cold air out of it trough the defroster and when the unit is set to cold (60°) it blows heat through the normal vents.... anyone got any ideas on this? I’m thinking either the head units is messed up or the person who rebuilt the motor for the blend door screwed up and wired it backwards. I’m thinking I could de-pin the connector and swap the wires around if so. Any thoughts?
Thank you all so much for the help thus far!
Le Mans Master
Joined: Jul 2004
Posts: 6,228
Likes: 698
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
I feel like this might be my problem. I can’t seem to find my manuals due to a recent move but the controller is by the driver side kinda behind the gas pedal correct?
Also I just noticed something else. Whenever I switch the Head unit to heat (90°) it blows nice cold air out of it trough the defroster and when the unit is set to cold (60°) it blows heat through the normal vents.... anyone got any ideas on this? I’m thinking either the head units is messed up or the person who rebuilt the motor for the blend door screwed up and wired it backwards. I’m thinking I could de-pin the connector and swap the wires around if so. Any thoughts?
Thank you all so much for the help thus far!
Thread Starter
Burning Brakes
Joined: Mar 2012
Posts: 769
Likes: 22
From: California
FL Events Coordinator
St. Jude Donor'13
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Thread Starter
Burning Brakes
Joined: Mar 2012
Posts: 769
Likes: 22
From: California
FL Events Coordinator
St. Jude Donor'13
Post 3 and 4 are not my problem from what I can see. I have a good vacuum between the lines. Check with a vacuum pump and holding psi
I Now realize I was confusing the programmer and controller in my head.... sorry about that.
I found that the motor i was sent was wired backwards as swapping the pins in the connector fixed that problem. Still doing some work and trouble shooting on the defrost problem. Just got back from a trip so haven’t had time to play with it.
I Now realize I was confusing the programmer and controller in my head.... sorry about that.
I found that the motor i was sent was wired backwards as swapping the pins in the connector fixed that problem. Still doing some work and trouble shooting on the defrost problem. Just got back from a trip so haven’t had time to play with it.