1999 Ford F150 Heater Just Blows Warm

Gary from Muleshoe · Dec 3, 2016

My 99 F150 heater just seems to blow warm. I have already check the mixing door and it is working properly. (I cut an access hole to get to
it.) I have also checked the heater hoses and they both seem to be the same temperature after driving for 30 miles, which is very hot to touch. The temperature switch is
working properly. If the blower is on hi it seems blow cooler than when it is on the low speed. Any suggestions, I have searched Google and
not come up with anything. Thanks in advance. Gary

Gary from Muleshoe · Dec 3, 2016

I forgot to ad is has a new thermostat in it as well.

centash · Dec 3, 2016

Clogged heater core?inside and outside? Ben

John730D · Dec 3, 2016

Clogged heated core. Might try back flushing (first) or running a cooling system cleaner through it.

js305 · Dec 3, 2016

I have the same problem with my '01 Dodge pickup. However, I did it by putting various things in it to keep it from leaking. I get warm air, enough to work the defroster OK, but I am not going to get too hot in there on a cold day.

The reason I'm replying to this is that on mine, replacing the heater core is a royal pain, expensive to have it done, and not something I want to tackle myself.

Have you had any smell, or leaks? Back flushing the core might clear it out some, but if there is any corrosion or pin holes in it they will show up then.

And, as a side note, we are neighbors in a way, I live about four miles east of Lubbock.

Gary from Muleshoe · Dec 3, 2016

Thanks for your reply, I have checked for leaks and found none. When I had it in the shop for overheating they flushed the entire system. I may have to back flush the heater core though. It is just a weekend driver so I am in no hurry.

Glad to know someone close by is on here. I have a son that lives in Shallowater. He is an HVAC guy, we do a little side work together now and then.

Also thanks for all the other replies as well.

Steve@Advance · Dec 3, 2016

Gary, sounds like lack of airflow through the heater core. Since both hoses are very hot, you have coolant circulation, but the heat isn't being removed from the core.

There is also a damper door that sends air to either the heater or evaporator. Be sure it is working, not jammed (things falling down the defrost holes), or the servo not making the full stroke (could be vacuum or electric), or something broken, plastic levers, hinges, etc.

Another cause could be the airflow is blocked by leaves or mouse nests stuck to the core, clogged cabin air filter (if equipped), or leaves trapped in the blower wheel.

shaun wallace · Dec 3, 2016

I have same problem on 99 chevy with both heat and ac. Come to conclusion stopped up with good ole west tx dirt.

old · Dec 3, 2016

You might try switching the heater hoses around so the flow is going backward of what it is doing now and if that helps then the core was clogged up. I have done tha tin the past and that fixed the problem and moved what ever was blocking it out. Or it could be the out side air inside air door not closing off to have you reheating the inside air and pulling in the cold out side air

Brown Swiss · Dec 3, 2016

Check the fuse for the cruise control!

BushogPapa · Dec 3, 2016

Was it a 195 degree thermostat..?

If not, the heater may not get all that hot..

1999 Ford F150 Heater Just Blows Warm

Gary from Muleshoe

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Gary from Muleshoe

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centash

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John730D

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js305

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Gary from Muleshoe

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Steve@Advance

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shaun wallace

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old

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