No Heat
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Freshman User
Joined: Oct 2010
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No Heat
I am trying to figure out why there isn't any heat coming out of the vents.
I have replaced the Thermostat in the truck. I think the engine is getting up to operational temps but still no heat.
I am wondering if the heater switch on the dash isn't opening the flap.
Any ideas on what to check next? Where do I find this flap door that lets heat in?
1980 truck
No AC
I have replaced the Thermostat in the truck. I think the engine is getting up to operational temps but still no heat.
I am wondering if the heater switch on the dash isn't opening the flap.
Any ideas on what to check next? Where do I find this flap door that lets heat in?
1980 truck
No AC
Senior User
Joined: Sep 2009
Posts: 459
Likes: 0
If there's no A/C, the heater switch on the dash will be actuated by a cable on top of the heater box on the engine side of the firewall. Verify that by having a helper move the cable.
The door is controlled 100% by the little arm that sticks out the top.
The heater core may be bypassed either with a tube that connects the two ends or someone may have installed a block. Trace the hoses between the heater core and the water pump to verify.
The door is controlled 100% by the little arm that sticks out the top.
The heater core may be bypassed either with a tube that connects the two ends or someone may have installed a block. Trace the hoses between the heater core and the water pump to verify.
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
Warm up your engine and feel the heater hoses under the hood where they connect to the
heater core in the heater box. If they're warm, the heater core is gonna be warm, too.
Given the rather sudden appearance of this problem, I agree with the above poster - check
that cable and its operation of the flap inside the heater box. those cables are known to snap
and you might just manually move that flap into the right position to get warm air out the
heater inside the truck until you figure out how to deal with the problem.
heater core in the heater box. If they're warm, the heater core is gonna be warm, too.
Given the rather sudden appearance of this problem, I agree with the above poster - check
that cable and its operation of the flap inside the heater box. those cables are known to snap
and you might just manually move that flap into the right position to get warm air out the
heater inside the truck until you figure out how to deal with the problem.
Moderator
Joined: Jan 2001
Posts: 56,980
Likes: 2,735
From: Virginia
My old 80 suddenly didn't have heat going to work one morning. About a couple of miles later there was steam rolling out under the hood. Guess what? I forgot to check the anti-freeze level in the coolant, and it froze up on me. Luckily it didn't hurt anything.
Elder User
Joined: Nov 2010
Posts: 536
Likes: 2
From: Jacksonville, NC
Something else to check is the resistor. For the longest time, my heat wasn't working either. Wouldn't even turn on. I unplugged the wires from the resistor, put a jumper wire in the two terminals in the plug and the heat started working. I'll post pictures of it tomorrow..
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the Pelon
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Jan 9, 2005 04:33 PM
