mr03silverado

The fans come on at 196 deg, but as I've seen others say, when at a stop the AC blows warm because no fan is on (2003 5.3l 1500) if the truck is not up to 196 yet. The harness seller says that the AC pressure switch needs to be set up on the PCM tune. The Diablo tuner guy says that there is not a AC pressure switch setting.

Can anyone lead me in the right direction? The tuner says that he's never had a problem with this on the numerous tunes that he's done before.

zblee

There are two settings for the fans to turn on. Fan 1 setting and Fan 2 setting. Fan 1 setting has lower temps and lower AC pressure. Fan 1 trigger puts the fan on low. Fan 2 settings have higher temps and higher AC pressure. Fan 2 trigger puts the fans on High. but this also depends on what relay setup you have. I have a 3 relay, so when fan 1 (the trigger for lower temps and lower ac pressure) gets triggered it sends power in series to both fans so each fan gets half the power ( low speed ) . When Fan 2 get triggered it sends power to both fans so both fans get full power ( high speed).

On the fan 1 settings in the PCM there is also a trigger ( other than ac pressure and engine temp) for minimum speed to disable. If this is set at 45mph , your fan will shut off if you travelling greater than 45mph.

So there are 3 items in the tune that need to be adjusted, its either the temp ( sounds like you have this already), the AC pressure or the min speed disable. since you have temp set and you get no fans when AC is on, either the pressure numbers need to get adjusted or the min speed needs to get adjusted...


I just did this swap on my 2003 5.3l a couple of weekends ago. let me know if you have more questions. I am using HPTuners

01SilveradoJakee

What harness did you use? I used PCM of NC harness Great quality! Anyways I weird it in direct with my ac compressor. I drove my truck a whole day with just my ac on and as long and the truck commanded the ac clutch on 1 fan was on low so it never overheated. Now it's a full tune, 1 fan is on with my ac until 35 mph. 2 fans on low are on at 195* and / Fans on high at anything 210 or more

Shtbox

I used the Nelson performance e fan harness and there was a green wire that you have to connect in the harness when the a/c is on well when I hooked up the green wire my a/c stopped blowing cold so I disconnected that green wire and the ac started working again.

wuznme

iTrader: (2)

There are 2 settings for the AC pressure switch, 210psi and 310psi