Now what?

Based on suggestions from members like Bill Curlee I have a tester to test the ac diaphragm due to the "all vents" issue.

But since I have a shiny new tester I figured maybe I should, just for shines and giggles, test the vacuum of the engine to ensure there are no issues internally there.

so:

1) When I disconnect the intake vacuum hose from the ac diaphragm, what should the vacuum read there?

2) Where should I test the engine vacuum? Closer to the valves, or throttle body? Which connection will be more accurate in telling me if there is a hidden issue?

3) What should engine vacuum be at that connection?

Thanks

 

Here's a link to the instructions for the vacuum tester I just bought (Actron CP7803). Hope it helps.
http://www.e-servicemanuals.com/prod...od_id=13287803

To answer question #3, a steady reading from 15-22 inHg is what you are looking for during the "running vacuum" test. If it deviates, you may have an issue somewhere. Any vacuum source should be sufficient as a test point (question #2).

For question #1, one suggestion would be to first perform the running vacuum test, then check the vacuum supply to your vent actuators. I would think that they should be fairly close. Any major deviation could be a possible cause of your vent issue.

Is there any particular operating condition in which your vents don't work? Is there any particular operating condition in which your vents do work? It may also be beneficial to check for exhaust restrictions. Raise the rpm to 2000 and look for any changes in the vacuum reading. A gradual decrease indicates a restriction. This might be affecting your vents as well.

Good luck...post up your findings and let us know how things work out.

 

Most vacuum test are manifold vacuum. Most "stock" engines have 15-20 " of vacuum at idle.

 

On the back of the intake manifold, is a small fitting. There is a very short very thinn NYLON vacuum line that connects to it with a 90 deg rubber fitting. That line runs inside the engine wiring harness, under the battery and down to the vacuum resivour container. There is a set of "T" fittings and some check valves. One og those lines supplies the resivour and one goes to the HVAC solenoid manifold. That vacuum line to goes to that solenoid manifold needs to see full engine vacuum.

IF,,,,,,,,, that line is broken somewhere, you will NOT have control of the DAMPER DOORS and the HVAC Fan air will flow out of multiple locations or where the damper doors failed to the position that they are currently in. In other words, you will be UNABLE to control where the air comes out.







I got tired of struggling with the short hose staying on the fitting during manifold reassembly that I lengthened the hose!





On a side note and completely off this topic; This is a 2002 ZO6 LS engine. In stock OEM form, the rear cross over vent tube is BLOCKED OFF with two plugs. I desired to retain the use of the rear vent tube and installed a 2001+ front vent tube in the rear. Its flipped 180 from the way its installed in the front. I ran a small 1/4" rubber coolant hose to the front and used a "T" fitting to plumb it in to the front coolant vent line!


This picture shows the nylon hose in OEM STOCK SHORT length. Talk about a PITA to work with!!!!