Fan/blower/switch only one direction

Tiny
KARNSEM
  • MEMBER
  • 1994 DODGE CARAVAN
  • 138,123 MILES
I just replaced the heater core in my 1994 dodge caravan 3.0 base, however, regardless of the fan/switch position, the fan only blows to the windshield and side front windows. No face or foot air only windshield. I missed something but what could that be? Thanks.
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Wednesday, June 26th, 2013 AT 4:30 AM

12 Replies

Tiny
KHLOW2008
  • EXPERT
The mode doors are not working correctly. Check the vacuum lnes and ensure they are correctly and securely installed.
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Wednesday, June 26th, 2013 AT 5:58 AM
Tiny
KARNSEM
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Vacuum lines seem secured as far as I can see them around the heater box. I pulled the control from the dash, the vacuum lines there seem to be secured. What else could be the problem. Heater hose and a/c lines not connected yet, not sure if they can be related
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Wednesday, June 26th, 2013 AT 7:01 AM
Tiny
KHLOW2008
  • EXPERT
Do you have vacuum at the vacuum lines? Did you start the engine while testing the mode flow?
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Wednesday, June 26th, 2013 AT 7:06 AM
Tiny
KARNSEM
  • MEMBER
Thanks again, I am going to check right now if am getting vacuum at the lines, engine off and on. Get back to you
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Wednesday, June 26th, 2013 AT 8:16 AM
Tiny
KARNSEM
  • MEMBER
No vacuum at the vacuum lines while engine running and non-start mode, only the windshield and windows defrost vents received air while engine running and non-start mode. I pulled the control and disconnected the vacuum from the switch and test the lines, no vacuum.

Connected the lines again, still no vacuum, no vacuum at valves by the driver's gas paddle at the hvac box or at the switch nor the two line from the hvac box leading to the engine compartment.
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Wednesday, June 26th, 2013 AT 9:59 AM
Tiny
KHLOW2008
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Check vacuum at engine side. Hose could be dislodged or kinked.
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Wednesday, June 26th, 2013 AT 10:12 AM
Tiny
KARNSEM
  • MEMBER
Don't know what happened to my last post. Anyway vacuum at the engine side checked. If you're referring to the two vacuum lines from the hvac box thru the firewall by the break booster, there is no vacuum there either.

If a single vacuum line is dislodged, can it cause all this?

From where actually does the vacuum enter the hvac box, if I know that starting point, maybe I should start from there?

I just installed a/c condenser, I'm restoring the whole a/c system, hence I need to know the solution to this issue so I'll not end up doing the whole task again.
Where should I go from here? Thanks
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Wednesday, June 26th, 2013 AT 7:14 PM
Tiny
KHLOW2008
  • EXPERT
The various diagrams shows how vacuum flows in each mode. From the brake booster, there must be vacuum going to the HVAC system. If you do not have any vacuum from the brake booster, the vacuum line is either kinked or dislodged.

If any of the vacuum lines providing engine vacuum is leaking or dislodged, it would affect the others.
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Thursday, June 27th, 2013 AT 6:45 AM
Tiny
KARNSEM
  • MEMBER
Thanks for your continuous response. This's where I'm now, when I disconnected the vacuum line (black line ) coming from the HVAC system to the Blake booster connecter, (vacuum check valve?), With a finger placed over the booster hose, my finger get sucked -in by the Blake booster side, but not from HVAC line side.

You said "From the brake booster, there must be vacuum going to the HVAC system.
Why then the blake booster line is sucking air inside the booster but not pushing air/vacuum to the HVAC system? Is the blake booster suppose to work like that?
If it's designed to work like that, then there is vacuum there at blake booster?

Could this issue be also some kind of electrical, perhaps the heater---A/C control switch, since the cigarette lighter also has stop working?
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Thursday, June 27th, 2013 AT 8:00 AM
Tiny
KHLOW2008
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The brake booster works on vacuum and the HVAC system piggy backs on the system. You need to check the hose leading from booster to HVAC system. There is a checkvave in betyween, ensure it has not been reversedly installed, which would result in a no vacuum situation.
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Thursday, June 27th, 2013 AT 8:16 AM
Tiny
KARNSEM
  • MEMBER
Success, it was exactly as you said, the check valve was reversely installed. Corrected it and all is good. Thanks. Please send link so I can increase my donation a bit.
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Friday, June 28th, 2013 AT 4:04 AM
Tiny
KHLOW2008
  • EXPERT
Glad to know you have solved the problem.

I am not sure about additional donations but if you go to your initial post, I believe at bottom of the question you have an upgrade question link. Click on it and it should bring you to the donation page.

Thanks for the donation.

Have a great weekend.
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Friday, June 28th, 2013 AT 6:21 AM

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