Cant get high fan with a/c

[lowws6]

I have done a 411 PCM swat to my 96 gmc, installed e-fans with two speed control. I want the fans to come on high when my a/c is on because my high side pressure is about 250psi. I have done everything I can but get no response. I wired 5volts to the a/c pressure sensor circuit and changed G0918 to 1kpa and G0919 to 0kpa. I am thinking the PCM does not support this option.

[lowws6]

All the 411 conversions here and nobody knows anything about this? Come on dont tell me I stumped the efilive forum.

[5.7ute]

Have a look at this thread. It appears that the early pcm's dont support the 2 speed function & you need to trigger the fans from the A/C.
http://forum.efilive.com/showthread.php?t=12607&highlight=efans&page=2

[lowws6]

The two speed fans are working fine, its just the a/c trigger portion thats not working.

[ChipsByAl]

Are you using the 02 Express Van file for your base tune?
Al

[lowws6]

Yes, 02 express

[ChipsByAl]

Compare what you have wired to this Camaro circuit.

[lowws6]

I have everything except the pressure sensor. I have put 4 volts at C2 14 to get the ecu to think there is a switch there and still nothing.

[ChipsByAl]

If the pressure sensor is not working correctly, the PCM may not "believe" it. Try disconnecting it and see if it works. Compare your current file to a 2002 Camaro file and see the differences involving a/c and the fans. You may have some codes disabled.
Al

[lowws6]

I dont think i am explaining this well. I do not have an a/c pressure sensor I am just using C1 45 and C2 14 with a resistor between them to get 4 volts at C2 14. I know it works because I can see 4 volts show up on the efi live PID. I just dont know why the PCM will not turn the fans on high. I have it set up to turn the low fan on when the intake temp is above -40 C and the a/c is on and that works fine but no high fan.

[Chevy366]

PCM must not be tripping the ground for the pins you are using for hi/low fans , what pins are you using ? 33/16, or 33/42.
Like chipsbyal said, check cal settings.

[lowws6]

I am using 33 and 42. The fans work properly other than they just dont come on high with the a/c. Here is my wiring schamatic.

http://i33.photobucket.com/albums/d60/lowws6/Gmc%20Truck/COOLINGFAN.jpg

[NU72]

I have the exact same issue. My conversion is a 0411 into a 98 truck. Fans work great when the engine coolant temperature is controlling them. But when the A/C requires the high speed fan the pin doesn't ground to trigger the relays and turn on the high speed fans. Has anyone else had this issue?? Any help or suggestions would be great. Thanks.

[ChipsByAl]

See the diagram in post #7. Do a segment swap from a 2002 Camaro into your base file. You should be using the 2002 Express Van file as your base.
Al

[NU72]

See the diagram in post #7. Do a segment swap from a 2002 Camaro into your base file. You should be using the 2002 Express Van file as your base.
Al

Ok thanks. I currently don't have anything hooked up to C1-45 and C2-14. Should I hook the pressure switch into these or install a sensor as well. Would my truck have a switch or a pressure transducer?

Which segment should I swap? I am using a 02 express van base file.

[ChipsByAl]

Swap the "System" segment. That is the part with the fan controls.
Al

[NU72]

Swap the "System" segment. That is the part with the fan controls.
Al

Ok I will. Do I need to do anything with the pressure high pressure switch?

[lowws6]

I tried the segment swap and it worked! Both fans come on high when the a/c is on but I still have one problem, the resistor I used to stand in for the a/c pressure switch is not correct and the PCM thinks the a/c pressure is too high and turns the compressor off. I don’t know what the value should be but my scan tool shows 3.3 volts. I used a 2002 camaro segment, I have a 1999 TA I will have to run the a/c on it and check what the proper value should be and find a resistor that works, when I find the proper value I will let everyone know. Sorry about not updating in a while but the truck has been in the body shop for the past 10 weeks and I just got it back.

[lowws6]

Ok I finally have it all figured out. First do the segment swap. Then install an 80K ohm resistor between Blue 45 and Red 14. This will tell the PCM that the pressure is about 160 psi. The fan comes on high with the a/c and no more overheating!

[joecar]

lowws6, thanks for posting the info :cheers: