ReneB64

Hey all, seems like my truck has been giving me problem after problem recently. Noticed one cold day in cab, near passenger side glove box i heard a couple seconds long high pitch screeching noise. Like a cap burning up or something. My heater stopped working, since it was temp control i replaced the temp control blend door. Seemed to make a difference but heat is intermittent. Any ideas? I have to imagine that noise was something burning up. No burnt smell, blows hard, ac works fine. But call for heat blows cold. It is auto climate control.

techrep

iTrader: (1)

Blend door stuck or fouled with foam, motor may of burnt up on you. double check your heater hoses under the hood at operating temperature to ensure they are hot.

ProjectSHO89

Any time there is a "no heat" situation, ALWAYS start under the hood and see if you have HOT coolant flowing through the heater core. If you do not have that, you will NEVER have heat in the cabin regardless of what is going on under and in the dash.

Once that is established, you can move on to the controls in the dash.

ReneB64

I already replaced the blend door. I was able to hear door moving, not sure I hear it any more. Have to take a look again to see if shaft is turning.
After that, i was thinking about checking heater hoses like you mention.
The controls all seem to be working and air comes out of the correct vents, its just that is blowing cold and heat, only intermittently.

Another note, I had a mechanic work on my truck (oh no), and I noticed the AC was not cooling. The static pressure was pegged, greater than 90, and the AC was blowing warm air. I put an old empty can of refrigerant, and bled it a bit, the static pressure dropped a bit, maybe still a bit high based on outdoor temperature and the AC started to blow colder. I also noticed when the compressor is cycling about every 10 seconds, the low side pressure drops significantly, and then goes back up when the compressor shuts off. Isnt the low side pressure supposed to be stable?
Thanks

ProjectSHO89

Completely normal if the ambient was over 80F.
Relatively so but it depends on variables. Should stay or vary between about 25 and 45 psi depending on the load on the system. Yours probably was okay until you dorked around with it and made it so that it's now undercharged.

You should have first determined why the clutch wasn't engaging.

laterongc

why is the free and easiest step not being addressed….. checking heater hoses?

ReneB64

Thanks for your constructive feedback. The clutch is engaging; but as it shuts on and off It is cycling between about 25 and 45; it blows cool now when it did not before. My question was, shouldn't it be stable? It was not stable when it may have been over pressurized (was 70 degrees outside, chart said should be 70 psi and it was pegged, over 90 psi). I read that the pressure cycles largely when it is low but can also when it is over pressurized.

On another note, I verified both the temperature blend door actuator and vent actuator are both turning when called. It looks like the reason that I may not have heat is that it came back from mechanic, and the antifreeze was low. They had to drain the coolant, and evacuate the ac because they replaced the phasers. Seems like not attention to detail anymore, all over the place. Thanks for the tip, Laterongc, the hose was cold, then I noticed the antifreeze was low.

ProjectSHO89

Good, sounds like you're well on the way to solving that issue.

It likely would have if you hadn't removed refrigerant from the system making it undercharged now. Undercharged systems tend to short-cycle the compressor clutch, assuming the system is otherwise working correctly. As I already noted, static pressure when the compressor is not operating is SUPPOSED to be high. Roughly 1.1 to 1.2 times the temp in degrees F is a good rule of thumb.

needsmoarturbo

I would concur that now the charge is too low, when the pressure drops below 25 psi the compressor shuts off, then when it rises above 40 ish it comes back on again, and there you have your cycle. If it's properly charged and the compressor is working as it should the low side will sit at a fairly solid 30-40 psi when you have the system running steady state depending on ambient. I would concur that 90 psi seems like a totally reasonable static pressure depending on ambient temperature it can even go up from there on hot summer days, like up to 105psi from my observations.

ReneB64

Just to wrap up after my 2008 F150 FX4 returned from the mechanic The air conditioning I was not blowing cold and heater not blowing hot.. They had replaced the phasers and seems like did not fill up the coolant and also did not fully charge AC. Symptoms were that the heater was not working and AC was not blowing cold The pressure was cycling when I looked at it and was low thanks for everyone's input