92 S10 Truck Blows Air Out Floor Vent Only

[Dgreen]

Just converted this truck for a friend. Ac hasn’t worked in many years from the looks of things. Changed the compressor, accumulator, orifice tube, and added 6 oz pag 150. Pressures are good and lots of water coming from the evaporator, but air blowing in the cab is in the upper 60s and only blows out the floor vent.

[Dougflas]

Vacuum line is bad. Is this a 4.3 engine? Common problem.

[Dgreen]

It’s a 2.8 liter.
Any particular line or just start checking all the vacuum lines I can locate?

[Dgreen]

Also seems to be a lot of chatter from the clutch. I set the gap at .030. Is that too much?

[Dgreen]

I adjusted the clutch gap down to .022 and it seemed to be less noisy. Took the covers off the underside if the dash. Pretty sure I can hear a vacuum leak, but can’t tell which direction it’s coming from.

[bohica2xo]

Set the clutch gap as tight as you can without drag. .015 is good, it only wears bigger. .030 gap is too wide.

Locate the vacuum reservoir under the hood. It should have a line from the manifold, and one to the firewall. Trace the firewall line from the cab side of the firewall. If nothing is working the failure is in the main source line.

Reservoirs crack as well. Check the underhood lines and the plastic tank.

[Dgreen]

The rotary vacuum switch on the AC and heater control is leaking. No luck finding one locally so far.

[Dgreen]

I had some success! Greased up the vacuum control switch with silicone grease and reinstalled. We have cold air blowing out the vents! The metallic noise is still there. Only when the clutch is engaged. I took the hub and hub plate off and didn’t see any problems. Reinstalled the clutch and set to .015. Would a bad bearing make a noise only when the clutch is engaged? Also, I had to change the coil when I first started this project so the plug on he coil would match the style that is on the truck. Donor compressor is from an older model.

[bohica2xo]

Pull the belt off & check the pulley bearing. Try to rock the pulley. If it rocks, or feels rough, the bearing is on it's way out.

When the clutch engages it can pull a bad bearing in to a different location where it makes more noise.

[Dgreen]

Well, I changed the bearing and still have a noise. Also tried a different hub plate. Only thing I haven’t tried is a different coil and pulley. I put a stethoscope on the compressor and it sounds good.

Is it possible that the coil is weak and letting the clutch to slip and causing it to make noise?