AC Pressure Switch,Reverse PCV vacuum [Archive] - GrandAmGT.com Forum

PDA

View Full Version : AC Pressure Switch,Reverse PCV vacuum


Kebo
07-17-2008, 09:12 AM
I have two main problems. I have just bought this 2000 Grand Am GT with a 3.4L engine for my daughter. We drove it and everything worked and it drove out great. Before we got home the AC quit working so I thought it was probably just low of freon. However I could not get it to take any freon and there was freon in the system when I made the connection. So I am thinking it is the pressure switch but it has three wires...a red, a gray and a black. So I don't know how to jump it out to see if the system works when bypassing the switch. Help.
While checking out the AC I heard a vacuum leak. After checking for a while I found it to be coming from the line connected to the PCV valve. A little U shaped vacuum line attaches to the PCV valve and then to another junction box which looks like a solenoid or sensor of some sort. The problem is that when I connected the line to the solenoid the car went dead and then I realized that it is pulling vacuum into the engine (and rather strongly) instead of pulling vapors out of the engine. If you leave the vacuum line unplugged the car runs good but now the service engine soon light is on. The previous owner had just had the heads rebuilt. Any ideas or help would be appreciated.

Kebo
07-23-2008, 08:51 AM
AC problem is solved. I found a blown fuse in the fuse box under the hood marked get this "AC Comp". I should have checked that first! Anyway, I still have the problem of the vacuum pulling into the engine rather than pulling vapors out of the engine at the PCV valve. Any ideas?

timka86
07-23-2008, 09:34 AM
From what i understand, the black plastic tube that you are refering to goes from the front valve cover PCV valve over the intake manifold towards the rear, and has a rubber u-bend that connects to a small box, which has another plastic tube coming out of it, with a green label, that says 1-3 psi. that little black box is a evap solanoid.

so this plastic tube from the PCV to the solenoid, also taps into the intake manifold if you look under the black bracket that goes over this tube, you'll see where it goes, that's where the vacuum comes from.

there's another black tube that connects to the rear valves cover and over the intake manifold and into the intake piping (the rubber intake piping). check both of those for cracks.

i guess first go and check what the code is and get it cleared. it'll probably be a vacuum leak related. connect all the hoses and pipes as they were and see if the check engine light comes back.

Kebo
07-23-2008, 10:21 AM
Thanks. I'll check this out. I have never seen an engine pull vacuum into the engine thru the PCV valve. When I bought this car 1 1/2 week ago the previous owner had just had the heads rebuilt. While looking for the problem with the AC I heard a vacuum line sucking air. Thats when I found the little "U" shaped line was connected to the PCV line but was left unplugged from the evap solenoid. When I plugged it up it killed the engine almost immediately. Thats when I realized the vacuum was pulling in the wrong direction.

timka86
07-23-2008, 10:42 AM
well here's what happened with that. since the same tube is connected to the intake manifold right after the idle air control valve, and that tube was disconnected, the computer closed the AIC all the way, cuz air was getting in and it was idling just fine (cuz it was sucking air through that disconnected hose) when you plugged the hose back in, you totally shut off air suply and the engine choked. couldn't open the IAC valve fast enough. you'll be fine now. get that code cleared, or technically speaking, it should turn off in a few days if the problem was fixed.

Kebo
07-23-2008, 10:50 AM
Thanks. I'll clear the code...reconnect the vacuum line and see what happens. I appreciate the input.

Kebo
07-24-2008, 05:45 AM
timka86 you were right on. I cleared the code when I got home from work...reconnected the vacuum line...cranked it up and she runs great even better than before. I'm kinda thinking she's got too much power for my 16 yr old daughter now.

I have another question concerning the AC compressor fuse. I think it is #37 in the engine compartment fuse box. I found that it was blown on Sunday night. I replaced it and drove approx. 30 min. each day Sun-Wed and it worked fine, moving the fan speed and settings as need to keep it comfortable in the cabin. Last night (Wed) it blew the fuse again. I replaced it and it blew again in about 30 seconds. Any ideas? All I know to do is to start trying to check for a grounded wire. It has a 10 amp fuse and I had thought about trying a 15 amp but I don't want to cause a fire or melt down the wiring.

timka86
07-24-2008, 07:38 AM
timka86 you were right on. I cleared the code when I got home from work...reconnected the vacuum line...cranked it up and she runs great even better than before. I'm kinda thinking she's got too much power for my 16 yr old daughter now.

I have another question concerning the AC compressor fuse. I think it is #37 in the engine compartment fuse box. I found that it was blown on Sunday night. I replaced it and drove approx. 30 min. each day Sun-Wed and it worked fine, moving the fan speed and settings as need to keep it comfortable in the cabin. Last night (Wed) it blew the fuse again. I replaced it and it blew again in about 30 seconds. Any ideas? All I know to do is to start trying to check for a grounded wire. It has a 10 amp fuse and I had thought about trying a 15 amp but I don't want to cause a fire or melt down the wiring.

well different speeds wont have an effect on blowing this fuse that a separate circuit. This is A/C comp only. if you look down between the radiator and the engine you'll see the compressor at the bottom (belt side), there's a plug that turns it on, it sticks out kind of on an angle. there's tabs on the top and bottom that you have to lift to uplug it, kind of a pain,small screwdrivers are best (if you lift the car and remove the splash gaurd (same thing you remove to change the oil filter)) it's easier to reach from the bottom. you should be getting 12 volts there when you turn on the A/C (car has to be running) so one of those wires is a positive and the other is ground. follow the wires to see if they're crimped/melted maybe the connector is wet/dirty.

You can even try and unplug it, start the car and turn on the A/C and see if it blows the fuse, if yes you have a short in the wires an it's not your compressor so start looking for where the damage is. most likely melted cuz they run so close to the exhaust.

If it is a short somewhere, a 15 amp fuse will fry as well.

Kebo
07-24-2008, 08:08 AM
Thanks for the reply. I'll give this a shot this evening and see what I can find out.

Kebo
07-29-2008, 12:33 PM
Well it seems to be the A/C clutch coil. I have ran the vehicle with the A/C on and the compressor unplugged over the weekend and the fuse has not blown. When I plugged the compressor back up it blew the fuse. So...to replace the coil the clutch has to come off. My question is will this all drop down below the engine enough to do this repair...or can I access thru the fender well...or am I gonna have to disconnect the freon lines an remove the compressor to replace the coil?