Ls swapped, ac questions

[95bastard]

1995 ls (4.8) swapped, has efans. Everything on truck works as it should, only issue is getting efans to work with ac. I am using HP tuners, have pin 17 hooked to ac wiring, pin 55 grounded (totally stock 95 ac system). Still having issues, can’t get efans to kick on with ac, have system set to analog, adjusted speeds to kick on and off...I’m lost, thanks for any input.

 

[kewljay223]

what year is the motor? from your pin numbers you mentioned, im assuming its the older 99-02 pcm. you say you have those pins hooked up but didnt explain to what..... but those pins are INPUTS to the pcm in which it then tells the fans to turn on or off. not sure how you have the fan system actually wired up, but the pcm uses pins 42(blue) and 33(red) to ground your high/low speed relays. Those pins are what activate the fans to kick on and off at whatever temps are set in the tune. So if you have those hooked to your relays, that explains why its not working.

Just as a note, your pin 17 (ac request signal) is a digital signal sent from the BCM to the PCM. If you dont have the BCM, this is useless and you will need to add another relay to kick fans on for AC. Below is a diagram for a dual fan setup with high/low and AC without the bcm. This image is all over google but I edited it by adding a 4th relay to it (AND A DIODE) to make everything work. This should help you out considerably. Disregard wire colors as they pertain to my truck.

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also google LT1swap.com for pinouts and good swap info.

 

[RDF1]

Also can you post your tune?


Sent from my HiDiNg PlAcE

 

[Jglew82]

95, what I did was use my obs AC system as a standalone and did not wire to the '04 PCM, but I wired a relay in to ground the E-fan relay when I engage the AC clutch. This way, the PCM will provide a ground as usual to power the fans when it reaches set temp, but the "AC grounding relay" will kick them on whenever the AC is on regardless of temp. Here is how I have my relay and fuse block wired.

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[95bastard]

Thanks for the replies. My donor motor/pcm are from an 01 Silverado. I have pin 17 hooked to the wire that powers up my ac compressor, pin 55 is hooked to ground. I am wanting to run the fans via the pcm, my research says that if I do that the fans will kick on below speeds of say 30 mph, and off at speeds above 35 mph. The idea being, I don’t need the efans to run at speeds above 35 mph. I have no problem wiring in a relay to engage the fans whenever the ac is active, but running them at highway speed is not needed.

 

[RDF1]

There is a setting in the fans for the AC to trigger fans if ECT is above a certain number. I'd have to look it up

Sent from my HiDiNg PlAcE

 

[Ken K]

With all being said, what temps would someone suggest the fan #1 and fan #2 come on with coolant temperature? Curious to know before getting my PCM programmed.
As for controlling A/C fans for vehicle speed, would seem to make sense, but I don't think I have ever come across a GM car or truck that operates by speed as system pressures are normally inputs for A/C fan control. Allowing the condenser to reach a higher temp will aid in heat transfer to remove latent heat. Typically done with high side pressure setting input from switch on A/C line. They used "Binary" or Trinary" switches to achieve proper HVAC fan control. The PCM overrides fan control relays to control engine coolant temps.

 

[Jglew82]

With all being said, what temps would someone suggest the fan #1 and fan #2 come on with coolant temperature? Curious to know before getting my PCM programmed.
As for controlling A/C fans for vehicle speed, would seem to make sense, but I don't think I have ever come across a GM car or truck that operates by speed as system pressures are normally inputs for A/C fan control. Allowing the condenser to reach a higher temp will aid in heat transfer to remove latent heat. Typically done with high side pressure setting input from switch on A/C line. They used "Binary" or Trinary" switches to achieve proper HVAC fan control. The PCM overrides fan control relays to control engine coolant temps.

My Low and High come on at 201 and 204 respectively, kick off 3 degrees below those set points.

I think they were talking about the fans disabling above a certain speed, as the air moving over the condenser is sufficient at those speeds, so they disable to take the load off the alt.

 

[Ken K]

Electrical load shedding is a big deal in newer vehicles and I am familiar with 3 different strategies GM uses and the electronics used. With a normal 195 degree F thermostat, the temps you listed make sense. Just have not seen anyone post what works on their truck that had an "LS" swap.
Thanks.

 

[Jglew82]

Just have not seen anyone post what works on their truck that had an "LS" swap.
Thanks.

Well, that's why I responded since that is exactly what is working flawlessly in my LS swap.