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sprinkles08, Chrysler/Dodge/Jeep master tech
Category: Dodge
Satisfied Customers: 23117
Experience:  ASE Master and Advanced Certified, Chrysler/Dodge/Jeep Master Certified, Trans and Hybrid Specialist
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1999 ram 1500 replaced the ac check valve above the

Customer Question

1999 ram 1500 replaced the ac check valve above the evaporator still have the same problem with the ac when I come to a stop some times the ac will blow ambient air for about 15 sec. then it will go back to normal. when on the freeway and going up hill
the ac will not blow cold air until the top of the hill also the cruise control slowly decrease from it original setting the bigger the hill the more apparent the condition is.
Submitted: 2 years ago.
Category: Dodge
Expert:  sprinkles08 replied 2 years ago.
Hello and welcome to JustAnswer!
A vacuum issue won't affect temperature but most likely what you're experiencing is the mode switching to defrost. When vacuum to the defrost actuator drops off then it will default to blowing from the defrost. It isn't' uncommon for these to switch to defrost on acceleration due to the loss of manifold vacuum.
There is another check valve at the elbow where the vacuum hose comes off the intake. Make sure this one only flows in one direction or replace it.
Also make sure all hoses are intact and connected including the cruise servo, brake booster, and purge hose.
The vacuum reservoir is in the right side of the wiper cowl. Make sure the reservoir is plumbed into the system and isn't leaking.
I've seen cases were low engine vacuum caused this, often due to a leaking plenum pan gasket on the bottom of the intake.
Customer: replied 2 years ago.
I will check the vac. reservoir tomorrow and get back with you check the other areas didn't see any problems wasn't sure where the purge hose was.
Expert:  sprinkles08 replied 2 years ago.
The purge hose goes from the intake to the purge solenoid in the right front of the engine compartment.
Customer: replied 2 years ago.
Check the vac. reserver no loose of vac. will check the purge hose solenoid and git back with you next week I am out of town its the reason I did not get back with you after your first response back in June/ July I rated you any way but still had the the problem.
Expert:  sprinkles08 replied 2 years ago.
This question from three days ago has not yet been rated.
Let me know if you need any more help.
Customer: replied 2 years ago.
been out of town the reason I haven't got back with you; used the truck the other day and had just the fan blowing air at my face (ac off heater off) and came to a stop and heat started coming out of the vent, not outside ambiant air temp. but heat, in my face, the control was set at cold. When it happens with the ac on I have to turn the ac off for about five second and it will blow cool again if I turn off the ac and turn it back on too quickly it will still blow hot air. Also had a P0455 evap. code. Checked for leaks and cracked hose didn't find any replaced the gas cap and cleared the code been driving around to see if the code will come back. can I check the intake system without change the gasket by spraying carb. cleaner around to se if change in engine rpm. Have a scan tool it is only capable of reading live data would that help me to find out if I have a leak at the plenum?
Expert:  sprinkles08 replied 2 years ago.
If it's blowing from the correct location but the temperature is changing then you have a blend door issue. The blend door is cable driven, the cable running from the control head to the top of the heater box. If you're able to control temperature but it's changing on it's own then most likely the cable has popped out of it's holder on the heater box and is moving somewhat freely. You can remove the control head and see if there is an issue with it or the cable there, if not then the dash would need to be removed to access the cable at the heater box.