1997 Ford F-250 No heat but heater core good

AKTYREMAN

MEMBER
1997 FORD F-250
V8
4WD
MANUAL
120,000 MILES

I have tried everything, new heater core, tore apart the dash and all valves are working ok(heating and cooling vents) great air flow, when you reach up in the box it is very warm. You get more heat when its on vent than when on heater. Any ideas?

Thanks

6 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Did you replace the thermostat and also check for a heater control valve that's malfunctioning

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Monday, December 31st, 2018 AT 9:24 AM

AKTYREMAN

MEMBER
3 POSTS

Yep I did, can't find any valves that are malfunctioning, they all seem to open and close right.

Thanks

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Monday, December 31st, 2018 AT 9:24 AM

VERYCOLD

MEMBER
3 POSTS

I had same problem. Replaced thermostat and heater core. Here's all it was. An ink pen.
Take the glove box door off to see the blend door cable. Make sure it appears to be working. Then remove the heater core cover and blend door cable.( I had to loosen up the dash to get the cover out.) Now look inside the plenum and manually move the blend control door from hot to cold. If it doesn't go completely to the left closing off the plenum then you may have a pen or something out of view on the floor of the plenum. Take a wire or hook shape tool and rake it along the bottom next to the door and listen for anything loose.I was able to squeeze my hand in enough to remove it. Check door again and it should go completely closed.

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Monday, December 31st, 2018 AT 9:24 AM