weird static noise in A/C idle up vacuum circuit (1 Viewer)

Joined
Sep 27, 2006
Messages
1,157
Location
HI
 
 
Hey all, I have a 1985 FJ60 Desmogged non HAC setup. The noise did start after the desmog. Basically, the noise sounds like static coming from the rear side of the engine near the manifold/carb section. It's definitely cause by a vacuum tubing. I can pinch the tubing, which gets manifold vacuum, and the noise stops. I can disconnect the tube and the noise stops. Disconnecting or pinching the hose coming from the A/C diaphragm does nothing. The pictures are from the desmog thread. The tubing I'm talking about runs from the driver side fender going to the back on the manifold, where there is a nipple. Just above this nipple is where the brake booster gets vacuum. The pictures are from the desmog thread and they are of my setup. The tube that gets pinched is the one with the red lines heading to rear of the engine. The other red lined tubed goes to the A/C diaphragm. The connection between those two is the stock connect with some sort of adjustable dial and two electrical wires coming out.


 

2mbb

SILVER Star
Joined
Sep 1, 2003
Messages
5,021
Location
WC, CA
 
 
 
The AC idle up valve opens to let the manifold vacuum access the AC idle up diaphragm when the AC compressor turns on. When the compressor turns off, the valve closes, and the vacuum to the diaphragm is vented to release it. So this valve is more like a 3-way valve because it connects the tube to the diaphragm either to manifold vacuum, or to the atmosphere. My guess is that you have the tubes switched on the valve and the tube that goes to the manifold vacuum is being vented to atmosphere, when the valve is turned off. Switch the tubes and see if the noise goes away.
ac idle up.JPG
 
Joined
Sep 27, 2006
Messages
1,157
Location
HI
 
 
Thanks so much! I should have tried that right away! :doh:
 
Joined
Sep 27, 2006
Messages
1,157
Location
HI
 
 
Oh! Does that dial do anything? It doesn't seem to affect anything.
 

2mbb

SILVER Star
Joined
Sep 1, 2003
Messages
5,021
Location
WC, CA
 
 
 
Is it a dial or an air filter? If it does anything, I would suspect that it limits how quick the air bleeds back in to better control the RPM drop when the AC idle up is turned off. But I have not found any real description of these components in the FSM's.
 
Joined
Sep 27, 2006
Messages
1,157
Location
HI
 
 
I'm not sure. I think it's a dial, or rather I don't think it's an air filter as I've never heard anything about that and it doesn't seem like an air filter is needed there. Perhaps it's just a covering that turns.
 

2mbb

SILVER Star
Joined
Sep 1, 2003
Messages
5,021
Location
WC, CA
 
 
 
OK. found it on the last page of the FSM. The cylinder at the end of the VSV is a filter (item C in the figure).
ac vsv.JPG
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top Bottom