4.3 to 5.3 swap 1999 Silverado AC help
4.3 to 5.3 swap 1999 Silverado AC help 4.3 to 5.3 swap a/c wiring
I?ve got a 1999 Silverado that had a 4.3L and now has been swapped to a 2001 5.3L. The engine, engine harness and computer are from the 2001 Tahoe. Pin 86 is dead(no voltage and not grounded)on the ac relay in the engine wiring junction block(fuse box). However, when I create a ground to the wire that is number 86 on the ac relay,the compressor will come on and work. I know I could just somehow wire me up a ground to that pin but I won?t have any high or low pressure switches to operate the system safely. I guess somehow the high pressure or low pressure cycling switches aren?t letting the relay ground. I?ve tried jumping both high and low cycling switches with a paper clip across the wiring connector and this does nothing. When I jump the high pressure switch with paper clip, I get 3.4 volts to pin 17 ac request wire on pcm red connector. When I jump the low pressure switch with paper clip, pin 55 on PCM red connector grounds. When low pressure is not jumped I get 2.9 volts to one side of low pressure switch. The a/c is set to analog cycling in my hp tuners file.Any help would be greatly appreciated!!
TECH Apprentice
Joined: Aug 2018
Posts: 383
Likes: 108
Looks like he hasn't logged in since 2019, so who knows?
Did you have a question about this?
I also did a 4.3 to 5.3 on my 1999 Silverado. AC works great. I didn't have any issues. Everything is just like factory with the swapped 5.3.