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Saturn AC clutch problem

rh on Thu August 26, 2010 5:05 PM User is offline

Year: 2003
Make: Saturn
Model: Ion
Engine Size: 2.2
Refrigerant Type: 134
Country of Origin: United States

Hello to all.

I'm having a problem on my 2003 Saturn Ion 2.2 L, blowing the AC clutch. Started old compressor went bad, froze up, I replaced the compressor and clutch with a new unit, the condenser & drier, expansion valve, inline filter, flushed the system added PAG 46 oil and charged to spec. and turned the compressor over by hand 20 times. I started the engine and pushed the AC command nothing, checked the fuse it was blown, installed another it blew as soon as ac was turned on. I tested the system out have 14.2 volts at connector engine running, no shorts in wiring, relay is good. Diode is good. tested clutch coil 0.2 ohms shorted out. Sent back and got another one and as soon as AC was turned on fuse blew again coil was shorted 0.1 oms, I took my old compressor and hooked up the connector to the clutch leaving the replacement hooked up to the engine, turned on AC and it was ok did not blow fuse and clutch would engage.
Called back where i bought it from now they think i'm nuts, sent back the second one had them test the next one before shipping, and I tested it as soon as it came 3.8 ohms the same as the one that came on the car. I installed this one and as soon as power was applied the fuse blew, tested coil and its .01 ohms again shorted. The compressor shafts all turn free by hand, none of the compressors have ever engaged because the fuse 10 amp has always blown in less then a second. I have tested and retested every thing in the system that I can think of and remember if I hook up the O.E. compressor I do not have the problem. I have noticed on the web site of the place I bought it all from the compressor the sell for the Ion is not a direct replacement but listed for other GM with the 2.2 ecotec motor, 2004 and up chevy malibu, and others, it fits fine but could there be a difference in the coils, or am I just missing something.
I know this was long winded please forgive that and if anyone can help before I pull all my hair out?

Thanks much
Robert

GM Tech on Thu August 26, 2010 5:48 PM User is offline

The coil on your replacement compressors has a built in diode-- it is polarity sensitive-- look really close at the base of connector on coil, there will be a + and a - negative sign. There-in lies your problem, your system is wired the opposite of the coil-- so once you confirm all this, you must reverse the wiring polarity in your harness plug. 2003 was a changover year, they could use both a delphi 6CVC and/or a competitor compressor-- I know for a fact if the coil base of the Delphi unit is black-- it has an embedded diode built in the coil of which you are shorting out by applying reverse polarity. Yes it is an application issue, but coils with embedded diodes are now polarity sensitive and cannot be wired in either direction. If it were me, I'd cut the harness wires and reverse the polarity- you presently have two diodes in the system fighting each other,,,, otherwise....they need to work together i the same direction.

Also your resistance check should prove the diode is in the coil- since you can only read resistance in one direction on a new coil- did you not see that when you did yor coil resistance checking? Reverse the leads and see if this holds true...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Thu August 26, 2010 at 11:11 PM by GM Tech

rh on Thu August 26, 2010 10:50 PM User is offline

jglanham on Fri August 27, 2010 2:34 AM User is offline

I agree that if the new clutch has a built in diode and reverse polarity voltage is applied, the diode will conduct and blow the fuse. The diode has a 50/50 chance of blowing wide open or melting internally creating a permanent short. In your case, it seems to be shorting.

GM Tech:

Quote
Also your resistance check should prove the diode is in the coil- since you can only read resistance in one direction on a new coil- did you not see that when you did your coil resistance checking? Reverse the leads and see if this holds true...

That would hold true only if the diode were wired in series with the coil. However, most coils have the diode wired in parallel with the coil and are reversed biased. The diode conducts only when the coil is de-energized, creating a short circuit, so that the current produced by the collapsing magnetic field of the coil circulates within the coil and not back to the relay contacts. If it did not have the diode, the high energy pulses from the coil would rapidly destroy the relay contacts due to excessive arcing.
An ohmmeter is a high impedance device and cannot source enough current to forward bias the diode when measuring across a low resistance coil. It will only display the resistance of the coil. Automotive coils, ie: A/C clutches, fan motors etc. normally have diodes that are rated at 1 amp or above. A simple way to determine if a device has a diode across it and to determine the polarity is this:

Connect test clip leads on the coil. Connect one lead to the common terminal of a digital multimeter. Set the multimeter to read amps. Some meters require moving the positive lead to a separate terminal. Take a AAA alkaline battery and connect one end to the positive lead of the meter. Take the other clip lead from the coil and touch the other end of the AAA battery just long enough to take a reading. Record the reading. Reverse the battery and record the reading. One reading will be lower than the other. The low reading indicates the diode is not conducting. This is the way you want it connected in the system.
When the battery is connected to give the low reading, the coil lead that is connected to the + end is the + terminal for the coil.

