A/C Gremlin

[rtjohnson1982]

Hey everyone hope you’re keeping the wheels turning, I’m having an ac issue that both my mechanic and I are at a loss with. A/c is going in/out intermittently and the apads system is blinking red 3 times indicating an open wire to the compressor or shorted clutch coil. I’ve cycled the key to reset the system and it will blink green until it decides to act up and go red. We ran straight power to the compressor and it’s engaging, checked freon appears to be good, no obvious sign of broken wires, even installed new blower motor and resistor because the old one was going in/out. Still same problem. I’m starting to think it could be in the clutch coil but didn’t want to tear into it or replace the compressor if that’s not the problem. Compressor was bought new and installed in summer of 2020. Any help or advice is very much appreciated because we’re at a loss and it’s getting hot down here in Charleston,SC!!

[DVT873]

was it built with APADs? Make,Model, VIN would help. Link to some info. https://www.indexsensors.com/uploads/pdf_file.php?id=36 For info search for INDEX APADs. Index controls was who made/makes the system.

[rtjohnson1982]

Yes it does have an APads system and it’s blinking red 3 times which is labeled “open wire to compressor and/or shorted clutch coil”. Truck is 2007 International 9200

[DVT873]

Clutch coil resistance should be 2.8 ohms per a NAv document IK1900018 on APADs troublshooting If less than that APADS reads it as a short. How long does the clutch stay engaed before it kicks out and starts flashing red? Measure the resistance (ohms) cold, then measure it after APADs kicks out. This has a serpintine belt correct?

If the belt is slipping you normally don't hear it. The slippage builds heat on the pulley/coil. This changes the resistence. See this quite a bit on the newer stuff where something electronic is watching how much amperage is going to the AC clutch. Lot of parts get thrown at problem. Often all that is needed is a new belt and tensioner.

If there are any connections in the wire between the clutch and the APADs lmake sure they are tight and clean. Or cut out the connector and splice the wire together.

That little bit of info doesn't seem to show up in the usual troubleshooting info. I learned that in a belt seminar a long time ago. This same slippage will damage front bearings in alternators and cause other heat related damage to them.

Search IK1900018 or try here https://static.nhtsa.gov/odi/tsbs/2015/M...0-9999.pdf Basically same info as APADs doc.

[rtjohnson1982]

Quick update: Traced wiring from APads to compressor and nothing appears damaged. Cleaned the ground connection at the firewall, checked the resistance at the harness coming from coil(3.5 ohms). I don’t know much about electrical so this may not be correct but I back probed the voltage at the harness with the truck running and a/c on and multimeter was reading 64 V which seemed odd to me.Good chance I could have been doing it wrong.
Lol. I can cycle key and reset APads and it’ll blink green, crank the truck and turn ac control on and system will go red within about 20-30 seconds from start. On a run right now but will post a video when I’m back.

[DVT873]

What is the last 8 of your VIN? 64 Volts is probaly not a right reading. The OHM reading is high per the spec. With the VIN I should be able to see if the spec I posted earlier for you is correct.

[rtjohnson1982]

Sure it’s 7C377826