need help !!

STORMY · Post by **STORMY** » 11 Aug 2006, 18:34

I have an 89/ 780 bertone volvo and the a.c. has been fine till today
the a.c.was blowing fine then it stoped blowing through the middle vents and now only blows though the side vents by the door . its blowing cold but just from the side vents . Is this a vacuum hose or what and if it is do you have a diagram so i can locate the leak

Post by **MadeInJapan** » 11 Aug 2006, 20:34

Stormy, as much as I'd like to help you, I know nothing about your car. I would think that there may be dampener motors in your A/C ductwork that opens and closes vents and this (or maybe there's more than one) has broken or has corrosion and has stopped working...I don't know. Ask around your area and see if anyone knows a good independent mechanic that works on Volvo's. Your car is an 89, so there may not be much electrical stuff in the ducts and it may be mechanical...like some piece of plastic that opens and shuts certain vents may have broken, or it may be even simpler...a piece of duct has come out of place and fallen down under the dash. Can you look up under there from the floor and see such a thing? Again, I'm just guessing at this point. If you turn the heat on, does it come out of the center vents, or is it just with A/C?

Also, you might want to post your question here: https://www.matthewsvolvosite.com/chat/p ... um.php?f=2
rather than the For Sale section of the entire site.

STORMY · Post by **STORMY** » 11 Aug 2006, 23:08

thank you , and for the heat it does the same thing .. i'm guessing the vacuum hoses because i had a astro van once that did the same thing but to find out for sure i need a diagram to trace down the leak if this is the problem.. if you have one please reply &post it here thanks

Post by **MadeInJapan** » 12 Aug 2006, 05:47

I'm up early...planned to sleep in but somehow I woke up. Anyway, you are confusing "vacuum" hoses with the AC system. There are not vacuum hoses in this system. Vacuum hoses are found in the engine compartment, and some are part of the crankcase system. Now, with that out of the way, I don't have a diagram of the piping or vent system of your AC...sorry. But like I said, look for disconnected plastic (large, I would think) vent hose in or under the dash as well as some type of louver or flap that opens and closes to allow air into the middle of your dash. Something is broken or disconnected. I don't think it would be motor driven in your '89 Volvo (such as dampener motors) but I could be wrong. Not sure how ahead of other cars Volvo was with their climate control system at the time of the build. As I said before, if you can't figure it out, try finding a good volvo mechanic.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 12 Aug 2006, 08:29

The problem with your vent controls is all too familiar to me. Below is a copy of what I posted on this subject in the RWD forum two years ago. Read throught this and let me know if you have any questions.

I don't need help with this one because I figured it out myself. However, others may learn from my experience.

Shortly after I purchased my car, I discovered that the A/C vent controls did not function. The fan switch worked well, but I would only get air flow through the Defroster vents no matter what vent position I selected. Also, air would be slightly warm no matter the position of temperature control. I also discovered the A/C belt removed from the compressor and the A/C clutch wiring purposely disconnected.

The previous owner had the car serviced at an independent Volvo garage in the "People's Republic of Berkeley", California. Two years ago, the shop discovered that the controls did not work and quoted $250 to repair, though they didn't state why they would not function. On the same repair bill, they charged a fee to remove the A/C belt and to replace the temperature control valve. Then, ten months ago, they replaced the temperature control valve again, for whatever reason.

I quickly discovered that these controls required engine vacuum to operate. I found two vacuum tubes that passed through the firewall. One went to the heater control valve. The other to a tee in a large diameter vacuum line. One end of the large line attached to the intake manifold. The other end went somewhere under the left side of the car. I looked under the car and found the line attached to a long, cylindrically shaped, plastic tank, mounted forward of the front crossmember.

I disconnected the main vacuum line from the intake manifold and plugged the tap. Then I disconnected the vent control vacuum line from the tee, attached a hand-held vacuum pump, and pumped down a vacuum in the vent controls. I quickly found that the vent controls operated normally as long as I kept a vacuum on the controls. This told me that I had a vacuum leak somewhere on the main vacuum line.

