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2003 Saturn L300 AC will not turn on!

Tiny
ALAUMD88
  • MEMBER
  • 2003 SATURN L300
  • 154,000 MILES
AC compressor will not engage. Adequate pressures in system (100 high side) for clutch to engage. Relay works fine also. Control Head has malfunctioning LCD display with 2 bars in the digits missing.

How to check for signal from Control Head to BCM calling for compressor to turn on? How to check for signal from BCM to ECM? Have Auto Climate Control control head. How to check if AC pressure switch is not working? I know compressor clutch is fine coz it will engage if I short the ECM AC power control relay to ground.

Where to find an accurate schematic of the Control Head to BCM circuit for the proper connectors? The Saturn HVAC service manual I have gives different wire colors and positions on those connectors than what is under the dash so I am totally confused!
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Tuesday, July 23rd, 2013 AT 9:32 PM

36 Replies

Tiny
SATURNTECH9
  • MECHANIC
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I posted a reply to you on another users question posted on to start your own question before I saw this one. Anyway you can snap a pic of your climate control display? I may have an idea of whats going on here. Also with a auto climate ac it makes it much harder for a diyer to diagnose. There is a computer in your ac control head that requires a professional scan tool to read codes in it see data inputs in it etc. The diyer scan tools can't do that.
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Tuesday, July 23rd, 2013 AT 11:33 PM
Tiny
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Do you want the snap shot with the control head on, lit up or off? How do I get to the other reply you wrote for the other user's posted question?
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Wednesday, July 24th, 2013 AT 6:04 AM
Tiny
SATURNTECH9
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They keep changing everything on this site so its hardto keep track of searches eetc.I know you can select Saturn or cars models and search by ac.I would like a pic of the control head screen all lit up with the display on. So I can see what it looks like.
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Wednesday, July 24th, 2013 AT 11:53 AM
Tiny
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Here is the control head. The back lighting went out after I switched out the head with a used one from LKQ which turned out to be bad as well. It may not be apparent but there are 2 missing bars on the LCD digit display. Also the pic you see is what it defaults to 5 sec after messing with the controls. Does not make any sense to me (-19 degrees?). I have ordered another control head from LKQ arriving tomorrow. Hope it is a good one that works.

Do you have any idea about repairing the circuitry on the board inside the control head?

Thanks so much for your interest!
Abel
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Wednesday, July 24th, 2013 AT 7:00 PM
Tiny
SATURNTECH9
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Now were getting somewhere that's why I wanted to see the LCD display. You see how it says -19 then below it says ext?That means it thinks outside temp is -19 so it won't allow the ac to work. There is a outside. Temp sensor for the ac in the front grill area towards the center. See if its plugged in and the wires too it are good?I have seen this before that's why I wanted to see a pic of the ac display.
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Wednesday, July 24th, 2013 AT 8:11 PM
Tiny
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Oh wow! Ok I will certainly look in the AM. I know this car front end was hit because the condensor had a hole in one corner where the bracket was busted holding it to the radiator. Have also noticed 2 loose wires dangling near the bottom of the right fender, if I remember correctly. Both fender wells are missing the splash shields and plastic barriers covering the bottom side of the engine bay.

Thanks for the insight! Will let you know tomorrow after work.
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Wednesday, July 24th, 2013 AT 8:51 PM
Tiny
SATURNTECH9
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Sounds like a wire issue from your description
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Wednesday, July 24th, 2013 AT 9:29 PM
Tiny
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No sensor on the grill anywhere. 2 wire connector (purple and black wires) hanging down near driver side fog light hole (also missing) Is that the sensor connector?

Also how to fix the back lighting on the control head?
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Thursday, July 25th, 2013 AT 6:11 AM
Tiny
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Have you looked below the grill in the bumper opening?Not sure what the colors of the wires are will have to look them up. Let's worry about the back light after we get the ac working
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Thursday, July 25th, 2013 AT 7:00 AM
Tiny
SATURNTECH9
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The wire colors are light blue and the other wire is black. It shows the sensor over by the left head light area by your cooling fan relay box.I guess I was wrong the earlier cars were in the grill area. Let me know what you find.
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Thursday, July 25th, 2013 AT 7:18 AM
Tiny
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Found the bare yellow/black wires which are not attached to a connector hanging down on driver side below & behind bumper. [The purple/black wires are for the fog lights.] Without a pic to show how the wires feed into the connector, how do I know which side to connect the yellow wire to on the temp sensor? Should have a new temp sensor in hand tomorrow after work. I don't want to mess up the sensor by connecting the hot wire to the wrong side.
Thanks so much for your interest.
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Thursday, July 25th, 2013 AT 8:36 PM
Tiny
SATURNTECH9
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In my wire diagram I see light blue wire and a black wire unless there that color I would say my wire diagram is wrong or you found the wrong wires.
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Thursday, July 25th, 2013 AT 9:43 PM
Tiny
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In the 2002-2003 Saturn HVAC service manual the schematic shows a Lt Blu wire out of the Control Head but for 2003 year only, apparently that wire splices with a yellow wire before ending in the connector.
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Thursday, July 25th, 2013 AT 9:54 PM
Tiny
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If that's the Saturn service manual we will go with that one. Terminal B is the black wire. Also the yellow wire is terminal A.
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Thursday, July 25th, 2013 AT 10:26 PM
Tiny
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How to tell which pin in the sensor goes with the yellow wire or black? The connector is gone - just bare wires hanging down. Does it matter if I reverse the connections?
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Friday, July 26th, 2013 AT 4:52 PM
Tiny
SATURNTECH9
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You need to buy a new connector an the terminals on the connector labeled A and B.I will look for a connector for you.
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Friday, July 26th, 2013 AT 5:46 PM
Tiny
SATURNTECH9
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Rock auto. Com has re connector you will have to the oic to your swsor they show two different ones.
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Friday, July 26th, 2013 AT 5:53 PM
Tiny
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I shorted the 2 bare wires and the ext temp read 140 and the compressor kicked in! Haaaaaallelujah!
Now does it matter if I reverse the wires to the ambient air sensor? I don't want to damage it!
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Friday, July 26th, 2013 AT 5:55 PM
Tiny
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Sorry didn't see your answer about the connector being labelled. Actually had it in my shopping cart at rockauto since last night. So will go ahead and get it now.

Now, the compressor runs fine but the low side pressures jump up to almost 100 when I try to charge the system. It has less than 10 oz of R134a in it presently. High side will not rise above 140. When I shut of the flow of refrigerant into the low side, the low side comes down to 30-35 but no lower, even if I rev up to 2000 rpms. Revving does not change the high side at all; the needle seems to waver a bit actually. I do not believe any refrigerant is actually flowing into the system with the valve open (can does not get cold) due to the almost 100 low side pressures that won't come down with revving.

So is my compressor done for? It seems that it cannot compress good enuf to lower the low side and raise the high side. What is your opinion?
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Friday, July 26th, 2013 AT 6:04 PM
Tiny
SATURNTECH9
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When you open the can your measuring the pressure in the can at that point. So of course the pressure will use to 100 or ore on he low side. What I do is charge it with he ac off till it wont take anymore. Then turn the ac and put the rest in till its completely charged. Some cars hard to change with thisse 12 oz cans. Till you get it fully charged I wouldn't be looking too had at the pressures and saying this or that is bad.
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Friday, July 26th, 2013 AT 7:42 PM

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