# 03 chevy malibu a/c problem ??



## oren (Jul 8, 2012)

Hi all, i have aa 2003 chevy malibu. A/c worked fine until it got really hot then it quits. When i press the a/c button the light comes on, the fan blows air but the compressor is not kicking on. I checked pressure at low pressure port and it reads about ambient temp without car running. I hooked up water hose and sprayer to cool condensor and hot wired the compressor relay terminal, and the compressor came right on and blows cold air.Als with the gauge still hooked uo it reads about 32 lbs or about mid way in the blue area. I have also replaced the coolant sensor since i did'nt know if it had anything to do with it. The malibu only has a pressure sensor on the high side line which is called a transducer, i beleive, and i have switched it with one that works off another vehicle, but still no a/c. I even removed the control head from dash and cleaned it like the instructions called for on another post, still nothing. All fuses and relays check out fine. I'm really at a lost here and could use some good help. Its my 17 yr old sons car so trying to save him a little money....... thanks


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## octaneman (May 13, 2009)

Hi oren


Swap the A/C relay with a known good one and re-start the compressor. Does the compressor come on ?


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## oren (Jul 8, 2012)

thanks for your help. I already swapped the relay with 2 different ones known to work. I am getting no power to the compressor. But i can take the connector off the compressor and hook alligator clips to the the terminals and hook to battery and the clutch will engage, and if i have the car running it will blow cold air.


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## octaneman (May 13, 2009)

Do a continuity test from the A/C switch to the relay , double check the feed to the switch. If the compressor turns on by jumping the terminals on the fuse box ,the problem lies with relay ground or the controler.


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## oren (Jul 8, 2012)

i do not have a electrical diagram of this car (local store or library does not have one). How can i tell which terminal that the relay plugs in goes to the compressor. Or what would be the correct way to check the relay terminals.


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## octaneman (May 13, 2009)

For schematics goto AutoZone | Auto Parts & Accessories | Repair Guides & More


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## oren (Jul 8, 2012)

thanks i just printed them out, now if i can just figure it out.


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## oren (Jul 8, 2012)

should'nt you be able to hear or feel the compressor relay #16 click when you either switch the ignition on and press the a/c button to call for air with the fan in run position. I can easily feel the fuel pump relay click when i turn on ignition. Can you tell me how to check the relay socket and which slots should have the correct values using a volt meter. I don't have any experience reading schematics. Here are the schematics you referred me to ..thanks...| Repair Guides | Heating, Ventilation & Air Conditioning (2003) | Hvac Systems - Manual | AutoZone.com


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## octaneman (May 13, 2009)

Oren, 


The relay should click on the moment you press the A/C switch. When you look at the diagram you see the relay has 4 pins, from the fuse power is distributed to coil and to the trigger side of the relay. The coil side of the relay also has a resistor which acts as a current limiter. The coil is grounded to the PCM's A/C clutch relay control via a dark green wire with a white stripe (DKGRN/WHT). When you turn the A/C switch on, the PCM closes the switch circuit by grounding the relay, the coil is energized creating a magnetic field which pulls the relay's trigger switch on. Power is then connected to the trigger of the relay which connects the dark green wire (DK GRN) to the A/C clutch, the A/C clutch turns on effectively spinning the compressor. The A/C compressor also has a diode connected to it through a grey wire (GRY), which makes the compressor stop on a dime in case of voltage feed back when power to the compressor is turned off this is called dynamic braking. 


When you don't hear the relay click on its one of 3 things; 1) There is no power going to the relay, 2) The relay is not ground switching on the PCM side, 3) The A/C clutch diode is gone. To check the ground side to the PCM, you can use a test light or create a jumper ground to any metallic part of the body or engine. If the relay switches on with the grounded jumper the problem is with the PCM or the controller.


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## octaneman (May 13, 2009)

Adendum;

Oren,

Since you already swapped relays take your DMM and test the A/C compressor clutch diode first they have a habit of burning out often.


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## oren (Jul 8, 2012)

ok i checked the diode with dmm and getting 13 volts one way and about 4 to 6 volts the other way. Does this mean the diode is bad, and if so what could cause it. I tried it without it in but still nothing.


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## octaneman (May 13, 2009)

Doides are not tested with voltage applied they have to be completly off the circuit to have accurate readings a good diode will conduct only one way.


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## oren (Jul 8, 2012)

ok i rechecked it with the selector on diode (just learning) and it shows .777 and the other way just displays 1. This diode is one that is in the fuse box that you can take out like a fuse. When i probe the slots that the relay plugs in, the 2 at the top looking at the schematic either the one on the left or right will show power on test light when key is turned on How do i tell what the pin numbers are on the relay socket on the schematic. Should i be able to jump from top right slot to bottom right slot and it close the relay switch and provide power to the dark green compressor clutch wire.


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## octaneman (May 13, 2009)

oren said:


> How do i tell what the pin numbers are on the relay socket on the schematic.


There is a schematic diagram printed on the relay with pin numbers on the bottom showing you which pins are the coil's and which is the trigger pin. All you do is orient the pins in relation to the relay's diagram and you will know which pins go where. 

