Quote:
Originally Posted by rocketmench
Hi all, I realize this is an older thread, but I thought I'd post an update regarding how those 2003+ Blue/Green P59 PCMs that do not accept analog 12V signal for A/C request can be modified to accept that signal. I'm going to be restoring a 1968 K20 and I want to have analog A/C with my LS swap also.
In summary, I obtained two PCM's to compare; one that had the IAC stepper control mosfets and A/C request circuitry, and one that did not. I traced out the circuit at pin C2 17, where the A/C request signal is sent. On the PCM that can accept this signal, there is a pull-down resistor and debounce (low-pass filter) resister/capacitor combo that is missing in non analog A/C request PCMs. I verified that when these components are soldered into the board, the PCM responds to analog A/C request. And fans 1 and 2 can be made to come on as well if using the Analog mode in the OS.
I posted the details of which resistors and capacitors to add in a post over at ls1tech.com:
https://ls1tech.com/forums/conversio...c-request.html
Hope this helps. |
I just read your thread on LS1Tech, and I'll give credit where credit is due, that's pretty impressive. You are obviously more of an electrical engineer than I am, because there's no way I would have ever figured that out. I think the downside is that most people without your knowledge and soldering capabilities will do more damage to their PCM than good trying to add those small parts.
So did you still have to change the A/C request to 'analog cycling' in the tune? I assume that's what you used the Tunerpro for?
I'm not knocking your work, but it still is probably still a little easier for most people to just find a PCM with IAC drivers and just reprogram that to make it work if PCM controlled A/C is a must for them.