I did. That is just a high pressure cutout for when the AC pressure gets too high and is supposed to kick the compressor clutch out before the high pressure pop off valve opens in the compressor. The high pressure cut out switch is a normally closed switch so its really got nothing to do with the fan operation.

The HVAC compressor control schematic for a 99-02 shows it having or at least some models having a AC high pressure recirculation pressure switch but I have no idea where it is, if it even has it, and what it was intended to do. My only thoughts is it somehow sense high pressure and turns would have turned the AC recirculate on which would send already cooled air across the evaporator which would decrease the amount of heat being put into the system which in turn would bring the high side pressure down but at the same time I don't see how this would have anything to do with the fans coming on at 350 psi like they are now and otherwise seemingly being controlled correctly. On my 99 it did have the auto recirculate wire pinned in cavity 33 which I unpinned and pinned the fan harness high speed control in there. I don't get it.

 

https://www.performancetrucks.net/fo...1&postcount=22

https://www.performancetrucks.net/fo...2&postcount=25

I remembered the pressure wrong for the A/C recirculation switch.

 

So the recirculation switch is what is turning my fans on low speed for AC operation. That makes sense. Whats weird is in stock form that switch would produce a signal to the PCM which in turn the PCM would produce an output at C2 pin 33 based on the recirculation switch input. As it sits now it seems as though the output from the recirc. switches input is coming out of the PCM at C1 pin 42 IE low speed operation. To me it seems like ideally you would have an AC request signal ground C1 pin 42 to turn the low speed fans on and then have the AC recirculate switch do its normal job is producing an input to make an output at C2 pin 33. Doing this should produce a normal low/high speed fan operation based on coolant temp as well as low speed fans on with an AC request and high speed fans on above 350 psi. The question is how to accomplish this? I could leave it alone as its working ok but its not working correctly IMO. Unless I'm seeing this wrong there is currently no high speed fan operation for the AC system, only for the cooling system.

 

Pin 33 is high speed fan control. If your low fans are coming on when pin 33 supplies ground, then your fans are wired wrong.

 

I know it is. My fans are wired correctly. What I'm saying is that somehow efi live has rerouted output of the recirculate pressure switches input to pin 42, IE low speed fans. What I'm saying is that for the 99-02s they need to have it setup so that anytime there is an AC request the low speed fans come on via grounding pin 42 and that when the pressure reaches 350 psi the high speed fans come on via grounding pin 33. To do this the input from the recirculate pressure switch would need to be setup to produce an output on pin 33 as it does in stock form to operate the recirculate door. All this could be done with programming but I'm not sure how to do this with EFI live. If it was OBD1 and tunerpro sure I could figure it out but I'm new to code changes with EFI live.

 

I know EFI live has had problems with controlling efans incorrectly. You may want to try lowering you Fan #1 AC on temp and see what that does for you.

 

Its not the temperature based controls that is the problem. That works both high and low, I've tested it.

Adding to my above post to further make this as correct as possible you would want your AC request signal for low speed fans to come from C2 17 which is the AC request signal from the HVAC control head. If you just tied into the AC clutch circuit like many do this would cause unnecessary cycling of the fans each time the clutch cycles. Using the AC request from the HVAC control head would mean anytime the AC button has been pushed and turned on the fans would be on low even if the compressor is cycling. I may have to contact efi live. They are going to hate me.

 

No. I want you to lower your {G0903}Fan #1 Turn On by A/C Temp. The 99-02 trucks do not have an A/C pressure sensor that measures variable A/C pressure. So what you need to do is use a coolant temp that will cause the low fans to come on when the A/C is turned on. The condenser adds heat to the cooling system. So turning on the fan when a/c is on will help cool everything off and drop pressures some.

The way your tuned now, your fans won't turn on until the coolant temp is 220* or your pressure gets high enough to trigger the high fan for a/c. If your coolant temp gets to 204*, they come on whether the a/c is on or not. You want them to come on earlier when the a/c is on.

 

I smell what you're stepping in. If I set G0903 to something low like 50 degrees anytime there is an AC request with a coolant temp of 50 or more the low speed fans would come on regardless of what the recirculate pressure switch it at. That would work, not ideally but it would work. The reason for 50 degrees would be for a cold start. 50 would really be lower than needed but there are a lot of times when its in the 60s I would want the AC on immediately after a cold start so I would want them coming on.

Actually what might be easier would be to use a 03+ cable driven operating system and add the necessary wires and a variable AC pressure sensor.

 

The problem with the 03+ setup is you need a new PCM and would need to rewire both connectors as most of the wiring changes.