If you jump the top right pin with the bottom right pin on the relay the compressor should turn on.



oren said:


> When i probe the slots that the relay plugs in, the 2 at the top looking at the schematic either the one on the left or right will show power on test light when key is turned on


 On the relay the 2 top pins on the schematic should have power the moment you turn on the key, the issue you are facing is triggering. The relay is not ground switching from the PCM to activate the compressor, you will need to verify the voltages on pins 23, 37, 80 on the PCM's molex connector.


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## octaneman (May 13, 2009)

Oren, 

I'll show you a fast and simple trick on how you can manipulate your relay by applying power or ground. 


Remove your relay from the fuse box and find yourself thin copper wire winding from a transformer or small motor. Take the wire and put a few turns on all 4 of the relay pins (pic 000.) 

When all pins are done put some black tape around the casing to prevent the copper wires from shorting out (pic 001). Insert the relay back into the fuse box slots and now you can test all pins for power, jump to ground , perform continuity test with your meter without the hassle of pulling it out all the time.


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## oren (Jul 8, 2012)

thanks octaneman i appreciate you helping me. I'm beginning to think it may have something to do with the relay socket itself. All the other relays fit in their sockets very tight, but this one for the a/c compressor is very loose. You can just drop it in without having to push it and there is no resistance at all taking it out. It was like this when i bought the car for my son a few months ago. Do you know if the box can be separated to check the receiver slots to see whats going on, it looks like the top part fits into the bottom part somehow but i can't find any clips.


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## octaneman (May 13, 2009)

Loose socket connectors can burn out fuses & relays so it could very well be the problem.
There are two methods that a fuse box is held in place 1) It either has metallic clips that alow it slide in an out or 2) Its seating on a plate thats bolted to the frame of the car.


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## oren (Jul 8, 2012)

i took the air cleaner assembly out that sits directly in front of the fuse box. The fuse box has what looks like a metal track on each side and the box slides back and forth a little, so i guess it is suppose to slide completely out. But it seems that there is a lock of some sort that prevents it from sliding on out, trying to find it. Now if i can get the box out does it separate to where i can look underneath.


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## octaneman (May 13, 2009)

Look at the track carefully on the sides it should have 2 tabs . Push the tabs outward and the box should slide off and you can flip the box over.


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## oren (Jul 8, 2012)

there was a clip under the bottom that locks it on once it slides in on the tracks. Now the problem is how does the box separate so i can see the terminals that the relay plugs into. I can't tell if the box is put together in 2 or 3 parts, hope you or someone can tell me how to do this, i don't want to damage it. Here is a photo of what it looks like.


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## octaneman (May 13, 2009)

GM fuse blocks may come as one unit which may not be serviceable. Some could have tabs which are well hidden or slots which you can insert a small fine screw driver to release the tabs separating the box, unfortunately there are no diagrams in any manuals that will show where they are. If there is nothing on the box which will indicate that it could separate then it doesn't, which means its replaced as one complete unit.


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## oren (Jul 8, 2012)

wonder how hard it would be to find the wires going to that relay and tie on to them and install the relay in a different place. Might be easier than replacing the whole thing, if i can't figure a way to get in it. There are some very small slots on the under side of the lip where the top part sits on the bottom, i tried pushing with a small screwdriver but could'nt tell if anything was moving.


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## octaneman (May 13, 2009)

All you need to do is run an external relay from the main controller by running power connections to the A/C under neath the dash by by-passing the fuse box because the wiring harness are already done for you. Its fast, easy, and allot cheaper than gutting the whole fuse box.


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## oren (Jul 8, 2012)

Octaneman could you possibly get me a drawing or diagram on how to do this, i know it may be simple to you but a little more complicated to me. You say i would use the existing wiring harness, but where would the external relay tie in at. How would i tie in to connections under dash, and which wires? Are you talking about the control head. I just figured if i could get to each wire at the bad relay socket and go from there to new relay, but if the way you are talking about is simpler and easier then i'm all for it...thanks


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## octaneman (May 13, 2009)

Oren,


The diagrams you can find here; AutoZone | Auto Parts & Accessories | Repair Guides & More

What I meant by using the existing harness is you will just cut and re-route wires from broken connections nearest the problem spot without running miles of wires everywhere. 
You could go through the bad relay socket snip the wires from there and connect the relay externally but I do it differently, its realy a matter of personal preference on how you want to have it done. On many models the fuse box is so interconnected it wont give you the leeway to access the power wires underneath the box. Instead of gutting everything what I do is locate on the diagram how the relay is triggered and run power wires jumping from the existing harness to the external relay connecting it with little wire as possible.


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## oren (Jul 8, 2012)

I'll see if i can get to the correct wires, i can get to all the wires going in and out of the box by taking it out so i can get to the ones in the rear. One thing i did today was take the plastic cover off the relay and with the car running and the a/c on i manually pressed the trigger on the relay and the compressor started right up. The only thing is the condenser fan did not come on so i released the trigger. Does this mean its something to do with on the other side of the relay coil,(bad connection at the relay socket, or the pcm,etc.) and would this also keep the coolant fan from coming on.


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## octaneman (May 13, 2009)

Triggering the relay manually is either its not ground switching or the mechanism within the relay is jamming.


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