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post #1 of (permalink) Old 10-02-2015, 12:56 PM Thread Starter
LiveToDrive
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Join Date: Nov 2012
Location: Alta Loma, CA
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A/C Troubleshooting Saga (2007 Elise)

I've got posts all over the place in this section and I wanted to compile all of my progress in one place. I hope that someday, someone will be able to recognize these symptoms and finally help me solve this riddle. Here go's:

2007 Lotus Elise SC complete A/C diagnostic and repair history notes.

After purchasing the vehicle from the previous owner it was discovered that the AC was not blowing cold. On two occasions I was able to get cold air by cycling the AC blower off and on repeatedly. This no longer works. The blower works properly and the heater works properly. Also, the AC light on the button turns on when pressed and the engine RPM raises as it should. I watched the AC compressor with a flashlight as someone turned the AC on and off and I discovered that the clutch was not engaging, or was engaging very softly as if the clutch was possible worn or broken.

I called the previous owner to discuss troubleshooting history. I was told that the car was taken to the Lotus dealer for AC repair and the dealer discovered a "bad ground" near the compressor in the engine bay. The ground was fixed, but the AC still did not work. The next step was to remove the front clam and inspect wiring, but the previous owner declined this work.

After researching countless forum threads on the topic I began troubleshooting the AC system myself. These are the efforts that have been made to this point, with mixed success:

1. Hot/cool air flap tested and found to be functioning properly. The blower duct was removed and I visually confirmed the flap moved when the thermostat was rotated inside the car.

2. Temperature probe was found to be poking into the condenser fins. I pulled the probe just slightly away from the condenser fins.

3. Wiring to the Trinary switch was inspected as far as I could see and looked ok. Connectors to the Trinary switch were cleaned and inspected. All seems OK, however I could not inspect all of the wiring with the front clam in place. Subsequent cleaning of these connectors seemed to resolve the issue, but it was a false alarm. The issue came back shortly thereafter.

4. AC main relay (on front passenger wheel liner) was replaced with a used unit. This did not resolve the problem so I re-installed the original relay.

5. The AC compressor relay fuse was inspected (front fuse box). The AC compressor fuse was inspected (under dashboard). The ECU fuse (R4, engine bay) was pulled for 10 minutes and replaced.

6. I attached a pressure gauge to the low side refrigerant port and found the system was charged to way over 100 psi. I relieved the pressure down to 40 psi. No change. I then relieved 100% of the refrigerant and re-charged with an off the shelf r134 to 50 psi.

7. The discovery of extreme pressure on the low side port led me to believe possible AC compressor damage had occurred. I replaced the AC compressor with a new unit designed for an '05-'09 Toyota MR2 Sypder. I had to re-use the wire harness off of the old compressor as the new harness would not reach the plug.

8. I had the AC system professionally recharged, filling it with 1.25 lbs of refrigerant.

9. I disconnected the vehicle battery for over 2 hours and reconnected in hopes the ECU would re-learn the refrigerant pressure and activate the AC. Upon restart the compressor would not kick on, but on a subsequent restart the compressor DID kick on and the air got cold. Unfortunately, on the following restart it did not work.

Current status is the AC now works intermittently. If the car starts and the AC works, then it stays working. If the car starts and the AC does NOT work, then it will not work until a successful restart of the engine. I'm trying to determine if there is a relation between engine operating temperature and working AC. It appears that the compressor will kick on once the engine is warmed up, but it's not 100% consistent.

Other theories:
1. Bad ecu. I also have an airbag light on the dashboard. Perhaps this is related.
2. Bad wiring. Perhaps there is a wire with too much resistance or it is grounding somewhere.
3. Bad temperature probe.
4. Bad trinary switch.
5. Both my current AC relay and the used relay I tested are bad.
6. Bad thermostat.

Important note: This vehicle did not come with the factory supercharger. It was installed by the previous owner. I imagine the AC issue came about after the supercharger was installed. There must be some connection to the supercharger, perhaps in the ECU software that is causing this.
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