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Discussion Starter · #1 ·
Here's a strange one:<p>I am in the process of replacing the headliner in my '90 760 TW. While I have it out, I figured it was a good time to repair the sunroof. After I dropped and removed the sunroof assembly, I found what seemed to be a vacuum line coming out of the passenger’s door pillar and ending at the center of the roof. It appears to have what seems to be a broken nipple at the end of the hose. It is open and not terminated.<p>After a little exploring, I found that it is linked to the intake manifold through the climate control in the dashboard. With the engine running, it is indeed trying to draw a vacuum.<p>Does anyone know what this vacuum line is doing in the roof and what it might be for? Should it be closed off or left open? My inclination is to terminate it and eliminate a leak.<p>TIA<p>Ed<br>
 

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Re: Vacuum line in roof? (gdill2)

Yes, it does. But the hose will only reach to the center of the roof behind the sunroof panel or as far back as the rear of the passenger door. The hose is not rubber, but a stiff plastic, light in color.<p>Ed
 

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Re: Vacuum line in roof? (gdill2)

Yes, it is electric, positioned in the normal spot at the windshield. I am not aware of any vacuum powered devices in the roof or vacinity, standard equipment or optional. <p>The car was three years old when I bought it, and a new headliner was put on at that time. However, they did not replace the headliner on the sunroof panels. So, I am sure that the sunroof assembly has not been removed since it was built. The gaskets had not been disturbed. <p>The vacuum hose was routed into the back of the drain pan. Maybe it's there to suck out the rain water or lower the air pressure under the sunroof so it's not sucked out at high speeds. Juuust kidding.<p>I've been driving and fixing Volvo's since '69 and I've never come across anything like this before.<p>Well, thanks for your time, George.<p>Ed
 

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Re: Vacuum line in roof? (Edjec)

Update:<p>After I had the headliner shell reinstalled, all of the side panels replaced and the sunroof finished, I went to install the central interior light. What do you think I found? A broken nipple on a small black box located front center on the light assembly. From the users side there is a small hole located on the front between the two lamps. <p>That hole allows the vacuum line to draw air past a thermistor that measures the ambient temperature of the cabin. With this disconnected, the air conditioner will only turn on to max if the temperature control is turned to 64 degrees and it will stay on max. When properly connected, the air conditioner will initially max out at any temperature setting and then drop to the setting of the temp control.<p>So, there we have it; the vacuum line in the roof is for the air conditioner. <p>Who’d a thunk?<p>Ed<br>
 
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