I am in the process of finalizing my A/C system on my truck...but am running into some issues. So far I want the LS1 PCM to control the A/C so I get idle bump and fan kick on when A/C is requested. Now is where the problems or questions arise.

I am not using the stock A/C compressor...but instead a Sanden 508 using the S&P high pass mount. Now the LS1 A/C is not a cycling system...it uses a variable clutch or something of the sort. So will the 508 still cycle correctly or not. I could put in the S10 low pressure cycling switch...in line to the A/C relay, to handle the cycling. But then the PCM wont know when the clutch is on so the idle will be bumped and get a high idle situation when the cycle kicks off the compressor. Or I could tie in the S10 cycling switch into the A/C request signal...so that when it cycles the PCM sees the cycling on and off like I am turning the A/C on and off on the dash. But still...what will happen to the cycling of the 508.

Pretty much what I am getting at is will the 508 be affected by the LS1 variable rate system. Or will the cycling be screwed up because it never really turns off the compressor except under load or high RPM. Any help would be appreciated. This is the last step in order to make it all work properly.

Also is it worth it to even worry about the LS1 PCM controlling the A/C system. Cause I could just use the low pressure cycling switch from the S10...and then somehow tie in the fans to turn on when the A/C is requested on the dash (hoping to find a way to do this without throwing SES light from turning on the fans and the PCm seeing this)....the only thing i will lose is the Idle bump...which really seems to me would be liked.

 

I'd leave the ls1 pcm controlling the compressor. You can wire the cycling switch into the a/c request signal from the control panel on the dash. The pcm will then drop idle and turn off the clutch when the lps opens. The logic the pcm uses to cycle the compressor varies depending on what it is flashed for. If the base program is for an fcar or corvette it will need the three wire pressure switch wired into the pcm and the switch installed into the liquid line. A 4cyl s10 has the correct line and switch to make this work. This is the line that runs from the condensor to the evaporator. Then wire in the cycling switch on the accumulator to the a/c request signal going to the pcm from the control panel. The logic in this system lets the compressor run 100% of the time and the compressor then opens up and bypasses internally to prevent damage to the compressor. If it has a truck base program in the pcm then the high and low pressure switches have to be hooked up and wired into the pcm and it will then cycle the compressor correctly.

 

See thats the main issue...I am not using the stock compressor...I am using an aftermarket Sanden 508. So therefore I am not sure if it will still allow the 100% cycle since it does not have the bypass you speak of. It is meant for a cycle based on the pressure switch. On my 4cyl S10 it does not have any sensor in the liquid line (high pressure side) It just goes straight from the condensor to the evaporator, and the only fitting it has is the high side charge port. This is really beginning to confuse me...haha. I should have just notched the frame and kept the stock A/C compressor and not went with the Sanden 508 from S&P. Anyone else have any ideas....and 01WS6/tamu...thanks for the help...maybe I am just not understanding you fully. It seems as though your explanation was for using the stock compressor??

 

If you install the low pressure switch into the a/c request line it will cycle your sanden compressor on and off as needed even though the oem set up for the pressure switch is intended to not let it cycle. Basically it's just like you sitting in the cab and punching the button on and off that is all that the cycling switch you insall will do. What type of vehicle is the o/s for in your pcm. Is it flashed to a car or truck vin. If it is programmed for a car you will have to install the the liquid line from the condensor to the evaporator that has the provision for the three wire pressure switch to enable the pcm to function correctly. You will then install a low pressure switch for a 4.3 v6 s10 onto the accumulator and wire it into the a/c request signal from the a/c control panel. This is completely separate of the 3 wire switch mentioned prior. This will allow your sanden to come on and off as needed using factory pcm controls.

 

Just in time. I'm at this point too on my Blazer with truck computer and AC compressor. Don't know about the Sanden though. On the question of kicking your fans on, somebody on here had a setup where they ran a second wire with a diode in it from the AC on request to their fan relay on control terminal. The diode prevented energizing the AC clutch when the fans came on for temp requirements. I haven't fabbed up hoses yet, but I was planning on running the LP switch in line with the AC on request wire to the AC relay, and putting the HP sensor in the proper place and letting the truck PCM run mine. I think this will work???

