Heater Not Working

Tiny
WIZARD6768
  • MEMBER
  • 1999 FORD F-150
  • 6 CYL
  • 2WD
  • MANUAL
  • 148,000 MILES
I have a 1999 Ford F150 and my heater has stopped working. The A/C works fine, but when I put it over to heat it stays cold. It does the same thing on defrost - only blows cold.
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Tuesday, November 17th, 2009 AT 11:08 AM

86 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
It sounds like a problem with the blend door. It is a vent door that changes things from AC to heat.

This guide can help as well

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

Joe
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Tuesday, November 17th, 2009 AT 5:22 PM
Tiny
DBAKER1065
  • MEMBER
  • 1999 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 121,000 MILES
All of a sudden I don't get any heat, what could be the problem? Ac works blower works just no heat
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Engine temp O.K. if not thermostat stuck open. If temp good then a blend door problem.

Here is a guide to help

https://www.2carpros.com/articles/car-heater-not-working
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
PAULA D.
  • MEMBER
My problem was the temperature knob. It had a small crack on the inside which loosened it just enough so it wasn't grabbing hold when you turned it to the right. Just in case you're stumped. It's nice when it's something simple!
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
BARBIEG2006
  • MEMBER
  • 1997 FORD F-150
  • V8
  • 2WD
  • MANUAL
  • 24,000 MILES
I have changed thermostat (2) coolant full, replaced fan clutch, just keeps one temperature all the time, no idiot lights on, never gets hot. Is their a temperature sensor on this engine for that? I have 4.6 Ltr.
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi:
Do you mean the engine never warms up or the heater?

Joe
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
BARBIEG2006
  • MEMBER
The heater never changes temperature. Luke warm
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi:
It sounds like the blend door isn't opening far enough. It is located near the heater core. Air from the cowl comes in and the door determines how much air can go past the heater core to warm the vehicle.
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Tuesday, November 27th, 2018 AT 12:35 PM (Merged)
Tiny
SPIKE1846
  • MEMBER
  • 1999 FORD F-150
  • 6 CYL
  • 2WD
  • MANUAL
I have a 1999 Ford F-150 with 199k miles and in July had to replace the water pump (brand new O.E.M.), As the breather hole was seaping water. Had it replaced. Everything was good. About a week ago, it got cold and turned on the heater and it didn't get to warm. Day before yesterday, the engine temp started running hot (never reached overheat, because I turned on heater with blower on high). No heat came out of the vents, but the engine cooled down to normal. I suspected the thermostat, as it had never been changed to my knowledge. It still overheats and the heater just gets a little warm. I suspect that it may be the water pump causing the problem. I did check the radiator and flushed the system out, while I had the cooling system open. I, also, pulled the heater hoses and flushed out the heater core. I do my own mechanic work with the proper tools. I am baffled as to why it is overheating. One thing that I noticed when it started overheating, is that when I released the pressure cap, the tempature did immedeatly go back to normal, which shows the sign of a blown head gasket from the water jacket to a cylinder, but no other symptoms (rough idle or white smoke out the tail pipe).
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
GTECHENGNR
  • MEMBER
My 2002 Nissan Sentra (150k miles) is acting similarly. No blown Head Gasket, Water Pump and Thermostat are good.
.
Does not happen everytime, but maybe once or twice a month. When this happens the engine will get Hot (close to the "H") but the temp will go up and down between 2/3 hot and hot (thermostat opening and closing).
.
What I have noticed when this happens is that my Overflow tank gets completely full. Like your truck, if I crack the Radiator cap, to vent, the cooling begins acting normally and the heater works fine. The last time it happened, I pulled over, vented the radiator, and literally blew into the overflow tank to get the fluid back into my radiator. Hunky-Dorey after that so far.
.
Several mechanic friends of mine are stumped. I have had my Radiator and Cap pressure tested, and they're fine.
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My best guess is there is some kind of "vapor" lock, or maybe reverse vacuum, that keeps the water in the radiator when the Theromstat opens for the first time. From then on the fluid just goes into the over flow.
.
I am going to try "back filling" my system by removing the thermostat and then the lower hose from the radiator and pouring coolant into the hose until the hose (and hopefully engine) is full. Reconnect the lower radiator hose and thermostat, and then top off the radiator.
.
Hopefully, with the cooling system truly "filled" I won't have this vacuum or vapor lock issue any more.
.
Still trying to figure this one out. It's ridiculous to have an over heated engine whole you're freezing you tail off inside the vehicle.
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
SPIKE1846
  • MEMBER
I found my problem. It was in fact the radiator cap. Replaced it, even though it tested out fine. No more problem. For the first guy that answered me, sound like the problem that you are having is the lower radiato hose is collapsing. Either replace it, or as an option that works, take a metal coat hanger and wrap it around a shovel handle until it looks like a spring and slide it into the hose. What this will do is keep the hose from collapsing completely, allowing water flow and not ceiser of flow. This will prevent this from occurring. Hope that this helps.
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
BSKMBA
  • MEMBER
  • 1997 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 191,000 MILES
97 ford f150 4x4 5.4L, heater blows luke warm but not hot. Already changed the thermostat. What would keep it from blowing hot?
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Start the engine, turn the heat on high, and let the engine warm up. Once it is at normal operating temp, feel both heater core hoses. Both should be hot. If they are both hot, check and repair the blend air door. Of only one gets hot, flush the heater core.
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
PESMITH
  • MEMBER
  • 1997 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
No heat is coming from the heater. It has been suggested that this is the thermostat. Another has suggested some type valve that clamps off the heater? Any help appreciated. Thanks in advance.
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Thermostat could be stuck open/heater hoses and heater core clogged-up and defective heater control valve
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
DMYNARD
  • MEMBER
  • 1998 FORD F-150
  • 4.6L
  • V8
  • 4WD
  • AUTOMATIC
  • 199,000 MILES
I have had the heater core, radiator and engine flushed. Having had a 195 degree thermostat installed of course with new coolant. I replaced the temperature control switch on the dash panel. I have also cut a hole in the blend door housing and visually checked the operation of both the actuator motor and blending door both work fine. The temperature of both heater hoses at the fire wall is around 156 degrees. I still have no heat in the interior of the pickup truck cab.
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
DR LOOT
  • EXPERT
Remove the two heater hoses from the heater core and blow through one of them and see if the heater core is plugged? They heater hoses may be heating up from the opposite direction instead of circulation
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Tuesday, November 27th, 2018 AT 12:36 PM (Merged)
Tiny
1999 FORD XLT TRUCK
  • MEMBER
  • 1999 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
In the summer heater works fine. In winter the heater blows cold air only. Replaced thermal switch on dash board. Checked heater core hoses under hood they are both hot when engine is at normal op. Temp.
Signed, cold feet
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Tuesday, November 27th, 2018 AT 12:37 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check and test the thermostat and the heater control valve
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Tuesday, November 27th, 2018 AT 12:37 PM (Merged)
Tiny
JDL
  • EXPERT
Welcome to the forum, I'd have to check the blend door in picture. With the blend door in one position, ac, other position, the air has to go through the heater core.


http://www.2carpros.com/forum/automotive_pictures/170934_blend_doors_1.jpg

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Tuesday, November 27th, 2018 AT 12:37 PM (Merged)

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