A/C blows from dash to defrost when accelerating

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Sep 27, 2000 | 07:57 AM

murrman

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A/C blows from dash to defrost when accelerating

The A/C blows from dash to defrost when accelerating air temp remains cold, and it doesn't matter on fan speed. Think it's a vacuum prob, but not sure where to start!

Mark
'93 F-150 XLT, 5.9L, 4x2, A/T, Factory A/C

Sep 27, 2000 | 10:29 PM

nitro94

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From: Wichita USA

A/C blows from dash to defrost when accelerating

This system will have a vacuum line coming off the intake going towards the firewall and thru to the control panel with a vacuum reservoir connected inline. Will sometimes tee off and also supply vacuum for cruise. You will usually find the problem under the hood in these lines. Is possible that break could be under dash where they route thru to the panel or a bad panel vac. switch or leaking vacuum door motor.

Sep 29, 2000 | 11:03 AM

murrman

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A/C blows from dash to defrost when accelerating

Cool... I'll check it out.

Thanks

Sep 30, 2000 | 01:13 PM

tominator

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From: New Baden, IL. USA!

A/C blows from dash to defrost when accelerating

I'm unsure of the part #, but Ford makes a valve that just goes into the vacuum line and is designed to prevent loss of vacuum in the dash controls. It is not model specific.
Check with your dealer. A sharp parts man will know what you're asking for.

Dec 19, 2000 | 03:34 PM

fordiesel69

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From: Erie, PA

A/C blows from dash to defrost when accelerating

I had the same problem with my 85 Grand Marquis. It was a broken vac line under the dash. I fixed it once and it did it again next year. I decided to live with it. Have fun finding the broken line!!!!