Don't try this with a larger battery. The reason this test works is that the AAA battery has enough current to cause the diode to conduct, but not blow.

If the readings are the same when conducting the test on an unknown coil, then the coil doesn't have a diode across it.



-------------------------
johnl

Edited: Fri August 27, 2010 at 2:40 AM by jglanham

rh on Fri August 27, 2010 3:56 AM User is offline

rh on Fri August 27, 2010 4:39 AM User is offline

OK

Thanks for all the information and education, let me see if I understand the original clutch does not have an internal diode built in the coil but an external one in the fuse box, the replacement one has a diode built into the coil that is polarity sensitive? I did look at both coil connectors the original Delphi has a black base the replacement has a white base but the positive and negative on both are the same. Would that mean the diode was installed wrong in all the replacements? The connector terminal with voltage should go to the positive mark on the coil right? Also I did not full understand the test with the AAA battery does the black lead from the meter common go on the negative terminal of the coil and stay there through the test and the red lead to the AMP input go to one end of the battery and another lead from the other end of the battery to the connector positive and i'm lost, sorry.

GM Tech on Fri August 27, 2010 8:31 AM User is offline

What comressor was on the car the day it was brand new? I assume it was a not a Delphi unit-- the Delphi CVC became OEM later in 2006 or so-- but it canreplace the OEM pump--except that Delphi units have embedded diodes-- and need to be wired appropriately...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Fri August 27, 2010 9:15 AM User is offline

Is the polarity from the car matching the + and - marked on the coil? Sounds like it is not.

Instead of a AAA battery I'd suggest a car battery with a bulb wired in series as a current-limited test source. For example a #1156 bulb is about 2 amps. If you have a smaller bulb use it instead for less risk of damaging the diode, though really small bulbs won't flow enough current to make the test work. Connect the battery, bulb, and coil all in series. With the coil the right way, the bulb will light dimly and a few volts will appear across the coil. Wired the wrong way, the diode in the coil will conduct, causing the bulb to light brightly and less than 1 volt across the coil.

Edited: Fri August 27, 2010 at 9:17 AM by mk378

jglanham on Fri August 27, 2010 4:38 PM User is offline

A light bulb with the car battery will work, however, I would suggest using a bulb that draws less than 1 amp to be on the safe side. Reason being, just because the coil draws 3 amps to operate, the diode doesn't have to be rated for 3 amps. A 1 amp diode is usually sufficient. Cost is everything to OEM's.
To answer your question about the AAA battery test, You are connecting a AAA battery across the coil, but are using an ammeter in series with the battery to give the indication instead of a light bulb. The leads stay connected to the coil and the ammeter. You just reverse the connections to the battery.

(+)-------coil------ammeter or bulb-----------(-) Circuit one-- Battery polarity connected one way.

(-)--------coil------ammeter or bulb-----------(+) Circuit two--Battery polarity reversed.

The correct polarity of the coil will be the same as the polarity of the battery in whichever circuit causes the bulb to be dim or the ammeter to read low.

As a side note, it doesn't matter if there are two diodes in the circuit (one at the fuse box, the other in the coil) as long as they are connected in the same polarity.

Also, if the vendor won't allow you to return the clutch, you can try to blow open the diode in the coil. You can do this by applying full battery voltage (12v)across the coil (without a fuse in the circuit). Use heavy gauge wire jumpers clipped directly to the battery. Be sure to wear safety glasses or goggles and heavy gloves when performing this procedure. Connect one jumper to one lead of the coil, then very quickly touch and release the other jumper to the remaining coil wire. You may have to repeat this procedure several times. If the clutch pulls in, you have been successful. Be careful not to hold the lead on too long (a fraction of a second is what you want) or you will melt or even weld the wires if the diode refuses to clear. You may or may not hear a loud "pop" when the diode blows. Most of the diodes in the coils are in plastic packages and literally explode when "zapped".

Hope this helps.

-------------------------
johnl

Edited: Fri August 27, 2010 at 6:23 PM by jglanham

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