A/C wont turn off
10-26-2011, 08:59 PM
#1
Junior Member
Thread Starter
Join Date: Oct 2011
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
A/C wont turn off
Sooo i have a 1999 f150. since i finally got freon on for my truck the heat will not turn on. i can turn the knobe all the way to heat but i can hear the ac turn on, the engine revs to compensate for the extra power and cold air comes out. So does anyone know the fix for this or a temporary fix cuz i live in Michigan and its cold already. id rather not work outside in the cold.
10-26-2011, 09:45 PM
#2
The compressor should only run in AC, Max AC or either defrost setting. If you're on regular vent and the compressor is running you've got a problem. Also, even with the ac running if the temp is turned to heat the air coming out should be hot. If it's cold you either have a blend door problem or a plugged heater core/low coolant.
First obviously check your coolant. If it's good let your truck warm up and put the heat on. After a minute feel the two smaller black coolant hoses leading to the heater core, they're going into the firewall on the passenger side of the truck.
If one is warm and one is cold you have a plugged heater core. You can try unhooking both hoses, leaving them attached to the heater core and trying to flush it out with a garden hose, putting pressure to one side then the other to break rust and crap loose and hopefully freeing up the passage and possibly getting you through the winter. You might have to replace it though if you can't get it unplugged.
If both of them are hot, your heater core is good and you've got a blend door problem. If you hear a steady click click click from under the dash it's a bad actuator, that's the only give away solution though. If it's not that you need to figure out if the actuator is moving or not. It's in the dash in the middle and a PITA to get to. You'll have to find a manual or something to show you because I can't really describe it. If it is moving there's a physical problem with the blend door and you need an air box and if it's not moving it's either a bad actuator or switch or wiring.
To test that you need to make sure the actuator is getting power on the light blue/pink wire and ground on the black wire. Just use a voltmeter set to ohms between the black wire and a good ground to test continuity.
Then test the resistance between these pins for continuity:
control switch Pin 3 actuator Pin 4 436 (R/LG)
control switch Pin 2 actuator Pin 3 437 (Y/LG)
control switch Pin 1 actuator Pin 6 438 (R/W)
If they all ohm out put the meter between yellow/light green and red/light green at the control switch and set to warm ohms should be over 3,000 and full cool under 300. Also make sure it sweeps fairly consistently between 300 and 3,000.
If all the wiring/switch checks out replace the actuator.
Or replace the control switch cause it's easier then if it still doesn't work replace the actuator then if it still doesn't work you know it was the air box or some wiring. That's called throwing parts, sometimes it works out but 99% of the time it costs a lot more and takes longer.
First obviously check your coolant. If it's good let your truck warm up and put the heat on. After a minute feel the two smaller black coolant hoses leading to the heater core, they're going into the firewall on the passenger side of the truck.
If one is warm and one is cold you have a plugged heater core. You can try unhooking both hoses, leaving them attached to the heater core and trying to flush it out with a garden hose, putting pressure to one side then the other to break rust and crap loose and hopefully freeing up the passage and possibly getting you through the winter. You might have to replace it though if you can't get it unplugged.
If both of them are hot, your heater core is good and you've got a blend door problem. If you hear a steady click click click from under the dash it's a bad actuator, that's the only give away solution though. If it's not that you need to figure out if the actuator is moving or not. It's in the dash in the middle and a PITA to get to. You'll have to find a manual or something to show you because I can't really describe it. If it is moving there's a physical problem with the blend door and you need an air box and if it's not moving it's either a bad actuator or switch or wiring.
To test that you need to make sure the actuator is getting power on the light blue/pink wire and ground on the black wire. Just use a voltmeter set to ohms between the black wire and a good ground to test continuity.
Then test the resistance between these pins for continuity:
control switch Pin 3 actuator Pin 4 436 (R/LG)
control switch Pin 2 actuator Pin 3 437 (Y/LG)
control switch Pin 1 actuator Pin 6 438 (R/W)
If they all ohm out put the meter between yellow/light green and red/light green at the control switch and set to warm ohms should be over 3,000 and full cool under 300. Also make sure it sweeps fairly consistently between 300 and 3,000.
If all the wiring/switch checks out replace the actuator.
Or replace the control switch cause it's easier then if it still doesn't work replace the actuator then if it still doesn't work you know it was the air box or some wiring. That's called throwing parts, sometimes it works out but 99% of the time it costs a lot more and takes longer.
