Installing AC High Pressure Sensor on 99-02 Silverado

[Jason B]

Yes, the '02 silverado uses a low pressure cutout to cycle the compressor, maybe it's formally called a compressor cycling switch. And it has a high pressure cutout switch. These are just on/off.

My truck is a '99 s10 with a 2007 5.3 and a 2002 silverado calibration in the pcm. The fans turn on and off fine by engine temp as stock as it gets having been converted. Now adding a/c adds a ton of confusion to it because the pcm wants to see pressure. I've noticed on my camaros that the low fan is almost always on with the a/c and the high fan kicks on and off frequently.

I live in Florida and built this truck without a/c during the cooler months and when summer came I hardly drove it because it was so hot out. I put a/c in it.

I tried the transducer but I already had my fans set up to run second stage only, meaning once the a/c runs a minute or two the fans come on high speed, so not wanting to rewire my fans I just added a relay activated by the a/c request wire. This relay grounds the main fan relay when the a/c comes on. The reason I did this is because I didn't think my fans would keep up with it all. I had the stock thermostat at first and it would run at 205 degrees, so once it got heated up the fans would run all the time anyway.

Now I have a 160 degree thermostat and my fan settings are on at 192, off at 190, and they actually cycle. So with this thermostat and the fans actually cycling I have put wiring the a/c fans through the pressure transducer on my to do one day list also.

[ryeguy2006a]

You don't have to change the OS, the older OS will still control the fans, and I have not verified, but should interpret the High pressure value. I currently have a 2002 Silverado running the factory OS controlling my fans just fine. I also have a 98 suburban running an 0411 running electric fans with a completely different OS.

The advantage of using the PCM to control the fans via the pressure switch vs the A/C relay is that the PCM turns the fans off when you reach a designated speed. There is no reason to have the fans running when the vehicle is traveling at 45+ mph. I personally believe it would actually cause a restriction instead of allowing the fans to free spin at those speeds.

Jason, keep in mind I'm not trying to argue with you, I'm just explaining my thought process and experiences. I did miss your comment when you replied to the need to run an 05 OS, which I agree you most cannot run a 05 OS on a 02 PCM. I am pretty sure you can go the other way around, but that isn't the point right now...

53Bowtie, the reason you can't use the later OS is because it needs the 1mb PCM which is the blue and green vs the 512kb PCM which is the blue and red that you have.

Hi guys,

I'm working through a similar issue on my LS swapped OBS Silverado. I'm running a 2002 Silverado 0411 PCM, and the motor is a 06 LQ9. I recently swapped the truck over from a clutch fan to the 05+ Silverado cooling fans and I'm searching for the best way to wire up the truck.

I'm looking to do this exact thing described above by Markmx6. So, if I'm understanding this correctly I would need to tap into the High pressure cut off signal on my truck, and connect it to the C2-14 pin? And as for the tune on the truck, do I simply update from A/C recirculate to 2 Fans or is there a table for the A/C pressure settings? Also, do you happen to have a wiring diagram that you used for the cooling fans? Did you use a single fan or the dual cooling units?

Sorry for the specific questions, but I'm not very familiar with A/C systems and this is exactly how I want to have the PCM control my fans.

[orange ss]

need to do a system segment swap to utilize the a/c pressure transducer function

[2xLS1]

https://www.performancetrucks.net/fo...ontrol-553385/

[[email protected]]

hey guys, maybe someone can help me with my operation of my fans. i have an 02 silverado, 34" radiator, dual fans, installed bp e fan harness and the transducer to act like the 05-07 chevy, my problem is when at hywy speeds, mine freezes up. below 45 mph and in town driving everything works fine. #fan 2 is on recirc and I've tried the analog, analog cycling, serial, serial cycling and it still freezes at hywy speeds only. I'm wondering if the transducer can't be used on a truck that has no auto ac controls. could a different control head be used that has auto ac?