Here is the situation:

1997 F150 that does not get very hot when the heater is on. (about 80 degrees) The Defroster is totally cool air - will be a real problem when it freezes out.

I changed the thermostat first - not it. Antifreeze is not great - pretty nasty and needs changing, I know. But I dont think that is it.

Then I started zero-ing in on the Blend Door. But before I bought the Blend Door Kit I cut into the Heater Box to see if that was it - the Blend Door works fine - it is not flopping around. Firm on the spindle - smooth operating.

While I have been working on this problem I have discovered that when I turn the Mode to Floor, Panel+Floor, Defrost, etc - the Air Conditioner Compressor comes on - blowing cold air while the heater is trying to blow hot air. Only "Panel" turns off the AC compressor and gives me 80 degree heat - which is still only so-so heat.

I thought maybe the door that opens and closes to change the Mode - was the culprit. So I took off the radio bezel and felt down in the duct.

When I change the mode, the door opens and closes though it is hard to know if it is doing it properly by touch - but it is firm and not broken or anything as best I can tell.

So, what in the world is the problem here?

Is it the Mode Switch on the Control Cluster? Do they go bad? That is all I can figure. The AC coming on all the time has got me scratching my head.

I took the vacuum lines off and put them back on, messed with the lines down below near the floor - I hear no hissing or anything. Don't really know how to check beyond that.

Is the AC supposed to come ON in almost every Mode? Surely not for "Floor" heat.

But I am getting close to having to take this to the shop - your expertise will be appreciated greatly.

 

If you're confident the blend door is working - suggest to check the heater core. Are both hoses hot and approximately the same temperature? Since you said your coolant was 'nasty', wondering if you don't have a core blockage?? The heater should be able to easily overpower the A/C system with more than just an 80 degree result.

If you can get the heater hoses off and rig up a garden hose - the water should come out about as fast as you can put it in - very little restriction. Perhaps try running water in both directions to see if any crud comes out.

Also, are you confident that your coolant system is currently full?

Not familiar with the newer models, but other members have suggested that the A/C will kick in periodically in the 'heat' modes - a dehumidification feature.

Good luck, and keep us posted on what you find.

 

witht he heater switch on defrost, or defrost/floor the a/c will cycle to get moisture out of the air to help keep the window from fogging up.... also if you thin the a/c is the culprit... just un plug the electric plug on the compressor clutch... it wont kick on... so no cold air... then work from there... but with heat!!

 

I will have a look at the core to see if it is heating evenly - I need to flush the system.

I will report back.

Maybe the AC is only cycling and I just don't know it.... thinking that it is running all the time.

The investigation continues.....

 

The temperature difference between the 2 hoses that go though the firewall to the core is great - one HOT, one WARM.

That said, the heater hoses are a challenge all by themselves.

What is the trick to getting them off?

In Google searches I find no "heater hose removal tool" but I guess there is one out there - I see it referred to by various people but there is no real explanation of it.

Your help is appreciated.

 

Don't know what changes were made between your model year and mine. Always have seen the hoses held on by traditional hose clamps. Many times, just have to cut the hose off right at the end of the heater core tubing, then hope there's enough slack in the lines to be able to reattach. Being 11 model years old, not a bad idea just to change the hoses anyway if they're originals - be sure to leave some slack :-)

Concerned about the temperature difference - unless it was Great White North butt-cold outside, should be very little difference between the two, perhaps on the order of 20 degrees or so. An indicator that there may be a flow restriction somewhere - kinked hose, clogged core, etc.

 

Conventional hose clamps would be far too easy. The hoses snap onto the core using these special clips and the other end is attached to the water lines (leading into the block) by standard home clamps. BUT.... access to them is very difficult, hard to even SEE the clamps

 

Comming in late on this thread, heater hoses, be very carefull with them so as to not damage the core. I litterally had to cut mine off with an electricians minnie side cutters. Was doing a Preventative maintenance thing, changing all hoses. Different storie. Would remove them at the engine for the flush treatment per Wde's advice.
The AC does work in most positions, by design. Cooling system flow should have the two heater hoses and the top radiator hose nearly the same temperature by feel. The lower radiator hose should be considerably cooler.
Really like SinCity's advice to disconnect the AC plug for a random test, just love the little things like that, way to go Sin.

 

I have a 1996 F-150 and the heater button on the dash will not turn all the way to the heat it is like there is something stuck in it and the cab will not get warm. It is like a cover or flap cannot close all the way. I was wondering if this can be fixed by myself or should I get help any one know how to fix this?

 

Hodburner 54, welcome to the site. Its best to start a new thread for any questions you may have, you will get better action that way. Just like you posted to this thread there is a box for new threads right under the catagory. To answer your question, yes does sound like something is obstructing the temp dial. Hopefully an answer will be posted here to solve your problem. I would suggest either using the search button or starting a new thread as I am not experienced with this control.