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Jan 23, 2013 | 06:17 PM

benbuilder

Thread Starter

Fleet Mechanic

Joined: Sep 2012

Posts: 1,605

Likes: 52

no heat

1975 ford f100. 1980 302 motor. I have no heat or defrost. The air blows, but cold. Temp sending unit shows a warm engine. I replaced the thermostat about a month ago. At the same time I blew out the line to the heater core. It was clogged. I just checked the two lines going to the heater core. One is hot the other cold. I guess it means either the core is clogged or a line is correct? How could this happen so quickly? I should blow out the line again, right? Its 3degrees right now and its my daughters truck. Any ideas? It is her first winter with the truck. It is new to her as she bought it this past october. Thoughts?

Jan 23, 2013 | 06:44 PM

bucks77ford

Post Fiend

Joined: Jan 2006

Posts: 5,037

Likes: 9

From: Kasson, Minnesota

It could be the vacuum heater control valve is not opening.

Jan 23, 2013 | 07:07 PM

irydasteelhorse

Tuned

Joined: Nov 2012

Posts: 253

Likes: 51

From: billings mt

it could be as simple as low on prestone..........it wont circulate if there isnt enough in there!

Jan 23, 2013 | 08:25 PM

benbuilder

Thread Starter

Fleet Mechanic

Joined: Sep 2012

Posts: 1,605

Likes: 52

No heat

I checked that already. thanks. I will research the vacuum heater control valve now and see if I can figure out what it is.

Jan 23, 2013 | 08:28 PM

gnwalker

Elder User

Joined: Apr 2004

Posts: 630

Likes: 0

From: Hedgesville WV

The lines could be reversed if nobody was paying attention during the motor swap. It happened to me.....

Jan 23, 2013 | 09:22 PM

Randy Obrien

Freshman User

Joined: Jan 2013

Posts: 30

Likes: 0

From: nebraska

i pull both heater hoses off the heater core and blow it out then fill the heater core with vinegar and let it soak for 20 min or so and then flush it both ways and blow it out. if i get a lot of crap out of the heater core i flush the engine and radiator as well so it dont plug up again right away. most poeple use tap water to mix antifreeze and lime will build up and plug a heater core.

Last edited by Randy Obrien; Jan 24, 2013 at 07:32 AM. Reason: typo