Russ Stein

I want to close this thread as now fixed. Referring back to my post of July 2nd and my suspicion that this vehicle had sustained a voltage surge via jump starting from a running vehicle; this is confirmed by the attached image of the ecu’s charring adjacent to the hi-amp cable attach points. Fitting a new ECU-compressor immediately gave me functional A/C.

Jonny, From this DIAG stream do you see a clue as still no compressor function? This one is being a bit stubborn!

Here is a trace in DIAG mode, engine at idle, blower in the car at half speed, condenser fan on, compressor still not on.. Trace taken after idling about 10-15 minutes. Blue LED bright blue, orange and red leads to compressor reading 12.52 volts; as noted I merged red and yellow to deliver 12v to the orange lead. I think I stated that the contractor is deleted on this installation.

Jonny, After some delay, back on task. Still no compressor, but more information. Updated firmware from 12.6 to 1.15, verified compressor brand as Benling, verified compressor as running on 12V (third line list text reads INV Normal [0]. Then checked ECU to compressor harness; all female connectors passed the resistor wire test (tight!). All four leads tested correctly per your “More advice on diagnosing a non-starting compressor” post. I thought I had it nailed when my ECU output for the yellow “enable” lead was 4.96V. But, upping to 12V (bridged from the red 12V lead) made no difference when the CMP=50 command was given. I personally suspect a compressor at this point as my ECU will not accept the 17.1 update plus I suspect this car may have been jumped from a running vehicle many times by its previous owner knowing the circumstances of its ownership. ECU’s do not take kindly to such current surges. Comments?

By the way, the manuals-and-software link you referred to does not have and firmware zip files that I could find on anywhere at that location. But, then I've not always been the sharpest knife in the kitchen...

Yes, the circular blue LED around the button illuminates at the low level on the car's starting, and then brightly when button is depressed and the blower fan is on (via the OE slide control), and of course the condenser blower fan is running as well. One can run the vehicle for an extended period (idle or driving), but still no compressor operation, hence no "cold" air output, only ambient. Our current temps here run about 30-32 degrees C. The vehicle is currently fitted with a 120 amp alternator and idles at 1000 rpm, so I feel the ECU is never seeing a low amp condition; voltage is always showing 12.5 at the battery.

I recently acquired a LHD 1987 911 with a single condenser Electrocooler system fitted. My issue is that the compressor will not cycle on at all. We have verified a correct installation of the system, pin-out tested all wiring against the installation manual, and seen that we have 80 psi static pressure in the system as well. We also have bypassed the contactor (temporarily) so as to assure correct amperage to the compressor. Everything is working except the compressor. Now we need to talk to the ECU to find out what is going on, but at this point can't talk to it. Serial drivers load automatically to our Lenovo PC fine when the supplied USB cable is plugged into the PC, but there is no response when the cable is plugged into the ECU. Apparently we must have the firmware (zip file) to load the puTTy utility program,, but the website in the manual referred to as a source for the zip is now non-existent?. Can you help with a source for the needed firmware file? Thanks in Advance!