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Heat/AC control stuck 7 years 5 months ago #1621

  • billfrank38
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I used the Defrost setting, (selector in the last position to the right) last weekend, and the lever is now stuck in the Up and Down position and will not return to the positions to the left. The AC compressor is not running in this position.

How does one remove enough of the covers from the dash area to access this control? Any diagrams or service instructions on this problem?

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Heat/AC control stuck 7 years 5 months ago #1625

  • gdill3
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I used the Defrost setting, (selector in the last position to the right) last weekend, and the lever is now stuck in the Up and Down position and will not return to the positions to the left. The AC compressor is not running in this position.

How does one remove enough of the covers from the dash area to access this control? Any diagrams or service instructions on this problem?


Welcome to the Forum, Bill.

Below is a link with a brazzilion answers to 700/900 problems including HVAC repair.

If you Volvo has airbag(s) be sure to disconnect the battery negative cable (get radio code fist!) before breaking into the dash.

If you don't find details of dash removal just holler and we'll go ogle up some pics.

George Dill

www.swedishbricks.net/700900FAQ/FAQSummary1.html
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Heat/AC control stuck 7 years 5 months ago #1627

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I will have a go at it tomorrow morning.

Thanks.

Bill

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Heat/AC control stuck 7 years 5 months ago #1630

  • billfrank38
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I finally got around to removing the panel and exposing the HVAC control. Photo attached. As may be seen, the selector is on the windshield/floor position. It will move to the right for Full Defrost, but will not move any further to the left. Tried jiggling the moving parts attache to the lever while attempting to move it left, but no success.

Can anyone advise me on this problem?

Thanks,

Bill
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Heat/AC control stuck 7 years 5 months ago #1631

  • gdill3
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I finally got around to removing the panel and exposing the HVAC control. Photo attached. As may be seen, the selector is on the windshield/floor position. It will move to the right for Full Defrost, but will not move any further to the left. Tried jiggling the moving parts attache to the lever while attempting to move it left, but no success.

Can anyone advise me on this problem?

Thanks,

Bill


Yup, but you may wish to ignore my advice.

Firstly, be sure to have alternate transportation before clicking on this...

www.volvoclub.org.uk/faq/HeaterCoreReplacement.htm

...and scrolling to the end for the heater unit diagram that matches your model 740.

As you can see the lever that won't move is connected via cable to a housing with internal baffles which divide the air according to the lever's position. This physical connection is just one of the control mechanisms that move things behind the dash - vacuum and spring tension are two others.

The balky lever could be caused by a mechanical component failure, a disconnected fastener or even a collection of debris in the moving parts.

If you plan to keep this car long-term (YES!) then consider a full repair of the entire HVAC system including controls and heater core.

Yes, this will entail the complete removal of the front seats, dash, under-dash, steering wheel, airbags, and rear license plate.

Next up is locating, ordering and installing the necessary new parts.

Once everything is back in place and working as new you can schedule a spine-straightening at the local free clinic then jump in the 740 and tool around with the new blower fan on max while flipping that lever through all those positions on the dial.

George Dill

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Heat/AC control stuck 7 years 5 months ago #1633

  • billfrank38
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Thanks George, but I think I will pass on the full repair/replacement for the present time. Mostly I want to get this control unit operational, as I don't have any symptoms of core leaks.

It appears that the control operates by vacuum rather than any mechanical connections to the various doors and valves. Is this correct for this model?

Bill

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