AC blows cold then hot upon acceleration and

Tiny
KARIM ALEEM
  • MEMBER
  • 2000 DODGE RAM
  • V8
  • 2WD
  • AUTOMATIC
  • 211,000 MILES
When I turn on the AC it blows very cold. The problem comes when I drive for about ten minutes, if I accelerate or just driving along it begins to blow hot air. The hot air is preceded by the sound of a closing vent flap. The coolant level is within normal limits.
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Thursday, April 16th, 2009 AT 5:35 PM

23 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
This sounds like the temperature blend door actuator needs to be replaced. Here is a guide that will show you step buy step how to do the job and with diagrams below to show the location for your car:

https://www.2carpros.com/articles/replace-blend-door-motor

Check out the diagrams (below). Please let us know what happens.

Cheers
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Saturday, April 18th, 2009 AT 9:09 PM
Tiny
KENDRARUSSELL
  • MEMBER
Thank you this guide helps me fix my truck for $56.00 I love this site.
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Monday, August 6th, 2018 AT 4:09 PM
Tiny
2CARPROS-ARCHIVES
  • MEMBER
  • 1999 DODGE RAM
  • 160,000 MILES
My 1999 Dodge Ram 1500 5.2L always blows hot air, the clutch on the A/C compressor kicks on and off even when the switch inside is turned off and on heat. When A/C is turned on it blows hot. When you turn off everything. It will blow hot air out the front vents off and on and off
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
KEN
  • ADMIN
Hello,

It sounds like you have a temperature blend door actuator that is out. Here is a guide to show you what you are in for when doing the job:

https://www.2carpros.com/articles/replace-blend-door-motor

Here is where the location of the temperature blend door actuator is on your car (below).

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
THEWELDER
  • MEMBER
  • 1999 DODGE RAM
  • V8
  • 4WD
  • AUTOMATIC
  • 74,000 MILES
I have a 1999 dodge ram 1500 sport, 318 auto 4 x 4. AC works great when first turned on, then when traveling it instantly goes to hot air, and just as quickly turns back to cold. Good for several miles, then same problem again. AC Pressures were checked and are in range, also freon level is good. Driving me crazy! Please steer me in the right direction. Thank you
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
1999 Dodge Ram AC goes from cold to hot, then back to cold

An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.

For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that is contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.

Some refrigerant identifier equipment can detect air in the system as well as other contaminants. An identifier should be used to check the refrigerant before the system is serviced to prevent cross-contamination of recovery and recycling equipment.

Possible causes of intermittent cooling in a manual A/C system that might be caused by an electrical problem include:

Faulty low pressure cutout switch. This switch prevents the compressor from running if the refrigerant level is low. If the cutout switch is not reading correctly, it can prevent the compressor from coming on.

Faulty compressor clutch. The magnetic clutch on the compressor requires full battery voltage to engage. If the voltage to the clutch is low, or the clutch coils have too much resistance, or the air gap in the clutch is too great, the clutch may not engage to drive the compressor.

Faulty compressor clutch relay. Check to see if the relay is receiving voltage when the A/C is turned on. Also check the relay wiring and ground connections. If bypassing the relay with a jumper wire or routing battery voltage directly to the compressor clutch makes the A/C work, the relay is probably bad.

Faulty A/C control switch. The switch may be worn and not making good contact when it is turned on.

Some possible causes of intermittent cooling (or no cooling) on automatic A/C systems include all of the above, plus:

A problem in the control module or control head (this usually requires using a dealer scan tool to read fault codes and perform self-diagnostics).

A bad temperature sensor (an ambient air temperature sensor, interior air temperature sensor, evaporator temperature sensor, or sunload sensor). Again, a factory scan tool is usually required to perform diagnostics on the system
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
KOKOANDFIN
  • MEMBER
  • 2001 DODGE RAM
Air Conditioning problem
2001 Dodge Ram 6 cyl Two Wheel Drive Automatic 200.00 miles

The air blows cold until we have to stop, it then blows warm air. Why?
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Its probably freezing up due to air and moisture forming ice and blocking off the orifice tube/expansion valve, might want to have vacuumed out-
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
TTBONE64
  • MEMBER
  • 2001 DODGE RAM
  • V8
  • 2WD
  • AUTOMATIC
  • 99,500 MILES
I don't know a lot about auto A/C. But the old ladies truck is a 2001 dodge ram 1500 v8 automatic. When the problem started it would blow hot for a few min. Then cold for a few and back and fourth. Now if you go to the corner store it will blow cold on the way there but hot on the way back. After it sits for a few hours it will blow cold again. PLEASE can someone help?
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
When it blows hot air, is the AC compressor working?
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
TTBONE64
  • MEMBER
NO
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
I need you to check to see if power is getting to the AC clutch when it doesn't work. Just use a test light.
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
TIGERT39
  • MEMBER
  • 1998 DODGE RAM
  • 126,981 MILES
Air conditioner comes on blows strong and after the engine warms up the air blows low. If it is hot outside and all the Windows are up the air does not come on at all and if it is cool or on a rainy day the air comes on and blows cold. I checkd the freon and they said it was fine. The fan is on and everything and thd heater does not work.
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
HMAC300
  • EXPERT
Check fuses and relay I've pointed to in pic also check ground and connection.
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
SCOTTO
  • MEMBER
  • 2001 DODGE RAM
  • 79,500 MILES
My Dodge ram 1500 on the freeway the AC runs great when I get off the freeway I hear something close and hot air comes out what is going on it does it when the truck is in park the AC runs great but when I drive the truck on city streets it will blow cold air for 2-4 min and same thing something closes ant hot air comes out please help
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Suspect fault in blend door actuator an motor controled by temp switch. Closes a door to close off heater core and let all air flow through evaporator. The noise you hear is door so switch maybe at fault or actuator motor. Operate TEMP switch from hot to cold does it respond and change vent temp?
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
SCOTTO
  • MEMBER
Ware is the blend door actuator mirror on my 2001 Dodge ram 1500?
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
SCOTTO
  • MEMBER
Ware is the blend door actuator mortor on my 2001 Dodge ram
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Bummer is instrument panel needs to come out the HVAC unit
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Monday, August 6th, 2018 AT 4:11 PM (Merged)
Tiny
COLTE
  • MEMBER
  • 1999 DODGE RAM
  • V8
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
AC works when turned on, then in about 5 minutes, starts blowing hot air. You can hear what sounds like a damper shutting when it starts blowing hot air.
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Monday, August 6th, 2018 AT 4:11 PM (Merged)

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