Shark Attack

My problem is my Ac is not very cold. If it was low on fluid my compressor would cycle on and off. right?

When the ac is off the i get warm near hot air out the vents. It looks like in my WSM that it gets its fresh air from the engine compartment. would that not give me hot air even if the ac was off and the climate was slid to the cold side??

What I am chasing it to find out if my ac is getting cold but its trying to cool heated air. or if my AC is simply not getting cold at the core...

Thanks!
Kyle

nosnow

Sounds like you have a vacuum leak. Check to see if your heater valve holds a vacuum or if you have a vacuum leak somewhere else in the climate control system. If you do a seach on heater valve, climate control or heat you will pull up a lot of information.

As an aside when I turn my A/C off and the heater valve is closed I will still get warm air if I am not going very fast (stop and go traffic). The engine produces a lot of heat and the air intake for the interior seems to suck that hot air in.

dr bob

The compressor cycles on and off when the evaporator is so cold that it is frozen. When the system is low on freon but still has enough for the compressor to operate safely, it will be on whenever the AC button is engaged. (assumes that support electrical issues are all OK...)

The AC running with the slider temp set cooler than inside air temp will cause the fresh-air/recirc flap to go closed (recirc mode). There's a noticeable whunk! from the passenger's footwell area when the AC is first turned on. At that point it should be recirculating footwell air through the two exchangers in the dash.


When you first start the car cold in the morning and you turn the AC on right away (before the engine warms up..) you might see cold air at the center vent, followed my progressively warmer air as engine heat is added to the mix. Sound familiar? If so, it's likely you are facing a vacuum system problem. There are numerous diagnostic instructions for the vacuum system, including a pretty good one in the workshop manual. You'll need a Miti-Vac hand pump and an hour to do the diagnostic steps, then a bit more time to replace defective vacuum components inside the dash and center console areas.

If the AC just never gets cool even with the engine cold, you may find that you are low on freon. The original drier in my S4, as well as the replacement 944-style drier I have in there now, both have sight glasses on top so freon flow can be observed. The drier is a cannister, mounted to a bracket with tubing, in front of the radiator on the right side (passenger side on US cars). The sight glass is a little window maybe 8mm diameter. When the AC is running and engine RPM's about 1500, you can look through that little glass and see freon moving through there. A perfect system will have a nice liquid stream with an occasional bubble or two passing by the window. You may be able to see little streamers of oil being carried along in the liquid. As gas leaks out of the system over time, you'll see more and more bubbles in that sight glass, entrained in the liquid. Less gas equals more and bigger bubbles. More bubbles means that less of the total flow of freon will evaporate in the evaporator, and therefore less heat will be drawn into the evaporator from cabin air circulating through it. Same as "not as cold". So, do you have liquid, bubbles, or a pure gas stream with no liquid at all?


---- Many owners use a couple tie-wraps to hold the heater control valve actuator closed all the time during AC season. It reduces heat-soak issues after parking, and can help temporarily mask some vacuum issues that might allow the valve to open otherwise. At minimum, you can observe the valve actuator to make sure that there is vacuum there, drawing the valve closed when the AC is on and the slider is at the cool end of its range. Takes 10 minutes or so to do, most of the time spent removing the bottom of the air cleaner box for access to the valve.

Jim bailey - 928 International

The outside air comes in from the base of the windshield . The firewall and seal to the hood SHOULD keep the engine heat from that area. The A/C has a recirculation flap with vacuum pod just above the fuse and relay board the heater valve is held in the off position by vacuum as well. Often vacuum leaks bad pods let in enough air that the heater core has HOT water all the time.

inactiveuser1228

Kyle,

If you tie the heater valve closed with a zip tie and you still get warm air, it may be a bad valve. My car was doing the same thing as yours, and I attempted to fix the problem by holding the valve closed with a zip tie. Unfortunately, the seal in the valve had failed, and although the valve was held closed, water was still getting around the slide in the valve. Even though it was only a small amount of water, I felt like I was being cooked. For a temporary fix, I welded a plug in a piece of 1/2" emt pipe, and replaced the heater valve with it. Worked great until my wife complained one evening about not having any heat. Actually, other that the circlip that holds the headlight actuator arm together ($ 0.23), I think the heater valve is the least expensive part in a 928.

Steve

Shark Attack

i was just out looking at it. Their is a valve operated by vaccume under the airbox. it appears this lets hot water into the heater core. Is this valve open or closed when vacc is applied. I will alos check the one under the dash. I just want to get the ac going for the summer. I will worry abotu the vacc leak this winter during down time.

Shark Attack

I think this answers my above question. Ill tie er down and see what happens

thanks to all!!!

dr bob

Vacuum closes the valve. failure mode is "heat" so you can defrost the windshield. Same with the flaps -- failure of the vacuum system gives you full hot defrost flow.

dr bob

In the winter you will forget. "just getting the AC going for the summer" requires that you fix the vacuum system leaks if there are any. Otherwise the comb flap will block center vent airflow, your defrost flaps will be open to cool the windscreen, etc. You will need to replace the heater control valve if it's leaking. Refrigeration side issues need to me addressed correctly too.


Many of our cars are duct-taped and baling-wired together, rolling collections of all the temporary just-to-get-by-today fixes. Added up, they spell junk car. We wonder why typical resale values are so low...

DO IT LIKE YOU MEAN IT! FIX IT SO IT WORKS RIGHT, AND DON'T WORRY ABOUT IT AGAIN FOR ANOTHER 20 YEARS!


Local Big-5 sporting goods store has a sale on 80-qt coleman ice chests. Fill that baby up and leave the lid open while you drive. One of those little battery-operated fans taped to the edge manages air circulation. A cheap-and-dirty solution.

Shark Attack

No, I have a "down time list" I keep adding to.... but thats funny..

I just "tee'd" off the vacc line for the fuel pressure reg to the heater valve... yes I checked to make sure it held vacc with my vacc pump. I am pretty sure that was my problem. I will not know till I drive it tomorrow.

Thanks to all!
Kyle

Shark Attack

I still have to check this... without vacc I am sure its open... I'll fix that too. Then we should be cold enough for even chillie willie, remember him... Loony toon i think he was

dr bob

There's vacuum to the fuiel pressure regulator at idle and part or trailing throttle. No vacuum while accelerating, so every time you launch or shift, the heater valve will open.

There's likely a good reason why the factory did things the way they did, with the reservoir in th efender and the check valve and all.


Do the vacuum diagnosis just like you are going to fix things. If you want to wait until winter, you might decide to cap off the leaking solenoid circuit so at least the surviving vacuum actautors will work correctly. You can shop for diaphragms and plan the work at your leisure. The problem I see is that many half-fast temporary 'cures' like this are just band-aids over a stab wound. You hide the cut on the skin but the bleeding continues internally. Maybe internal bleeding is OK. After all, who knows what the band-aid is hiding?

killav

I had the exact same symptoms as your car. As Jim mentions above, my vacume pot above the fuse panel (which controls outside air) was bad, and the orange line running to the center comb flap was not connected. It had come apart at a flexible joint near the center console. The combination of these two vacume leaks also caused my heater valvle to not close fully. I fixed both vacume leaks and checked all of the others to make sure they were good. Heater vavle now shuts fully. My A/C has never been colder. Matter of fact, probably one of the coldest, most comfortable air conditioners I've EVER had in a car.

Shark Attack

Thanks, I drove the car yesterday and the AC was much much much colder. I will find this vacc leak this winter