Have a 1999 F150, V6, 5 speed. Just purchased recently. The problem with the heat or air is it is either full hot or full cold and can't control the temp at any time. Where do I start? Replace the climate control or just *****? Please help!

 

Check for a busted temperature blend door.

 

I'm having a similar issue. When I first got my 99 the AC would kick to heat without even turning the ****. I hired a buddy to replace the blend door and that issue went away but a new issue was introduced. The **** that controls the temp (blue to red) now has a weird tension on it. As you turn it you can feel the tension tighten and release.

The real issue is the fact that it is either very hot or very cold. There is no in between now. I read other posts that said to replace the blend door but that has already been done in my case. Any suggestions?

 

Check for a stripped TEMP ****.

 

Thank you. I removed the **** and it appears fine. I took a pair of needle-nose pliers and turned the white shaft manually. Right in the middle it switches from blowing very hot to very cold. There is no warm. Any other suggestions?

 

Probably time to break out the ohmmeter and check the TEMP potentiometer. Do you have a meter?

 

No, but I'll see if my buddy can do it. What would we check exactly? Thank you for your help, BTW.

 

What year truck do we have here ??

 

It is a 99

 

OK...I saw the 2007 in your sig and got confused. If it was the new body style chances are the problem would be the blend door actuator motor..common problem with those. Not sure with the 99...sorry.

 

Yeah, we replaced the actuator at the same time I'm pretty sure.

 

1st time I needed heat was 12/2/2012, badly needed the defroster. Only cold air, but working the climate control gave signs that the system might just come around to normal. That was only momentarily, and on a round trip of 1300 or miles I was without heat and badly needed the defroster.

I ordered a 1999 F-150 shop manual for $14.99 from the Internet. First, by removing the valance panel on the floor over the hump I performed a systematic test on the climate control, which goes from full cool to full warm anticipating the given specs of 300 ohms (or less) to 3000 ohms (or greater), respectively, and increases/decreases linearly in between, controlled by a potentiometer. This check was right on the money. This test requires the removal of the valance panel on the floor just above the "hump." The 3 wire lead from the climate control (cc) **** goes directly to the blend door actuator, which is sandwiched between the plenum and the floor duct, but is easily unplugged for testing. One of the tests in the procedure led me to believe the blend door actuator was bad - tests for a short between one of the pins and ground and the manual instructed to replace the actuator. (It turns out the actuator was not bad and I must have had made a mistake in this part of the test.)

To take the actuator out: (1) remove a small brace just to the right of the actuator, which is bolted to the floor up to the assembly (easy), over to the left side is another brace, which the instruction says to loosen at bottom and swing out of the way, although I loosened but it would not move - I let it be, (2) remove the RCM (Restraints Control Module), which are bolted down with three bolts. The RCM is between the floor duct and the floor. This was easy and I left it unplugged. I made sure at all times the negative ground cable was removed from the battery. (3) Last, but sure as Hell not easy are two #8 screws (may be metric, but they're close enough an SAE 8) when removed allows the floor duct to be pulled out and hence access to the three screws used to attach the actuator to the bottom of the plenum. One is on the right hand side easily found and not too hard to remove. The second one is almost impossible to access, definitely not visible, because it is on the backside to the right just a tad from the vacuum motor. I used a small 5/16 box wrench (an 8 mm, which is .006" within 8mm, is probably the actual size, a small ratchet or a small socket driver can't get to it. I made a small socket driver that I could finger turn if I ever broke it loose. I may have spent several days getting this booger out (I'm retired.) Finally, I was left with pulling out the floor duct (this is not easy either twisting here then there and a few Hail Mary's. The three screws used to secure the actuator are fairly easily removed.

When I separated the actuator from the bottom of the plenum a couple pieces of black plastic fell out, which is the bottom part of the blend door, which was obviously my problem!!

I had already bought a new actuator from Advanced Auto parts for $41.15. I plugged the lead from the cc **** into the removed actuator, carefully reconnected the battery ground cable (remembering the RCM,) ignition on and operated the cc **** thru the full range of about 75 degrees more or less; it verified my old actuator was good. I did the same test with the new one to see if speed of movement, and range was the same, which it was.

I can conclude the removal and testing of the actuator was fairly straightforward with the exception of that one screw. Replacing the blend door inside the plenum looks like the F150 nightmare from Hell. Ford Motor Company should be held accountable and have to pay due to using such a flimsy part in such a location. A very trustworthy mechanic talks of $400; I think this will be far below Ford Service.

 

OMG my local Ford Dealer just gave me a quote to replace the blend door - $985. This is all due to Ford using a sub-quality component made of sub-quality plastic in an almost inaccessible area. This is almost like using a piece of pot metal in the heart of an Abrams tank.

 

Update: I installed a new control unit (switches) and the weird tension is gone with the temp control ****. However, I still have the issue of just hot or cold. There is no warm or cool. What do you suggest I have the guy check who replaced the blend door?

 

That is a puzzle in that you get the max cold or max hot with no change in between with the temperature control switch. This switch is a potentiometer, at full warm (hot) about 3000 ohms should be measured and at full cool (cold) it should be about 300 ohms. It varies linearly in between. This controls the blend door actuator; it's shaft moves thru a rotation of about 90 degrees. For example, at full cold 0 degrees (300 ohms) , about 1/2 toward hot about 1650 ohms, about 3/4 toward hot about 2025 ohms and full toward hot about 3000 ohms. You can see this actuator by removing the valance panel located over the hump just below the A/C Heater controls. The actuator is sandwiched between the floor duct (on the floor) and the plenum up and behind the dash. It’s has a lead (wires), which plugs into the actuator. If you take a flashlight and look between the (narrow) space between actuator and plenum on the right-hand side about 2” back you should be able to see the shaft, which had a diameter about 3/8”. Turn ignition on and rotate from full cold to full hot (the shaft turns very slowly.) It turned out my actuator was good, but the bottom part of the blend door inside the plenum had broken. Prior to my testing it began to work sporadically and weirdly (only hot when I wanted A/C or vice versa.) Finally, forever COLD. Bad actuators are not too bad to replace and the part itself costs about $40-50. The blend door is very labor extensive and my local Ford dealer quoted $985. It turned out I got my problem fixed (new blend door) from a trustworthy and honest mechanic for $465. I do have a diagnostic diagram, which might be helpful.