I went back under the car and unbolted this plastic tank from the undercarriage. It is held on by three bolts. Once I got it out from under the car, I easily saw the large crack that traveled half way around the far end of the tank. No wonder the vent controls did not work, there was no vacuum in the line. Not only that, the car had a major intake vacuum leak that went undiagnosed for over two years, and the independent mechanic that had serviced the car all that time, saw the clues, but was too blind to figure this out!!

This tank is positioned in such a manner under the car, that it is the first thing to be hit by large debris on the roadway. It appeared that the crack was cause by blunt force trauma from road debris.

The purchased a new vacuum tank from my local Volvo dealer for $47. For good measure, I replaced the vacuum line between the intake manifold and the vacuum tank. Once installed, the vent controls worked like new. I then replaced the A/C compressor belt, reconnected the clutch wiring, and now the A/C blows 40 F air in the coldest position. I don't think I would recommend that independent Volvo garage to anyone I know.

So, if your vent controls stop working, be sure to check for vacuum and the condition of this tank before trying to take apart your dashboard controls.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 12 Aug 2006, 09:23

I want to add a couple more things. Your 780 Bertone is a rear wheel drive (RWD) Volvo based on the 740/760 series Volvos. It is mechanically equivalent to the 740/760's and approximately 90% of the mechanical parts interchange.

When posting new threads on this web site, I suggest using the RWD forum, the one labeled "Volvo 240 740 760 940 960". Thats where all of us with the RWD Volvos hang out. Also, a quick description of your problem in the Subject line is helpful for those of us scanning the messages. And it helps when others search the forum for similar problems.

Welcome to this Volvo Site. We are all here to help each other out.

Post by **MadeInJapan** » 12 Aug 2006, 09:39

Wow...great reply, Kmaniac!

Even if the original poster isn't able to do it him/herself, at least he/she will know where to get a good independent to begin looking.

Sorry that I couldn't help. I tried to think logically about the A/C but me being a FWD man and not knowing anything about pre '94 Volvo's I was stummped and surprised to find that it is Vacuum related after all.

And I agree with you...the for sale section is not the best place to post such a thread.... I suppose it's all a learning experience.

STORMY · Post by **STORMY** » 13 Aug 2006, 00:31

thanks for the help . could you be more descriptive of where this "tank " is under the car. Not much on finding things on this car thanks again

Kmaniac in California USA · Post by **Kmaniac in California USA** » 13 Aug 2006, 09:00

The Haynes Automotive Repair Manual for "Volvo 740 & 760", #97040(1550), on page 22, shows a photo of the undercarriage, with the vacuum tank labeled as item #4. Now, you may have to remove a moulded rubber splash shield to see it (the splash shield was missing from my car when I bought it).

If you don't have this repair manual, I suggest you get it. They did not make a special repair manual for the 780 since Volvo only made 8,500 of them between 1984 and 1990. The 740/760 manual will have everything you need, at least mechanically, since all these models are mechanically equivalent.

The vacuum line routing for the vent controls is very simple and I will describe it verbally. At least on my car, there is a 3/8-inch diameter vacuum hose, where one end connects to the intake manifold and the other end to the vacuum tank. Part way down the hose there is a T fitting, where the small plastic tube for the vent controls attaches. You will also find a check valve on the large line between the T fitting and the intake manifold. Nothing else attaches to the big vacuum line. The small plastic tube runs straight to a grommet in the fire wall. From this same grommet, you will find a second plastic tube that runs to the heater control valve, located between the back of the engine and the fire wall.

You need to focus on the integrity of the plastic tubes, the large vacuum line and the vacuum tank. A leak, break, or disconnection under the hood is most likely the cause of your problem. Check out everything under the hood of the car first before trying to dig under the dashboard.

I hope this helps. Let us know what you find and what you do.

Post by **JRL** » 14 Aug 2006, 20:38

Oh boys, this is a FOR SALE section.
(Dave, you know better than to continue this here)
Move this conversation where it belongs