A/C install, how to set the FAN G20 chevy Van LS swap

[torque_383]

Hello,
I?m new to this forum. I?m from Belgium and LS swapped a 1981 G20 chevy van.
ECU: 2001 GMC Yukon 1500 5.3 GM_P01
I installed a Sanden SD5H09 A/C compressor and wired it like this:

aangepast schema.jpg

So you have 12V through the ac low pressure switch ( as soon I set the lever on the dash on A/C ) feeding de relay ( red circle ) and this signal goes also to pin 17 of the ecu ( ac request signal ).
Pin 43 ( yellow circle ) is also connected to the relay.
Because my 1981 Van doesn?t had a pressure sensor, I installed a 20915 sensor on the A/C system and wired it to the ECU ( pin 45, 57 and 14 ).
The ac is working WHEN I disconnect the wire from pin 43 ( yellow circle ) and put ground to pin 86 from the relays. The AC is controlled by the AC low pressure sensor.
Now, what I want to do is
1. that the ECU can control the AC. This will happens by connecting the pin 43 to pin 68 from the relay. The ECU has to disable the AC when the engine RPM Is going above 5000 rpm.
2. The ECU controls the fan. So when the AC is on, the electric fans will also go on.
Can anyone tell me if my schematic is the way to go? And where in hp tuners I can set the fan?s to go on when the ac is on. And where the ecu can control the ac.
My tuner and I have tried a bunch of settings but we cannot find how to set the fan on and controlling the ac.
Any help is welcome, thanks!!!

[johnny6.0]

I guess you already know this excellent source of information.
https://www.lt1swap.com/airconditioning.htm

I did a swap with a 2004 LQ4 (P59, grenn/blue conn) in my 1986 K20 and did it the same way and it works flawlessly. The only thing I had to do was to solder two resistors and a capacitor on the PCM, because it lacks 12V AC Request on C2-17. A common problem with drive by wire pcms.
Now the ac request is controlled via the ac module switch (dark green wire) inline with the orignal low pressure switch on the accumulator and for saftey reason a high cut out switch to pin C2-17. I'm using the R4 compressor, clutch is switched via relais, relais is connected to +12v and C2-43 on the pcm.
I than fabricated an adapter which screws on the SAE port of the high pressure side and adapted the M12x1,5 thread from the transducer to the line. For my understanding the pressure transducer only read the pressure and adjust engine load recordingly to A/C pressure in the system.
I converted to a dual fan setup for the engine cooler/A/C-condenser. Everything works perfect. First fan switches on when A/C is turned on a compressor clutch is engaged.

The question is, why using the pressure transducer and not keeping it simple and using low pressure switch and for safety reasons a high cut out switch without a transducer?

20230801_211940.jpg20230801_211846.jpg20230801_211913.jpg

Bildschirmfoto vom 2023-12-03 22-04-29.pngBildschirmfoto vom 2023-12-03 22-05-32.png

[torque_383]

Thanks for your reply.
Indeed, I used the information on the link you send me.
I have a bleu red pcm, so no drive by wire. I have de same low pressure switch as in your second pic.
I used that 12V signal to pin 17. And I get a “ac request” when I use my OBD scanner. So the signal is coming in to the PCM. On the high pressure side I used the 3 pin pressure sensor 20915.
https://www.amazon.com/Four-Seasons-.../dp/B000E0QR2G
The idea of using the 3 pin pressure sensor was to control the fans by the ECU, so when the pressure is high, the fan kick in.
But that doesn’t work or we are doing something wrong in hp tuners. Thanks for the hp tuners screen shots. I will pass them to my tuner.
Is there a logging ability in hp tuners to read the pressure from the 3 pin high pressure switch?
Thanks!!

[johnny6.0]

But that doesn?t work or we are doing something wrong in hp tuners. Thanks for the hp tuners screen shots. I will pass them to my tuner.
Is there a logging ability in hp tuners to read the pressure from the 3 pin high pressure switch?
Thanks!!

Hope this helps a bit further. I had to set the pressure values accordingly. Took that from a 2005/2006 Silverado.

Don't know if there is a logging point for the A/C pressure. But when you should find them in the VCM Scanner.

