no heat

Reply Subscribe

Thread Tools

Search this Thread

Jan 3, 2012 | 05:52 PM

ricbyrdmay68

Thread Starter

New User

Joined: Jan 2012

Posts: 2

Likes: 0

no heat

I have a 1999 f-150 with no heat, I can get heat for about 20 seconds and then cold air over rides the hot but I can still feel a little heat in there. Two years ago I replaced the blend door with an after market two piece so I didnt have to remove the dash. Now I have removed the panel I cut out of the plentum box to replace the door, I can see the blend door open and close when I turn the temp. select ****, so I know the door, the acuator and the **** are all good. Both hoses are hot going to the heater core and the heater core is hot all over 200 degrees, I can wacth the outside air inlet door open and close, but I am still getting cold air, like the evaporator core is cold and blowing cold air over the heater core, this air is ice cold , really stumped on this one.

Jan 3, 2012 | 09:38 PM

steve(ill)

Hotshot

Joined: Jul 2005

Posts: 11,931

Likes: 180

I think i would take the heater hoses off and connect a garden hose to one side and run it thru and see that you have good flow. If the blend door is open to heat, and the core is 200 degrees you have to get heat. Im guessing your not getting the core hot. Some water flow thru the core,so hoses are hot, but not enough to heat the core ????

Jan 3, 2012 | 10:04 PM

KarleyD89

New User

Joined: Jan 2012

Posts: 3

Likes: 0

I'm in the same position. I have replaced the thermostat twice thinking faulty t-stat, and cleaned out the heater core and had a good flow. Chcked all the hoses and the temps were good. I'm stuck! help please

Jan 4, 2012 | 05:59 PM

ricbyrdmay68

Thread Starter

New User

Joined: Jan 2012

Posts: 2

Likes: 0

done it all

I have done the hoses thats whats getting me I have been through everything and still no heat, coming across the evaporator core it is freezing like the ac is on and then that freezing air is blowing across the heater core and I am onlly getting 69 to 70 degree air in the cab, not to warm when it's 19 degrees outside is there any way to cut the evaporator core on and off?

Jan 4, 2012 | 06:09 PM

steve(ill)

Hotshot

Joined: Jul 2005

Posts: 11,931

Likes: 180

pull the electrical plug off the freon compressor and the AC wont work-- see if that helps.

Jan 5, 2012 | 09:08 AM

KarleyD89

New User

Joined: Jan 2012

Posts: 3

Likes: 0

I thought you only do that if the compressor is going?

Jan 5, 2012 | 09:10 PM

steve(ill)

Hotshot

Joined: Jul 2005

Posts: 11,931

Likes: 180

if there is freezing cold air coming across the evaporator coil, he could have other problmes. The compressor does run when you have the heater on, defrost on, etc.. It drys the air. Just one more test to eliminate a possible problem.... Could also be that crud has settled int eh bottom half of the heater core,. You still have flow thru the top, but not enough fin capacity to transer adequate heat to the air... just a thought.