1993 Taurus A/C vent fix (and Vacuum and Water Distribution Manifold purpose question).

Hi,
I just had the A/C compressor replaced on my 1993 Taurus GL (3.0L). A week later, we noticed that the A/C vents in the car would close when the car was put under medium acceleration. At idle, or once the car
was up to speed, the vents would open up and the interior would get cold as desired. I know that the vents are vacuum controlled, so I suspected some kind of vacuum leak caused by a hose that was left off or possibly cracked during the compressor job. I swore it was something that the mechanics had screwed up (but it wasn't - read on).
Today I pulled off the engine manifold vacuum port hoses. These two hoses are at the intake manifold vacuum port, and are about 1/2 inch diameter hose (normal stuff so far). I plugged one on the hoses, then did a little suck job on the open hose. After a little acrobatic positioning, I was able to hear the vacuum leak on a little 1/8 inch line that runs into the firewall, right where the heater core hoses pass into the firewall. I spliced that 1/8" line and the vent problem was solved. Nothing too exciting there. But there's more . . .
The 1/8 inch hose that I spliced, runs from the center of the firewall (where it passes into the dash), over to the passenger side (USA car). Just about in front of the passenger, below where the hood hinge is, there is a little 2"X2" plastic box bolted to the firewall. That 1/8" line connects to that box. Also, both the 1/2" manifold vacuum supply lines also run directly to that box. There are a couple other "output" vacuum ports coming off that box that supply vacuum to the normal vacuum manifold that's in front of the driver (for power breaks, pollution control, etc.).
Now what I think is odd is that this little black plastic box in front if the passenger, also has an input port coming from the (electric) windshield washer pump outlet. Then there's a water outlet port that goes (as expected), to the windshield washer sprayer nozzles. Here's what is interesting: When I spliced the little 1/8" cracked vacuum line that feeds the A/C vacuum motors, I noticed that there was a little wetness oozing out around the crack. I put a hose on that 1/8" line to see if any water would be sucked out (and also to make sure that my vacuum motors were hold a vacuum). Thankfully, I did not get a nasty drink, and the dash side off the line held it's vacuum.
This little black box with both water and vacuum lines attached is technically called a "Vacuum and water distribution manifold". It has no electrical connections. I have a digram of the box and hose assembly if anyone would care to take a look. For the life of me, I cannot figure out why the (electric) windshield pump water should go anywhere near the car's vacuum system. Does anyone have any thoughts on this ???
I will greatly appreciate your comments and experience.
Regards, Brcobrem
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I had it happen in my 90 and it was a leaking vacuum motor under the dash. As you stepped on the gas, the airflow would change from one set of vents to another. you got a vacuum leak somewhere.
Bob
Brcobrem wrote:

-
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"BOB Urz" wrote

Uhhh.... yeah. He mentioned that in the second half of paragraph 2......

Any help with the rest?

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Hi Bob and Masterblaster,
Thank you both very much for the feedback. Since the original post was a little long winded, I'll restate the advice I'm looking for, as follows:
"This little black box with both water and vacuum lines attached is technically called a "Vacuum and water distribution manifold". It has no electrical connections. I have a digram of the box and hose assembly if anyone would care to take a look. For the life of me, I cannot figure out why the (electric) windshield pump water should go anywhere near the car's vacuum system. Does anyone have any thoughts on this ??? "
Anyone have any thoughts why the (electric) windshield pump water should go anywhere near the car's vacuum system.?
Regards, Brcobrem
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wrote:

No, but if there's coolant water in there the block will act as a heat exchanger of sorts - warm up the windshield washer fluid being sprayed so it will melt ice a little as it is used.
Only practical reason I can come up with.
--<< Bruce >>--
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Thanks for the (possibly good) idea Bruce. But alas, there's no coolant water to that block, just windshield pump going in and then out to the wiper nozzles.
Since the total run of the hose from pump to nozzle is about 4 feet, perhaps they had a ton of 2 foot hoses left over and just needed a way to connect them in the middle. Who knows. . .
Regards, Brcobrem

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"Brcobrem" wrote (1993 Taurus)
There is a little black box called a "Vacuum and water distribution manifold" with both water and vacuum lines attached. It has no electrical connections. I wonder why the (electric) windshield pump water should go anywhere near the car's vacuum system. Does anyone have any thoughts on this ??? " _____________________________________________________
Combining several functions in one device is a common cost-saving technique in manufacturing. Both manifolds are molded as a single piece by a supplier, eliminating the cost of buying, inventorying and installing one of the manifolds. It is not necessary for the device functions to be related to each other.
A good example of cost savings from combining functions is the multifunction switch. Manufacturers no longer have to buy, inventory, and install separate turn signal switches, wiper switches and headlight dimmers. They have all of the functions provided in one device from a supplier, and it only has one installation point. Some of these switches combine even more functions.
Rodan.
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Hio Rodan,
I'm going to bypass that box (and cap it's water ports) and see if the windshield gets wet. I can see no reason why it's required (other than they had a ton of 2 foot hoses in stock and using the block was a way to get a 4 foot run).
Regards, Brcobrem

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