Another A/C blowing out defrost question
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Joined: Jul 2012
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Another A/C blowing out defrost question
I bought a 2003 f150 lariat 5.4 in February of this year, it has the climate control a/c. I noticed at the start of summer when I turned the a/c down to a lower temperature that the air would come out of the defrost vents. their really is no certain temperature at which it does it, it seems to depend on what the truck thermometer says the outside temperature is. I now have to start the temp at 85 and work it down slowly from there. It is getting to be a problem now that the outside temp is about 100. The air will still come out of the defrost even when set at 85 because it is so hot outside. I also hear a whistling sound that seems to be coming from the passenger side dash. I assume its a leak but I know nothing about the vacuum system or where to start looking. any and all help is appreciated. Thanks.
Here's an example to help you understand how its working.
Say the truck says its 101 outside, I set the temp to 85 and it blows out the defrost. When the temp hits 85 inside it will start coming out of the dash like normal, I can then bump the thermostat down a few more degrees to make it blow harder but if I move it down too much it will start blowing out of the defrost again. I repeat this process over and over until it is a comfortable temp.
Here's an example to help you understand how its working.
Say the truck says its 101 outside, I set the temp to 85 and it blows out the defrost. When the temp hits 85 inside it will start coming out of the dash like normal, I can then bump the thermostat down a few more degrees to make it blow harder but if I move it down too much it will start blowing out of the defrost again. I repeat this process over and over until it is a comfortable temp.
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Joined: Dec 2011
Posts: 12
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From: Southern NJ
See my self response post below yours
you do have a vac leak that is probably showing itself with the rise in temperature. there is a 3 way check valve on a vac line that is right under or behind your computer. it goes into the firewal via a rubber grommet. there is another gray / white vac line coming out and going to the vac valve that controls hot water flow into the heater. the black line coming out of the grommet goes to a check valve that is actually daisy chained off the 3-way check valve. take a look at the single check valve and black tubing. you can get a new check valve for $4 from Advanced auto on the vac supply rack. you can also get new tubing and some rubber fittings.
it would only take 15 min to replace all of that and I'll bet you problem will be solved.
Good luck.
it would only take 15 min to replace all of that and I'll bet you problem will be solved.
Good luck.
