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Discussion Starter #1
2001 Ford F150. Rarely driven in the winter unless there are heavy snows. As such I always start it up once a week and let it idle for 30 min. to keep the battery charged. Last week after letting it idle I noticed the heater was blowing cold. Could it be the thermostat, or any thing a backyard mechanic could fix?
 

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was your temperature gauge 1/2 way up like it normally would be?

Does this F150 have electronic temp control (digital)?

or does it have the knobs you crank for heat & cold?
 

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Temp gauge halfway, manual heat adjust, can hear the valve changing when I switch from vent to heat to defrost.
 

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check your hose to see if its building pressurewhile its warming up that will tell you if your thermostat is stuck open
 

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If your temp gauge is going up to normal range, then it is not likely a stuck thermostat. Even a stuck open thermostat will produce some heat through the heater. How often to you change the coolant in this little used vehicle? If not regularly, it could be a clogged heater core. Not ease to fix. Even though you hear the air flow valve change, it is possible the cable that controls the valve to let radiator water flow through the heater core may be stuck or the cable to that valve may have broken. I do not know enough about that particular engine compartment layout as to whether that valve is visible and you could have someone watch it while you manipulate the temp lever in the cab.
 

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If the temp gauge is showing warm temps....hop in the truck for a moment and bring the idle speed up to like 2000 to 2500 rpm and if you start getting heat then it might be an impeller that is getting worn down and thus not moving the coolant effectively. I had this happen in my 2004 Ford last year. Also double check your coolant level. If you don't have adequate coolant in the system you might have gotten an air blockage and need to bleed the air out of the system.
 

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If the temp gauge is showing warm temps....hop in the truck for a moment and bring the idle speed up to like 2000 to 2500 rpm and if you start getting heat then it might be an impeller that is getting worn down and thus not moving the coolant effectively. I had this happen in my 2004 Ford last year. Also double check your coolant level. If you don't have adequate coolant in the system you might have gotten an air blockage and need to bleed the air out of the system.
:th_greatpostsign: First thing to check is your coolant level. Most of the time, notice I said most, the lack of heat is attributed to low coolant. Manual heater door operation takes out any electric door actuators, and you state you can hear it move, so..... Haven't seen blocked heater cores as much as earlier cars now a days. Getting more technical, you'd get into your water pumps, and headgasket issues, but never overlook the simple things first. Another thing to check after the coolant level, is feel the heater hoses at the firewall when it is up to temp, and see if they are both hot. Inlet will be hotter than the outlet, but cold will tell you if you have a problem with an air vacuum lock, or possibly if you have a blockage.
 

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I have a 95 F150. Had a similar problem but on the AC side. Is the control a vacuum system? Check for a vacuum system leak as it may be the door system in the heater housing that is not operating correctly due to a vacuum leak.
 

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I would replace the heater control valve, just because you "hear" movement doesn't necessarily mean the valve itself is opening, they're cheap plastic and prone to breaking internally. Still have an 1994 Explorer (beater mobile) it did the same thing to me, changed heater control valve for $15, problem solved!
 

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I just encountered this problem yesterday on my Ford Ranger. Had some work done on my truck. Hose left disconnected. Immediately fixed and fluid replaced. But my heater at first wouldn't blow hot. Turned motor off and restarted and it worked. Mechanic said there is something like an auto mixer that probably had to reset. Never heard of this, but thought I'd pass it on. Even tho they 4got to put my radiater hose back on after replacing belt pullies, I've used this shop for about 12 years and they've always steered me right and been honest. Worth checking out maybe.
 

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Check coolant, next check both heater hoses, one in one out if one is warm/hot the other is cold then it is the heater control valve or the cable could have came off or the clamp that holds the outside of the cable could be loose and letting the whole cable move instead of just the inside cable thus not opining the heater valve, as some one else said it could be a vacuum hose off and not building vacuum this is most likely the problem, i doubt that for that year it would be a cable.
 

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Canyon Man you may be on to something. Before it got cold my power steering pump locked, shredded the belt and had to be replaced. I'll check the levels and the hoses tomorrow after work, thanks for al the help every one!
 

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Can't check the radiator level like you could in the old days the container off to the side is several inches below the cold fill line. checked the 2 hoses going into the firewall, 1 is hot the other is cool but not cold. also noticed after 40 min. the air was also cool but not cold so took off down the road and the air would blow lukewarm then cool then lukewarm again. Looks like it is low fluid level. el like a dope for overlooking an obvious troubleshooting step.
 

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Poured nearly a gallon of premixed antifreeze into the radiator, let her warm and up and drove down the road, and by the time I got to the highway she was nice and toasty. Problem solved. Again thanks for everyone's help. Not only saved me a few bucks but now I have a backup in case my wife's ride decides to crap out at O Dark Hundred next Monday when we head down to visit family.
 

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For engine (and exhaust system) longevity, strongly suggest that you drive it 30 minutes instead. Or at least idle 15 then drive 15. Getting an engine fully up to temperature before storage is perhaps the most important thing you can do for its health.
 

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Poured nearly a gallon of premixed antifreeze into the radiator, let her warm and up and drove down the road, and by the time I got to the highway she was nice and toasty. Problem solved. Again thanks for everyone's help. Not only saved me a few bucks but now I have a backup in case my wife's ride decides to crap out at O Dark Hundred next Monday when we head down to visit family.

Well hang on a second here - Problem not really solved. That antifreeze went somewhere. It's a sealed system. Dripped out of a water pump? Dripped out of a Thermostat gasket? No leaks, no drips? If so is the exhaust white only when 1st started (indicating coolant is getting into the cylinders)??
 

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Could have been so low on coolant that it just circulated into the system, just try adding more and you should be ok. If you aren't seeing that much fluid disappear through a leak then it probably just circulated into the system.
 
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