Heat in the cab
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Posting Guru
Joined: Dec 2009
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From: Dairy, OR
Heat in the cab
Hey guys I need some help. I just took our first real big trip in the truck, drove from southern Oregon up to the middle of Washington and then down the Washington/Oregon coast. Only problem I had on the whole trip was it the heat in the cab, mainly off the drivers side! It was like the heater was stuck on hot and blowing at full fan speed right at my feet. It was the worst when climbing under load... 6200 lb RV up an 8% grade with it being 90 degrees outside wasn't much fun!
I have checked all the heater connections etc and everything seems to be working properly, heater and AC both work fine. I am thinking this was heat off the exhaust but not sure. I know this was an engine swap truck when I got it, so my question is... is there some sort of heat shroud that might be missing and causing this heat? Honestly I am grasping at straws here, anyone got any ideas then I want to hear them!
I have checked all the heater connections etc and everything seems to be working properly, heater and AC both work fine. I am thinking this was heat off the exhaust but not sure. I know this was an engine swap truck when I got it, so my question is... is there some sort of heat shroud that might be missing and causing this heat? Honestly I am grasping at straws here, anyone got any ideas then I want to hear them!
Posting Guru
Joined: Dec 2009
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Glad you had a good trip Ozz.. I think you may need a shut off valve on the heater hoses,air going past the heater core will funnell right down towards the floor,Mine did that till the heater core busted then I bypassed it for a while and the heat went away. Just an Idea
Fleet Owner
Joined: Jul 2006
Posts: 20,362
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From: Mi'kma'ki
when you turn the a/c on,do you hear a really loud "thump!!" like it means it? its quite loud and very forceful,and will be coming from the passengers side feet area,up under the dash.
off topic:
"6200 lb RV up an 8% grade with it being 90 degrees outside wasn't much fun!"
did your engine fan kick on while hauling this in these temps? (nothing to do with you a/c problem.)
off topic:
"6200 lb RV up an 8% grade with it being 90 degrees outside wasn't much fun!"
did your engine fan kick on while hauling this in these temps? (nothing to do with you a/c problem.)
Thread Starter
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Posting Guru
Joined: Dec 2009
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From: Dairy, OR
I haven't noticed a loud thump as you describe it. What is that??
Yea clutch fan was kicking in fine, hottest the truck ever hit was about 212 degrees then fan would kick on and cool her right down.
Yea clutch fan was kicking in fine, hottest the truck ever hit was about 212 degrees then fan would kick on and cool her right down.
Fleet Owner
Joined: Jul 2006
Posts: 20,362
Likes: 823
From: Mi'kma'ki
yeah ok.that's what i figured your problem was.
there's a trap door in the ducting there,that seals off the heater core.if that doesn't get closed,forget it.you'll have your a/c on full tilt,and still be cooked alive lol.
you need to make this door closes again.the most common problem is the hose that connects to the...........ahh.you know what.im sure i can find a thread,possibly with pics that can explain this even better than i can.......
hang on.
there's a trap door in the ducting there,that seals off the heater core.if that doesn't get closed,forget it.you'll have your a/c on full tilt,and still be cooked alive lol.
you need to make this door closes again.the most common problem is the hose that connects to the...........ahh.you know what.im sure i can find a thread,possibly with pics that can explain this even better than i can.......
hang on.
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Fleet Owner
Joined: Jul 2006
Posts: 20,362
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From: Mi'kma'ki
heres one.no pics though dangit.
but this will get you on the path to success warozz:
https://www.ford-trucks.com/forums/8...ater-core.html
if it turns out to actually be the blend door itself.....well,your not hearing the thump of it close at all...i was just gunna say,if it no longer seals tight,you'd want to just bypass the heater core for the summer,or install a shut off.-a good mod in itself anyway.but it's likely you have a problem with just getting the thing to close,let alone a tight seal problem.
you'll see the problem soon enough.
ahh i found one.:
from another good thread that will help you:
https://www.ford-trucks.com/forums/8...rom-vents.html
i just got my a/c working yesterday warozz.one of the first things i listened for was that thump.was happy to hear it.very loud and distinct when you have a nice seal there.
but this will get you on the path to success warozz:
https://www.ford-trucks.com/forums/8...ater-core.html
if it turns out to actually be the blend door itself.....well,your not hearing the thump of it close at all...i was just gunna say,if it no longer seals tight,you'd want to just bypass the heater core for the summer,or install a shut off.-a good mod in itself anyway.but it's likely you have a problem with just getting the thing to close,let alone a tight seal problem.
you'll see the problem soon enough.
ahh i found one.:
from another good thread that will help you:
https://www.ford-trucks.com/forums/8...rom-vents.html
i just got my a/c working yesterday warozz.one of the first things i listened for was that thump.was happy to hear it.very loud and distinct when you have a nice seal there.
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Postmaster
Joined: Apr 2008
Posts: 4,802
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Guys, there is a vacuum-controlled heater core bypass valve that can be installed, it's normally found on Rangers but our trucks can use it too - here's the article you need to read for this:
Heater Core Bypass
I did this mod a while back and noticed no improvements at all, but my blend door seals very very good, others with not so perfect seals have reported that A/C did actually get colder after the bypass valve was installed.
Heater Core Bypass
I did this mod a while back and noticed no improvements at all, but my blend door seals very very good, others with not so perfect seals have reported that A/C did actually get colder after the bypass valve was installed.
Elder User
Joined: Apr 2002
Posts: 950
Likes: 2
From: West Bend
Engine swap truck? Was the previous engine a gas EFI? My truck is using an EFI cab from an '88 and the ECU plug came through the drivers side firewall right by your left foot. If the ECU was pulled and the plug undone you'll have about a 1.25" wide by 5" tall hole through the firewall left over from the gasser EFI.
Elder User
Joined: Apr 2002
Posts: 950
Likes: 2
From: West Bend
lol, I used mine to run wire through as well, however when I redid all this stuff I ran 'em through a grommet so I could seal up the hole 
it lets a lot of hot air in during summer and a lot of cold air in during winter
it lets a lot of hot air in during summer and a lot of cold air in during winter
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
Coolant does circulate through the heater core at all times when the engine is running.
There is a door in the heater that shuts air flow across the heater core to control the temperature that is probably leaking air.
But a shut off valve in the coolant lines does a much better job.
Also you may have a couple holes through the firewall for wires that have no grommets or the grommets are damaged, letting even more heat from the engine compartment in.
There is a door in the heater that shuts air flow across the heater core to control the temperature that is probably leaking air.
But a shut off valve in the coolant lines does a much better job.
Also you may have a couple holes through the firewall for wires that have no grommets or the grommets are damaged, letting even more heat from the engine compartment in.