Best Answer
AC blowing through defrosterI think I can point you in the right direction. On my van, this happens when the engine is under a load (such as accelerating) and vacuum drops. It returns to the vents when desired speed is reached and vacuum returns.

However, this problem occured with my van at all times and it turned out to be a vacuum leak. I had a broken line that went to the vacuum motor controlling the blend door for the ventillation system.

There are some vacuum lines that come through the firewall, from inside, and go to vacuum ports on the intake manifold. Follow these lines back to the motor and inspect for breaks or holes. If you are unable to find one, make sure the engine is warm, running, and AC blowing out the defrosters, and spray something flammable like penetrating oil (I've always used CRC brand but any will work) on the lines, connectors, and even where the intake manifold is bolted to the cylinder heads. When you find the vacuum leak, engine idle speed will increase. If that is not successful, you may want to check the vacuum lines under the dashboard. Your problem is definitely vacuum related and is probably near the motor because it seems to happen after the engine warms up.

Hope this helps!Mark

User Avatar

Wiki User

βˆ™ 2011-09-13 22:24:51
This answer is:
User Avatar
Study guides

Add your answer:

Earn +20 pts
Q: What causes the AC on a 1999 Dodge 1500 Conversion Van to work great until you drive it for a while and then it stops blowing from the dash vents and blows from the defroster vents?
Write your answer...
Still have questions?
magnify glass
Related questions

Why doesn't my dodge w250 defroster work?

One reasons a Dodge W 250 defroster may not work is the blower motor relay. This can be replaced easily. If it isn't the relay, there may be a problem in defroster door binding. A mechanic will be able to determine the cause.

Fuel pump fuse keeps on blowing on a 1999 dodge neon what are the possible causes?

most likely a faulty fuel pump.

Why won't our 2001 dodge ram 1500 conversion van defroster keep the whole windshield and front door windows clear?

Because Dodge doesn't use a full dashboard grill like Ford and Chevy. A few holes in the dashboard doesn't cut it. Same with mine.

My 1999 Dodge Ram only blows air at the feet not at the defroster or the dash How do I fix this?

The vacuum line that goes to the defroster is probably disconnected, possibly on the fire wall.

01 dodge durango Rear window defroster light keeps flashing all the time and ac does not work?

rear window defroster light keeps flashing

What would cause all power windows to only work once in awhile and defroster to go out on 2004 dodge ram?

what would cause all power windows to only work once in awhile and defroster to go out on a 1997 dodge intrepid

What is an ebl relay?

EBL is an abbreviation for electronic back light That is what Dodge calls the rear window defroster.

Why does my 2001 dodge air conditioning not blow cold?

if its blowing, but not blowing cold its low on coolant. it takes r134a.

Why might the defroster-heater not be working on a 1997 Dodge Ram pickup?

If the air is blowing but not hot, you may be drawing in too much cold air while driving down the road. If that is the case, try blocking off a portion of your radiator with a cardboard box. Do not block all of it off as your vehicle may overheat. You might need to have the heater core flushed if its not blowing out hot air. If it its not blowing out anything try replacing the blower motor.

How to fix rear window defroster button on 1996 dodge neon?

replace it, it should just pop out of the console

Dodge Ram 2500 conversion van what does it means?

This is a Dodge Ram 2500 Van that was converted.

Where can you buy or fix your dodge conversion van?

depending on what is wrong with it and what type of conversion ist camping or touring

People also asked