When you press the AC button (to turn the AC on) - does that change any settings of the vacuum solenoids, or anything else in the vacuum system in the console?

I hear a hissing sound as soon as I turn on the AC. There is no cold air coming - even in the coldest position.

The AC evaporator was replaced with a used one last year. vacuum actuators were replaced also.

 

Yes, it does change. There is a nice table in the WSM that explains what the different HVAC and AC buttons do. I haven't access it them right now though, sorry. But the short answer it yes.

 

Nicole--

Without consulting the table.... The comb flap actuator, hiss will be forward (in the car) of the console area right in the middle. Might hear it through the center vent. You can usually see the comb flap move easily if you pop out the center vent assy. Footwell flap closes if selector is not on footwell or combo foot'defrost position, hisses will be heard lower right console, forward of the radio area, regardless of AC on or off. The fresh air vent door will usually clunk depnding on temp setting and outside air temp; hot outside and lower slider setting will close that when you first turn AC on. Flap is above the CE panel, pass side footwell. Dash defrost vents will close if selector is not in defrost or combo footwell/defrost position no matter whether you select AC or not. Heater valve opens based on outside temp, slider temp setting, inside temp. Closed for sure if slider full left.

In my limited experience with these things, start out with a Miti-Vac diagnosis of all five vacuum circuits. One or two leaking will cause multiple other symptoms, so the Miti-Vac is really the only definitive way to find the root cause.

You have one relatively easy-to-change device at the heater valve, and yours has undoubtedly been changed sometime in its known past. The rest are all a little tougher to access. Since they all work pretty much every time you start the car, it's best to do all of them even when just one or two happen to be leaking right now. Center vent and footwell flap can be done after removing the console. Defrost requires the pod to come out. Fresh air flap is done from both the top of the engine bay at the base of the windshield and from the pass footwell areas. There's plenty of documentation on those so I won't duplicate.

 

Good stuff Dr Bob. Quick and easy before diving in to the console solenoids is to check vacuum at the main feed in the engine bay, by the fire wall. I think it's the black hose that goes thru the firewall.

 

From the WKD 496 921:

 

I don't think that simply turning the A/C compressor on changes any vacuum device.

The hissing might well be refrigerant flowing into the evaporator, and if so is normal.

The lack of cooling might be due to other causes...

 

In the vacuum system that operates the vents, nothing changes by just pressing the A/C button. If you don't have cold air coming through, when you press the button, the only real possible cause in the vacuum system would be the heater valve.

Giving the benefit of doubt, I'll assume your evaporator was installed correctly along with the vacuum solenoids. I would guess your lack of cold air is coming from the A/C system itself. Your evaporator was replaced. Anything else? There are over a dozen points in the system for leaks to occur (4 at the expansion valve, 2 or 3 at the drier, 4 at the connections to the compressor, 2 at the fuel cooler, 2 at the condenser, and a few others.) And probably two dozen places if you have rear A/C.

When you hit the A/C button, instead of listening for the hiss, pay attention to the engine speed. Does it change briefly when the clutch engages? Or you can turn it on and visually check to see if the clutch is engaged.

 

Nicole even though you said that the pod diaphrams have been replaced i would recheck them with the mytivac, sometimes the new parts can slide out of there housings and create leaks, this could explain the air your hearing

 

It seems on my car that the fresh air flap cycles closed when temp slider is set colder than ambient, then the AC button is pressed. I here it clunk shut then. Makes sense that the flap would go to recirc position only when you are actually cooling the car; otherwise, outside air is circulated into the cabin.

Depending on the charge level and the expansion valve operation, you may hear some hissing as the liquid flashes in the evaporator. You can eliminate this by testing with the compressor clutch unplugged at the front engine harness connection by the oil dipstick tube. No hiss from refrigerant when compressor isn't turning.

 

Thanks, I have not had the time to troubleshoot this in more detail. What we noticed today is that if I close the center vent, the hissing goes away. But when I tried again later, it seemed like the hissing was just muted behind the closed vent.

Still no cold air, though.