2005 lq9 s10 swap AC serial data/request?
07-14-2012, 09:10 PM
#1
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2005 lq9 s10 swap AC serial data/request? I have a 2002 S10 blazer that a squeezed a 2005 HD 6.0 into. Wired to run off my stock fuse block. My compressor won't kick in because the PCM is not getting a serial data reading. How do I get around this without running extra external relays? The fans are PCM controlled as well and will need to come on and have engine idle bumped when ac is turned on. This is my first swap and of all the hours of research I've done I still need an answer. Thank you
07-15-2012, 12:22 AM
#2
We had the same issue on the '86 Chevy pickup we converted with a 2003 5.3 Pullout. The AC request is serial from the HVAC control head. Just hooking up the A/C system without the PCM not knowing produces a lot of undesirable side effects such as surging/dying when the compressor kicks in during certain driving conditions. The PCM needs to know when the compressor is coming on to increase the IAC for th anticipated load. We ran the pickup for a year this way, it was OK but was still 1/2 right.
The other option is to install the AC control head under the dash somewhere and hook it up. This is what we ended up doing. The pickup's control head provides power to the '03 control head under the dash when AC is requested. The head under the dash retains it's last setting, so you don't always have to push the AC button on the head under the dash. Works great, the head requests fans/clutch over the serial network and idle is flawless on transition to clutch engagement.
The tuning software people need to get this addressed, it shure would be nice to have an enabler box in the tune like for electric fans.
The other option is to switch back to a '99-02 PCM, which uses a ground input to enable the clutch from the A/C head unit, and is hardwired to the head unit, instead of the serial network like on '03 and newer.
The other option is to install the AC control head under the dash somewhere and hook it up. This is what we ended up doing. The pickup's control head provides power to the '03 control head under the dash when AC is requested. The head under the dash retains it's last setting, so you don't always have to push the AC button on the head under the dash. Works great, the head requests fans/clutch over the serial network and idle is flawless on transition to clutch engagement.
The tuning software people need to get this addressed, it shure would be nice to have an enabler box in the tune like for electric fans.
The other option is to switch back to a '99-02 PCM, which uses a ground input to enable the clutch from the A/C head unit, and is hardwired to the head unit, instead of the serial network like on '03 and newer.
07-15-2012, 10:36 PM
#4
If you reworked the harness properly, maybe, but i'm not sure as I haven't studied the wiring diagrams enough to be able to call out the differences.
The best bet for the A/C fix is to go with the '02 and older PCM, but again I haven't tried this method either. I recently did Efans on my '99 Silverado and got some experience with the A/C request by messing with it. I found that the A/C control head supplies ground to the ECU, when the ground is removed the A/C clutch is requested. However, Idk if the older ECU's (99-02) can run DBW.
This was our dilemma as well, we didn't want to change the pickup over to cable throttle, just for the A/C fix, and found that it was easier to get a control head from an '03 and newer, wire it into the network and stuff it under the dash. I powered it off of the pickups existing control head so that when the selector is in any position that requests A/C it provides ignition power to the dummy head under the dash, and in turn requests the A/C clutch via Serial Network.
Seems to work great so far.
The best bet for the A/C fix is to go with the '02 and older PCM, but again I haven't tried this method either. I recently did Efans on my '99 Silverado and got some experience with the A/C request by messing with it. I found that the A/C control head supplies ground to the ECU, when the ground is removed the A/C clutch is requested. However, Idk if the older ECU's (99-02) can run DBW.
This was our dilemma as well, we didn't want to change the pickup over to cable throttle, just for the A/C fix, and found that it was easier to get a control head from an '03 and newer, wire it into the network and stuff it under the dash. I powered it off of the pickups existing control head so that when the selector is in any position that requests A/C it provides ignition power to the dummy head under the dash, and in turn requests the A/C clutch via Serial Network.
Seems to work great so far.
