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Dave Nova
Dave Nova, ASE Certified Tech
Category: Car
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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What is wrong with my heating system when it only blows out

Customer Question

what is wrong with my heating system when it only blows out the defroster?
Submitted: 5 years ago.
Category: Car
Expert:  Dave Nova replied 5 years ago.
Hello and thank you for trusting me with your question. The problem you are having is a common one. The mode controls (vent, floor, defrost) are vacuum controlled. Normally the problem is caused by a deteriorated or broken vacuum hose. This hose comes off the drivers side of the engine and runs across to the passenger side T fitting. See picture below. Vacuum line is the one shown with a dashed line.


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Thank you,
Customer: replied 5 years ago.
Thanks for the info...BUT thats not it.The vaccuum line is intact.any other solutions?
Expert:  Dave Nova replied 5 years ago.
With engine running, move the controls in the van, do you hear any suction at the controls or behind the passenger side of the dash?
Customer: replied 5 years ago.
nothing at all,just stays on the defrost setting
Expert:  Dave Nova replied 5 years ago.
Check the option code label in the glove box. Do you have option code C42, C60, or C68?
Customer: replied 5 years ago.
no numbers in the box at all.i think its time to give up here...thanks for trying but I think I need my 29 dollars back
Expert:  Dave Nova replied 5 years ago.
You can click the Help link at the bottom of the page to process your refund.