By the way, this is how I wired my fans.
http://67-72chevytrucks.com/vboard/s...30&postcount=9

[torque_383]

thanks for you reply. My tuner has also set the pressure value's. We tried to set them higher and lower, but nothings happens with the fan.
the scanner he use cannot ( or we didn't find it ) read the pressure value of the ac pressure sensor, I hoped it was available in hp tuners?
thanks for you schematic. I see you use the green/bleu PCM. I think it is different of the bleu/red, because i cannot set half speed on my fan, only on of off.
i think there is also a difference in programming hp tuners for ac for the green/bleu of bleu/red pcm?

[johnny6.0]

Maybe your OS doesn't support the A/C pressure transducer. I'm not an expert but this could explain why there's no information about it.
The only thing I found is AC Pressure Sensor (Voltage).

Bildschirmfoto vom 2023-12-05 13-47-54.png

Are the fans itself working depending on the ECT?

[torque_383]

hello, thanks for your reply. what do you mean with OS? os from the laptop where hp tuners is on installed?
the fans are working normal, there are 2 fans and they are controlled by the ECU. So when the engine gets to hot, the first fan turns on. And if the temp keeps rising, the second fan turns on.

[johnny6.0]

The OS from your PCM. https://github.com/BoredTruckOwner/L...ine_Repository

But as stated on the lt1swap.com you can program either pcm type with transducer option.

Did you download another OS from the HPT repository and looked inside what setting are valid for other cars/trucks from the same year? Especially for 2001 F-Body which used the transducer with P01 if I'm not wrong at this point.

Stupid question, but your A/C is working fine? Clutch turns on, pressure is build up in the system?

[Brendang2000]

QUOTE:
hello, thanks for looking in to it. Wierd the link doesn't work:
https://forum.hptuners.com/showthrea...vy-Van-LS-swap
this is the tread:
Thread: A/C install, how to set the FAN G20 chevy Van LS swap
I think my hardware setup is good. I'm looking for the settings in HP tuners. maybee some screenshots from the settings you did to get the A/C, fans working?
thanks!


I figured I'd reply on your thread. I'm also using a Blue/Green ECU, but an express van version, so I'm guessing the programming will be different than yours. I tried using a Blu/Green from a Silverado and could not get the A/C to work, then all I did was swap to the van ecu and it worked; was told not all hardware is installed in all ECUs. Pictures are how I have the van ECU programmed.


AC.pngfans.png

[johnny6.0]

QUOTE:
I tried using a Blu/Green from a Silverado and could not get the A/C to work, then all I did was swap to the van ecu and it worked; was told not all hardware is installed in all ECUs.

For your 05 Silverado problem look here: https://forum.hptuners.com/showthrea...l=1#post753418
No need for another PCM if you know someone who has good knowledge about smd soldering.

[torque_383]

The OS from your PCM. https://github.com/BoredTruckOwner/L...ine_Repository

But as stated on the lt1swap.com you can program either pcm type with transducer option.

Did you download another OS from the HPT repository and looked inside what setting are valid for other cars/trucks from the same year? Especially for 2001 F-Body which used the transducer with P01 if I'm not wrong at this point.

Stupid question, but your A/C is working fine? Clutch turns on, pressure is build up in the system?

Thanks for you reply.

I will pass it to my tuner regarding the OS. It was a Yukon PCM that had ac on the car.

My A/C works, it' all brand new. turns on and of with the low pressure sensor. It basicly works without the PCM, but I now have to put the electric fans on manualy. And I want to controll the fans ( and A/C ) by the PCM.

[Fast4.7]

I have never had much luck keeping the GM vans cool using electric fans. My 87 G20 had far better cooling using the clutch fan and OE shroud. I had my 6.0L in the van using mounts that put the 6.0 in stock location relative to the bellhousing and transmission. I first tried LS1 electric fans and could not keep it cool. I then put a fan clutch for a 2006 Ram 4.7L that has a longer barrel nut and a 2006 Ford F150 3V 5.4L fan. Fan fit the OE ahroud perfectly and the longer fan clutch positioned the fan perfectly in the shroud. Even beating on it with the ac on it always ran cool even on a 110F day. I pulled the 6.0L out of it because it was gutless in normal driving and put a mildly cammed L31 350 back into it.