Help! 1995 Base Coupe A/C diode replacement

[john6277]

Maybe I should listen to the "Dutch Uncle" advice of don't fix it if it ain't broke. The A/C works fine. Anyway, I included the A/C diode, connector, and short wire harness unit on my order to Ecklers as a preventative measure. The ad said about 50% of these diodes are bad, and the $20 part is easy to install. Received order and looked for directions, or at least the location of the old diode to replace. Can't find it, and a call to Ecklers was no help as the customer service told me the tech said he had no clue what to do with it and take it all to a A/C repair shop for evaluation.
Does anyone know where to look for this diode ? It has to be near the A/C clutch and compressor. I would like to replace it with the new one or should I just leave well enough alone. Thanks for any info.

 

[ecss]

If you unplug the two pin connector at the AC compressor clutch coil there is a Black wire and a Dark Green wire. The diode is spliced into the harness across these two wires. The service manual doesn't exactly specify where the splice is located. You would have to peel back the convoluted tubing to find it. I'd of thought it would be close to the connector plug. The manual does show an arrow that points to a location between fuel injector plugs 4 and 6.

You can use an ohm meter and verify the diode is good by doing the following.
Disconnect the negative battery terminal.
Unplug the Black connector at the PCM. (There are 4 plugs at the PCM. Red, Black, Clear, Blue).
Disconnect the connector at the AC compressor clutch coil.
Set the meter to Ohms or (diode if the meter has that capability).

Place the Red probe on the Black wire at the disconnected AC compressor clutch connector.
Place the Black probe on the Dark Green wire. You should measure a low resistance in the hundreds of ohms.

Now reverse the probes. Red probe on the Dark Green wire and the Black probe on the Black wire.
You should measure a very high resistance in the mega ohms.

If both tests are correct the diode is good.

Radio Shack sells a 1 amp diode that would work for $1.49 part #276-1102 (!N4003).
Paying Ecklers $20.00 was a ripoff. :L

 

[john6277]

Wow ! Thank you - so simple

Thank you, I did check out the ohm values on the new diode harness first and found similar ohm values on the engine harness connector after disconnectiong the PCM. So all is OK for now and it wasn't an issue after all. I appreciate the help and all the informational diagrams. John

If you unplug the two pin connector at the AC compressor clutch coil there is a Black wire and a Dark Green wire. The diode is spliced into the harness across these two wires. The service manual doesn't exactly specify where the splice is located. You would have to peel back the convoluted tubing to find it. I'd of thought it would be close to the connector plug. The manual does show an arrow that points to a location between fuel injector plugs 4 and 6.

You can use an ohm meter and verify the diode is good by doing the following.
Disconnect the negative battery terminal.
Unplug the Black connector at the PCM. (There are 4 plugs at the PCM. Red, Black, Clear, Blue).
Disconnect the connector at the AC compressor clutch coil.
Set the meter to Ohms or (diode if the meter has that capability).

Place the Red probe on the Black wire at the disconnected AC compressor clutch connector.
Place the Black probe on the Dark Green wire. You should measure a low resistance in the hundreds of ohms.

Now reverse the probes. Red probe on the Dark Green wire and the Black probe on the Black wire.
You should measure a very high resistance in the mega ohms.

If both tests are correct the diode is good.

Radio Shack sells a 1 amp diode that would work for $1.49 part #276-1102 (!N4003).
Paying Ecklers $20.00 was a ripoff. :L

 

[forrest]

If you unplug the two pin connector at the AC compressor clutch coil there is a Black wire and a Dark Green wire. The diode is spliced into the harness across these two wires. The service manual doesn't exactly specify where the splice is located. You would have to peel back the convoluted tubing to find it. I'd of thought it would be close to the connector plug. The manual does show an arrow that points to a location between fuel injector plugs 4 and 6.

You can use an ohm meter and verify the diode is good by doing the following.
Disconnect the negative battery terminal.
Unplug the Black connector at the PCM. (There are 4 plugs at the PCM. Red, Black, Clear, Blue).
Disconnect the connector at the AC compressor clutch coil.
Set the meter to Ohms or (diode if the meter has that capability).

Place the Red probe on the Black wire at the disconnected AC compressor clutch connector.
Place the Black probe on the Dark Green wire. You should measure a low resistance in the hundreds of ohms.

Now reverse the probes. Red probe on the Dark Green wire and the Black probe on the Black wire.
You should measure a very high resistance in the mega ohms.

If both tests are correct the diode is good.

Radio Shack sells a 1 amp diode that would work for $1.49 part #276-1102 (!N4003).
Paying Ecklers $20.00 was a ripoff. :L

Your posting brings up a question that might be key to a mystery, when I bought my car I noticed a wire (definitely not GM) spliced into my a/c compressor clutch. when I called the old owner on it he said that the a/c stopped working and the shop it went to pulled there hair out and replaced the control head and anything else they could think of, and installed the wire I have traced the wire back toward the fire and I loose it. since I don't like this bogus wire and would like my car GM if this diode was bad could this possibly why when jumper is pulled a/c wont run and throws a trouble code on control head.
this was one of those mystery's I was going to pursue when it got cooler, any thoughts?
also 1 other thing and I bet it bogus related no matter what setting I put the climate control to the a/c runs

 

[ecss]

The diode is there to short any voltage to ground when the compressor clutch coil turns off.
Your problem sounds like Bubba couldn't get the clutch to engage so they placed 12 volts on the
AC request line from the HVAC control head.

If the clutch cycles to many times within a give time frame, code 09 Low freon sets and the clutch
will not engage unless you disconnect the negative battery terminal.

First schematic shows the HVAC control head. When ac is requested, 12 volts is placed on the Light Blue
wire that goes to the low pressure cycling switch. If there is at least 47 psi of pressure in the system the switch closes and the the 12 volts passes to the ECM as the AC request signal.

The ECM monitors the high pressure transducer and if the voltage from the transducer is with in the proper
voltage range will ground the AC clutch relay which places 12 volts on the compressor clutch coil.

You could disconnect the unkown wire.
Disconnect the negative battery terminal to clear any codes.
Then verify if the AC works properly.

 

[forrest]

The diode is there to short any voltage to ground when the compressor clutch coil turns off.
Your problem sounds like Bubba couldn't get the clutch to engage so they placed 12 volts on the
AC request line from the HVAC control head.

If the clutch cycles to many times within a give time frame, code 09 Low freon sets and the cliutch
will not engage unless you disconnect the negative battery terminal.

First schematic shows the HVAC control head. When ac is requested, 12 volts is placed on the Light Blue
wire that goes to the low pressure cycling switch. If there is at least 47 psi of pressure in the system closes and the the 12 volts passes to the ECM as the AC request signal.

The ECM monitors the high pressure transducer and if the voltage from the transducer is with in the proper
voltage range will ground the AC clutch relay which places 12 volts on the compressor clutch coil.






You could disconnect the negative battery terminal to reset any codes.
Then remove the extra wire.
See if the AC works properly.

Thanks will give it a try when rain and schedule allows I was planning on giving attention when the heat brakes living in Florida a/c is kind of important, and its working not rite but working

thanks for giving me base direction