Water circulating constantly through heater?
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Senior User
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From: Gig Harbor, WA
Water circulating constantly through heater?
It looks like engine coolant is circulating through the heater core when ever the engine is running and the heated air is trapped in the heater plenum until the temperature lever is switched to let it out to the windshield or cab floor. Is there no valve to stop the hot water from going through the heater core? I guess if there was the coolant line resting against the choke wouldn't stay hot. In my Haynes manual it looks like the Bronco does have a cable going to a heater valve.
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From: houston
Your heater control valve should be vac/operated. The reason is that in 1974 all HCV had to default to the open position. The only way to assure that that happened was to make them vac/op. The reason for the open default is to keep the windshield clear in winter or in the rain. It's just a safety feature. My guess is you have a bad vac/line to the HCV. Good luck.
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From: Gig Harbor, WA
This '76 F250 360 has choke heat supplied, in part, by the heater hose being pressed against the plastic choke cap. If coolant was not circulating constantly that hose would not remain hot. There are no vacuum hoses to this non-AC heater control, only two cables, one to direct heat to the floor or the defroster vents and the other to either contain the heat within the heater plenum or let it out depending on how far you move the lever to the right. Can NE1 confirm or discount my idea on this?
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From: SD
Originally Posted by 94van
I think most vehicles have a heater water control valve. It's located in a heater hose under the hood. Some are vacuum operated, some by a cable from the control panel.
76 F250 4X4, you are right, coolant constantly circulates throught the heater core. But with the control to cool, you shouldn't notice any heat.
Marty
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From: Gig Harbor, WA
I just removed a factory AC/heater from a '75 F250 and it had a one bowden cable control which operates a flap which controls temperature just like my non-AC '76 F250. There is no control of temperature by a coolant control valve in either vehicle and coolant circulates constantly through the heater core. Again, I am open to opinions but this is the way it appears to me. I'm only interested in getting this correct because I want to install factory AC in my '76 F250 and do it right.
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From: SD
My 1973 factory manuals show a vacuum operated valve in one of the heater hoses. Also, the a/c system I removed from a '78 (to go into my '73) has a vacuum operated valve in one heater hose. Both are F100 2wds, maybe that makes a difference, or maybe yours was removed from your'75 by a previous owner...
Marty
Marty
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From: Gig Harbor, WA
73custom you are correct. I just returned from the bone yard and a '75 and '76 F250 with factory AC both had a vacuum operated valve in one of the heater hoses even though the non-AC rigs don't. I wonder if all of the factory AC rigs have an electric choke since they wouldn't have a constantly hot heater hose for the extra choke heat.
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