I hate to have to bother anyone with this, as, at this point, it’s not a huge issue anymore. That said, I’ve invested enough time on this that the one remaining issue still bugs me so I wanted to at least post to see if anyone could spot a careless error / assumption on my end.
Preface:
I’ve been working on a e-fan install for a 02 Silverado 4.8L Vortec with P01 PCM Running OS 12212156, but have run into a handful of issues. Thankfully, during the time it took to register + get approved to join this forum, I’ve debugged nearly everything (all software / calibration related) with logs.
Setup:
Series / Parallel relay setup + AC High Pressure Sensor feedback circuit
Modified AC request wire to run through the AC system’s low pressure sensor, so that my AC compressor would cycle properly
Coding:
I’m working with a OBDX Pro VX using PCMHammer/Logger, LSDroid, and Universal Patcher.
My process was to compare against a 05+ Silverado that came with stock efans and change my tune to reflect the changes related to AC and fan control. The only things specific to my install that multiple tutorials online didn’t cover is that I had to change my AC System Type to #2 / Analog (Non-PPEI_V7) to go with my ac compressor that uses pressure switches to ‘cycle’ the compressor via the AC request wiring + enable the 3-wire analog high pressure sensor I’ve added. This had to be done since the stock setting was #3 / Analog Cycling (Non_PPEI_Cycling) which looks for the low pressure switch on C2 #55 which fails because it isn’t connected anymore (see this)
Current State:
Good:
Both series and parallel modes respond properly to the fan1 and fan2 ECT setpoints defined in my modified bin (using Universal Patcher).
AC modified AC request with high and low pressure sensors verified to work properly
AC high pressure sensor feedback verified and tracks with high and low pressure switches above.
Bad:
Fans do not seem to respond to AC pressure feedback. Specifically, when the AC is commanded on and the compressor turns on, the pressure builds on the high side, and the condenser heats up as pressure continues to build, but the fans never come on. This continues until the AC pressure sensor gets to ~5V / 450PSI and the high pressure limit switch interrupts the AC request, cycling the compressor.
The fans lack of response to the AC pressure is the reason for this post.
These are the related calibration parameters from my tune (ECT setpoint temps are very low for testing):
Also, my bin is available here for a full overview:
As I understand it, I should get series fan (low speed) operation / fan1 when:
AC_Pressure_Fan1_High_Threshold > 219 PSI
AND
ECT_Fan1_AC_On_Threshold > 40C
AND
Vehicle_Speed_High_AC_fan1_Th < 30MPH
However, when I try it parked in my garage, I don’t get a fan-on trigger:
The graph above is a little dense, but here’s how I read it.
When ECT is ~44 degrees, I request AC which turns on my compressor. The high side starts building pressure and I can feel the condenser heating up. This continues to happen until I almost hit ~5V / 450 psi (which is where my high pressure limit switch normally steps in and cycles the compressor (demonstrated multiple times while debugging this issue), but is saved due to the ECT hitting ~66C and activating low speed fan operation which removes the heat and pressure from the AC system through the condenser which you can see by the quick voltage drop coming from the ac pressure sensor. The drop continues until the low pressure ac switch cycles the compressor periodically which is expected behavior. Finally, you see the high speed fan operation kicking in at ~73C ECT. After that, I stop the logs.
My question is mainly related to the ECT_Fan1_AC_On_Threshold variable, as I expect that’s where I’m making assumptions. To me, setting the threshold at 40C means this test should have worked and I should have gotten low speed fans when my AC pressure was > 219 PSI because my ECTs were > 40C and I was parked for this entire test.
That’s assuming there aren’t any other conditions / prerequisites I don’t know about. Does anyone out there know of any? Can you spot any other problems with my tune or assumptions I might be making?
Since I wrote up this question, I have tried the above test multiple times. Each time, I do a full warm up, park my truck in the garage and repeat the test. ECTs are usually around 90C, MPH = 0, and I get a full 0-5V ramp on AC pressure feedback but no e-fan turn on.
I’ve also tried changing Type_Of_AC_On_Vehicle to 1 / serial cycling (PPEI_Cycling) and ECT_Fan1_AC_On_Threshold = 10C and neither improved the situation. I can also post these logs if it would clarify anything.
In closing, I know this really is a low priority problem to troubleshoot as the only time I’d ever see this exact scenario is if I started my truck in hotter weather and just ran the AC for 10 minutes at idle. In which case, the AC would still kind of work, but it would be high pressure and would be hitting the high limit switch multiple times before the coolant temps came up high enough to kick on the fans at normal operating temps. Despite the insignificance of this issue, I’d love to get it sorted out before I completely close the lid on this project as I live in the deep south and AC is definitely something I’d like to get sorted 100% before next summer.
Any help is greatly appreciated.
Lane
