No Heat

Tiny
KICKNCOUNTRY
  • MEMBER
  • 1992 FORD F-150
Heater problem V8 Two Wheel Drive Automatic 150000 miles

I'm trying to narrow down the problem with my truck. I just replaced the thermostat in it thinking that was the problem. Here we go the blower motor for the heat comes on and blows good, however I can not get it to blow out heat. It is just cool air. I do not know if it is the heater control valve or what. I do no smell any anti-freeze inside the cab as if the heater core was leaking.

There isn't a heater control valve in the lines of the heater core. And with the engine running both hose into and out of the heater core were hot. Could this be one of the systems that is ran off of vacum? And if so where is the part that I might need to replace?

I do intend on making a donation to this site when and if I can get this problem resolved.

Thanks for the help,
Earl

Any suggestions?
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Wednesday, January 21st, 2009 AT 8:01 AM

27 Replies

Tiny
KEN
  • ADMIN
If there is no heater valve, the system must work from a "blend door" which is located near the heater core itself. It allows fresh air from the cowl to enter the vehicle, and based on how much heat you want, the blend door allows the air to pass over the core.

Check to make sure there are no cables or vacuum lines running to that area which are disconnected. Also, look for a vent door that appears to regulate the air passing over the heater core itself.

This guide shows the broken vacuum line problem with these trucks.

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

and

https://www.2carpros.com/articles/car-heater-not-working

Here it is for your car (below)

Please let us know what happens.

Cheers, Ken
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Wednesday, October 25th, 2017 AT 9:13 PM
Tiny
BRUCEELLSWOERTH3109
  • MEMBER
  • 1992 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Heater problem
1992 Ford F150 V8 Two Wheel Drive Automatic 150000 miles

I need to know what I need to look at to find out why I do not have any heat.

Thanks for your time
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working! Also the thermostat on a truck this old should be checked.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
RLEIGH59
  • MEMBER
  • 1992 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 121,000 MILES
Heater problem
1992 Ford F150 V8 Two Wheel Drive Automatic 121000 miles

I HAVE REPLACED THE WATERPUMP, THERMOSTAT, NEW FLUSH AND FILL, HOSES ETC. I HAD FLUSHED AND FILLED AND REPLACED THE THERMOSTAT AND THE HEAT WAS FINE. THEN I REPLACED THE WATERPUMP AND NOW THE ENGINE RUNS COOLER AND DOESN'T LEAK BUT NOW MY HEAT IS NOT GOOD. WHAT COULD IT BE? ANY ADVISE?

THANKS
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
BLACKOP555
  • EXPERT
Sounds to me like you may have gotten air trapped in the system. Bleed it out and the problem should go away.

Let me know how it goes.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JMC33
  • MEMBER
  • 1994 FORD F-150
  • 4.9L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 71,000 MILES
Truck has no heat and overheats quickly when driving. Installed new thermostat, water pump and lower rad hose (no spring like old hose). Possible clogged radiator or maybe a bad heater core. Please help, thanks.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
STEVE W.
  • EXPERT
Start it up and let it warm up. Use your hands or a non contact thermometer and check the temperatures of the upper and lower radiator hoses. Also, check the temperature of the heater hoses. What you want to feel/see is all the hoses at close to the same temperatures. With the heater you need to make sure the heater valve is opening. Then both hoses should be hot enough that you do not want to hold them long. Same with the radiator hoses.
In either case if one hose is much hotter than the other you have low/no flow through the core.
Sometimes you can simply flush the system with cooling system flush to clear things out.

But, you also say it gets hot fast. For that I would check for a bad head gasket. Simple combustion gas test would give you a hint of that.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JMC33
  • MEMBER
First off thanks for responding back. So after getting the truck warm I did the hand test on all hoses, etc and found that the lower radiator hose is quite cool and the upper is quite hot. Radiator clogged up?
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
STEVE W.
  • EXPERT
Clogged or you got one of those "new" thermostats that does not work out of the box. BTDT. How about the heater hoses? Are they both getting hot? If yes but no heat, it could be the blend door inside the heater box.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JMC33
  • MEMBER
I was thinking about getting another thermostat. Those two other hoses I noticed one cold and one hot.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
APRIL1980
  • MEMBER
  • 1993 FORD F-150
  • 133,000 MILES
The heater only blows out cold air
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
First, make sure the cooling system is full. Next, start the engine, turn the heat on and allow the engine to warm up to operating temp. Once warm, feel both heater core hoses. Both should be hot. If only one is hot and the other warm, flush the heater core. If both are hot, check to make sure the blend air door is opening. It may be stuck or damaged.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
STEVE W.
  • EXPERT
You could test the original and the new one.
What did the coolant that came out look like? Clearish and clean or murky like mud? One hot one cold can mean a plugged core as well. When you drain it next, grab a hose and try running some water backwards through the core. At least that one has an easy to change core.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
APRIL1980
  • MEMBER
Thank you, I will try this.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JMC33
  • MEMBER
The coolant was in fact brown and nasty.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Let me know what you find.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
STEVE W.
  • EXPERT
What I expected. Sounds like it may have had a dose of sealer added. That crap causes more problems.

I have got a Jeep in at the moment that someone put a couple cans in. Heater core plugs up in a week, not good in 14 degree weather. It is going to get a flush with detergent and acid to try to get the crap out of the system.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
APRIL1980
  • MEMBER
We done what you stated and it still did not work. Flushed it then done a reverse or something like that is what he told me. I think he's gonna take it to a garage to have it fixed. Thanks for the info.
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JMC33
  • MEMBER
Hey Steve so you suggest flushing the radiator out? Should I add anything while doing it?
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Are both hoses getting hot now? Have you checked the blend air door?
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Wednesday, October 25th, 2017 AT 9:15 PM (Merged)

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