 

If the pcm is flashed for a fbody and the 4cyl truck line from the condensor to the evaporator is used with the pressure switch wired in to the pcm. When the pcm receives an a/c request signal it will automatically energize the low speed fans and then monitor the pressure switch if it sees the high side head pressure going up it will then switch the fans to high speed. That is how I am setting mine up.

 

AHHH ok...I see what you mean now. Sorry I guess my head was not all with it last night. My motor is from a 99 fbody and the PCM is also 99Fbody. Yeah I am going to have the high pressure sensor pumbed into my HP line so that the LS1 has the 3wire sensor....and now i understand the cycling switch is what will then control the on off of the compressor. Thanks for all your help...now I just need to find someone who can braze on the SR10 schrader valve...which I believe is M10x1.25 for the sensor....onto my HP hardline. Thanks again for all your help.

 

FYI- The GM compressor is a variable displacement type compressor so it's output is regulated internally without cycling off and on. The system will work by cycling a Sanden, no problem. The three wire pressure sensor is vital to that variable GM compressor.......the sensor provides inputs so the PCM will run the cooling fan as necessary as well as protect the compressor against high or too low pressures.

 

So the PCM doesnt have anything to do with the variable displacement compressor...its all internal to the compressor. The only thing the PCM does is monitor for high/low pressure instance, if seen kicks out the compressor I assume....and turns on the fans when A/C is engaged....thats good to know. So then I will wire in the cycling switch and the 3 wire sensor and have it all function nice like factory. Thanks alot everyone!

 

You can order the line for any 96up s10 with a 4cylinder and the fitting and the switch are already there without having to do any custom welding.

 

Not to sound stupid or anything...but I did not know that the 4cyl trucks used the same sensor as the LS1 does. My sensor for a LS1 only states that is works for an LS1. Does the S10 use the same sensor just on a different threaded schrader valve? I have never seen a 96+ A/C line so I cannot picture in my head what it looks like. All I have ever seen is the 4.3 line which has just a charge port and the 94 4cyl line also just has a charge port. Do you happen to have any pics of the 4cyl line so I can get an idea of what to look at and how to finish up my system. Sorry for sounding stupid...just A/C gets me all confused..haha.

 

On the 2.2 if you are standing by the passenger side fender and looking at the line right after the high side pressure fitting it makes a ninety degree turn straight down. Then about midway down the pressure sensor installs into a fitting that faces toward the front of the truck. It then makes another ninety degree turn at the bottom and hooks up to the evaporator where the orifice tube goes. One thing to remeber with gm is that they change the number and design of everyting to kill interchangability now days. The sensor may be different by how it installs onto the line but the information it relays to the pcm is interpreted the same way. The pcm sends five volts to the sensor and then the varying voltage return back to the pcm is directly proportional to a given pressure at that voltage.

 

This is awesome awesome info. Now all I need to do is find a way to get that line and pressure sensor. So that I can get it into the truck and get this A/C working...its too damn hot in florida. Hopefully all my crazy questions will help some others along the way.

 

Already did, you asked the same questions I was getting ready to ask.

 

Anyone know the part number for that line...dealership looked at me like an idiot and basically blew me off. Kinda urks me...and i cant find anything locally. Would help alot to be able to get this soon...its hot

 

Since I made up my own lines I had to get a fitting with that switch port on it for a beadlock. Tubes & Hoses makes them P/N BL1301-4 for the -6 line or BL1302-4 for -8 line. I have an extra if you have trouble finding one or having one made up.

 

Part numbers are
Line Gm#15034764 43.70
switch#22664328 55.32

Mine is still in the garage waiting for me to finish boxing the frame. I wish the a/c was all I lacked

 

http://www.google.com/url?q=http://w...eWtbzzpbTCf6Ig

 

http://www.google.com/url?q=http://w...kEaaJsL60BTqcA

 

Damm that is cheaper than my wholesale price through the shop. Actually that is even below the factory cost of the part to a dealer. We order through gm spo direct.