Is the heat on?

[Number21]

Now that it's getting warmer I'm noticing the inside of my truck is getting hot when I have the windows closed. (at night) The heat is turned off and set to cold, but I still feel like it's on a little bit. I know the blower fan always blows even in the "off" position, is that making the heat? I'm not quite sure if it's coming from the HVAC or just through the firewall.

Anyway, does it sound like maybe my heat controls aren't turning off all the way? I'm wondering if maybe I should install a valve to shut off the heater core for the summer....

[rwhit57]

My blower does not run in the off position.

[Mrknowitall]

in the 60's people died from lack of oxygen with windows up.
chevy fixed this by constantly running the fan to pump in fresh oxygen.

turn your controls to cool to avoid drawing air from the heater core, other than that u can just disconnect the blower in summer but i wouldent recommend it due to.......uggh....dying.

also chevy made the fan run to keep the heater core cool to get more life out of it, however here in the valley when its 110f out side, its killer...

my non ac truck always has the windows down so im used to it..... i suggest u just leave it alone.

[Mrknowitall]

Originally Posted by rwhit57

My blower does not run in the off position.

then a resistor has went out or some one did the white wire mod or whatever its called

[rwhit57]

Originally Posted by Mrknowitall

then a resistor has went out or some one did the white wire mod or whatever its called

My truck is an 85 with A/C and when the selector switch is moved to Off, the fan shuts off. Any other setting it comes on and all speeds work fine. I don't know what years they ran continuously or if it was non A/C trucks. The people dying story and the heater core thing sound a little bizarre, for gosh sakes did they not know how to roll down the windows in the 60's? Maybe it was the gas tank mounted in the cab, they certainly fixed that well by mounting it outside the frame rails. Maybe it's true but I've never heard of that being the reasons.

[big10ratrod77]

my 77 did run all the time but i put a cheap on/off switch under the stering column and cut the power wire for the bower motor and ran it through the switch works like a champ

[old Rusty C10]

the only time the fan motor blows is when the ignition switch is on the on position
some vehicles had low as the lowest setting others had off if you have off the blower motor should be not turning

[76stepsidechevy]

Theres always coolant running through that heater core so some heat will always make it in especially with the fan always running. Ive seen people run a bypass or plumb in valves for the warm months.

[J Knight]

Most big trucks like mine (Peterbilt) have heater core shut off valves to cut off coolant to the heater core for summer months, this is an option you could try to remove excess heat from your cab. In all likely hood I would bet its you blender door not sealing good or operating properly.
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[jjzepplin]

Could be junk and leaves blocking your "core bypass door" which is what I call it. Your levers have a cable or stiff wire that actuates this flapper door that switches from outside air to heat. It can get blocked with junk and not close or it can rust and have a hole in it.

[donut]

Originally Posted by 76stepsidechevy

Theres always coolant running through that heater core so some heat will always make it in especially with the fan always running. Ive seen people run a bypass or plumb in valves for the warm months.

Correct, as far as the heat in the summer, if you don't want to bypass it or install AC, suck it up cupcake.

All of mine have done this, one of the little "penalties" of owning an older truck.

[yousesteers]

My 79, 81, and current 84 the blower did not run roll the windows down if it gets hot or open the lower vents on each side

[CoggedBelt75]

Here is what I use on my 5/8" heater hose. Picked it up at the local auto parts store several years ago for less than 10 bucks. Turned off in the spring and back on during the winter months. Makes a world of a difference during our hot Oklahoma summers.

[Number21]

Thanks for the replies everyone...I think I have a 3/4" ball valve out in the garage, I'll try and plumb that into the heater core.

[motornut]

Originally Posted by CoggedBelt75

Here is what I use on my 5/8" heater hose. Picked it up at the local auto parts store several years ago for less than 10 bucks. Turned off in the spring and back on during the winter months. Makes a world of a difference during our hot Oklahoma summers.

good idea
but caught in traffic i like to put the heat on,if i see it climbing and no air flow threw the rad
just cut the low speed wire on the fan
78 has three speed fan,79 has 4 speed both mine now have off

[Number21]

I used to have a Jeep like that...year round heat to keep the engine cool. Honestly I don't think I've ever seen the gauge in my truck even get to the half mark. I've got a big block radiator/fan and no fan clutch so there's always air flow.

[motornut]

han't seen mine over half but thats what i do sitting in traffic

Did you know
in the air box there is 3 ajustment holes for the def/floor air flow
66% def or floor with 33% always the other way
or 100% up or down

that would mean if the fan is always on ,it's always flowing threw it
and looking on lmc i can't find a pic....