Heat starts then stops from dash vents

JPEARSON73

MEMBER
FORD F-150

1997 Ford F-150 4x4, automatic transmission w/approx 150K miles will blow heat through floor vents fine (now) but when you turn it to dash vents it blows hot for about 1 minute then turns cold. I didn't have any heat at first but I have flushed the radiator & core system, replaced the antifreeze & put on a new thermostat. I keep reading about a heater control valve, if my truck has one I can't find where it is & didn't find it in the Chilton book. Does anybody have any suggestions? Thanks for any help.

3 Replies

BLACKOP555

MECHANIC
10,371 POSTS

It is located insdie the heating duccts of the cab. To get at it you have to remove the dash and take off the covers of the ducts to get to it. Its a lengthy job. It is probably sticking due to heat and warping or from a cracked vaccum line or not efficent vaccum reaching the line causing it to waver from hot to cold

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Thursday, October 18th, 2007 AT 9:07 PM

JPEARSON73

MEMBER
3 POSTS

Thanks for the information I will check on this but can you tell me where the vaccum lines are or how to get to them. The Chilton book doesn't have anything about this in there. Also, would you check the vaccum line first before trying to get to the heater control valve. Thanks again.

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Saturday, October 20th, 2007 AT 11:17 AM

BLACKOP555

MECHANIC
10,371 POSTS

Easiest way is to take the heater out of the dash and look youll find the vaccum lines behind there. It may even be a electric motor failing on it. But im pretty sure its vaccum related.

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Saturday, October 20th, 2007 AT 12:36 PM