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Jerry
Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 1754
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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Dodge ran van: I have a 1999 ram van 2500, my ac/heat only

Customer Question

I have a 1999 ram van 2500, my ac/heat only blows through the defrost vents
I replaced the control mod already
Submitted: 1 year ago.
Category: Dodge
Expert:  bill replied 1 year ago.
THIS IS an indication there is no VACUUM getting to the control head have you checked the lines from the engine to the head there is a BLACK line off the intake manifold that runs to the RIGHT fender to a black ball (it's buried under the right front fender extension so you may need to dig for it then to the control head any loss of the vacuum signal will result in only a defrost.
Customer: replied 1 year ago.
yes there is vacuum at the black ball
next?
Expert:  bill replied 1 year ago.
I do not understand your answer should I assume you FOUND the black ball in the fender and have vacuum at it?do you have vacuum AT THE CONTROL HEAD?
Customer: replied 1 year ago.
yes I found the black ball and I have vacuum at it, I have not checked the control head yet, which should I check, the one with 2 lines or the other
Expert:  bill replied 1 year ago.
the vacuum feed line should be BLACK and runs through the firewall that's the line to check it should run directly to the control head, exactly where and how will depend on how the van was originally built remember many of these were upfitted after being built and just as many were base models so you will need to follow the line to the connection
Customer: replied 1 year ago.
ok, I will look tomorrow, is there a diagram I can refer to?
I'm a carpenter, I can build a kitchen from a pile of wood but mechanics or not my strong suit
Expert:  bill replied 1 year ago.
we never has any diagrams for the older vacuum systems the system is very simple and relies only on engine vacuum, so if there is no vacuum at the control head then simply follow the line that passes through the firewall to the black ball, the ball is a reservoir for holding vacuum it comes into play when you accelerate and the engine vacuum drops low this tank holds enough vacuum to keep the doors where they are set and not defaulting to defrost, when there is no vacuum at the control head the system defaults to defrost, like a well water house it has to have a holding tank to provide a constant pressure.so lets assume there is NO vacuum to the head follow the outlet line from the ball to the dash looking for ANY cracks in the line especially around the battery and around the cruise control this also works on the engine's vacuum if you do NOT have speed control there will still be a "T" in the line and should be a cap over it look over this line very closely as any breaks will cause the system to become inoperative.
Customer: replied 1 year ago.
Ok , I will check all of that. Thank you
Expert:  bill replied 1 year ago.
no problem let me know what you find
Customer: replied 1 year ago.
I will
Expert:  bill replied 1 year ago.
checking in to see if you made any progress
Customer: replied 1 year ago.
I just got home from work, My son is going to work on it this weekend will I'm away. I told him about the vacuum line, he works at a body shop so they should be able to get it fixed. I will update you on Monday
Expert:  bill replied 1 year ago.
ok I look forward to hearing the results