Electric Fan Conversion AC Issue

[wstefan21]

Why did you spend so much? You didn't need to upgrade the OS you could have found a similar OS and just did a segment swap between OS. That's what I do so I only spent two credits when I license my PCM and OS then I found other two files with the same OS and swapped over the segments I needed. Here's an example of what I did I used my original OS which was a 4.3 with 4l60e I did a engine segment swap with an 04 Tahoe with a 5.3 then I did a segment swap from a 2004 SSR for the 4l60e and it didn't cost me any extra credits.

The p01 more likely don't have the drivers inside for the AC high pressure switch switch try to find a 411 PCM out of 02 with blue and red connector. I would say go to a P59 then you would have to rewire your red connector because the green connector is pined slightly different from Red connector.

Yeah... I know that now, but I tried the segment swap and had people tell me the OS was the problem.

I agree, there's got to be something missing from the hardware or drivers.

I'd love to switch to a newer pcm, but unfortunately the pcm is under the dash on this application and in order to re-wire everything I'd have to pull the dash to change the pinouts drastically and I'm really not wanting to go down that rabbit hole if I can help it! I'm going to try to find a 0411 next week and swap that to see if that makes a difference.

[Life is an Enigma]

Yeah... I know that now, but I tried the segment swap and had people tell me the OS was the problem.

I agree, there's got to be something missing from the hardware or drivers.

I'd love to switch to a newer pcm, but unfortunately the pcm is under the dash on this application and in order to re-wire everything I'd have to pull the dash to change the pinouts drastically and I'm really not wanting to go down that rabbit hole if I can help it! I'm going to try to find a 0411 next week and swap that to see if that makes a difference.

The 2002 Chevy Astro van using 411 PCM. And they're usually plenty of Astro in the wrecking yard.

[Keep]

A trinary switch on the high side is the easy way to run fan 2 without a pressure sensor. It is what I used for electric fans with a black box that had a single fan output. When you are rolling down the road the condenser has enough air flow that the fan turns off.

I just want to highlight this post. I am running an 6L LS in a 57 chevy with a 1999 pcm (p01 I believe). Installed a vintage air trinary switch, wired into the high speed relay on the fan. Works like a charm and no fighting with tunes. Only thing it does not do is bump the idle when the AC is on. But with the cam, it already idles at 850 so not really needed.

[wstefan21]

I just want to highlight this post. I am running an 6L LS in a 57 chevy with a 1999 pcm (p01 I believe). Installed a vintage air trinary switch, wired into the high speed relay on the fan. Works like a charm and no fighting with tunes. Only thing it does not do is bump the idle when the AC is on. But with the cam, it already idles at 850 so not really needed.

I completely agree that this is a fantastic option. I've always been the one to over engineer everything. I like the feature where the fans turn off above a certain speed, and the extra safety/data you get with the pressure sensor. I also really like the idea that I can change the settings at will and aren't physically set. Of course, that said, the trinary switch works just fine and is a great option, but for me, the extra features and the fact I'm a bit masochistic about decisions regarding fixing my cars (and the fact I just spent $60 wiring the pressure switch) sets my fateful decision. I am admittedly the king of the sunk cost fallacy.

[wstefan21]

The 2002 Chevy Astro van using 411 PCM. And they're usually plenty of Astro in the wrecking yard.

Sure are! The junkyard closest to me is pretty small unfortunately so we'll see what I can find. Sure beats driving an hour each way to get to the bigger ones. I could always order one and spare the pain of going to the yard, but I really enjoy going to walk around sometimes.

[Fast4.7]

I just want to highlight this post. I am running an 6L LS in a 57 chevy with a 1999 pcm (p01 I believe). Installed a vintage air trinary switch, wired into the high speed relay on the fan. Works like a charm and no fighting with tunes. Only thing it does not do is bump the idle when the AC is on. But with the cam, it already idles at 850 so not really needed.

My low fan was triggered by the one output on the black box PCM. Its an auxiliary fan control. My high fan was controlled by the trinary switch as well as a 195F thermostatic switch in the passenger side head. Low fan would come on courtesy of the PCM. If the PCM failed to energize the fan like when my CTS started randomly reading -40F in the middle of summer the fan switch and ac pressure switch still activated one fan on high speed. System was double redundant.

[Life is an Enigma]

On my setup I copied GM relay setup the parallel/series with the high and low fan control out of the PCM. It works really well for me. The real trick is finding the right temperature settings for the area that you're in. Especially here in California where the humidity gets down into the low teens. That dry heat is hard on engines.

Ls-Fan Relay.jpg

[Keep]

I completely agree that this is a fantastic option. I've always been the one to over engineer everything. I like the feature where the fans turn off above a certain speed, and the extra safety/data you get with the pressure sensor. I also really like the idea that I can change the settings at will and aren't physically set. Of course, that said, the trinary switch works just fine and is a great option, but for me, the extra features and the fact I'm a bit masochistic about decisions regarding fixing my cars (and the fact I just spent $60 wiring the pressure switch) sets my fateful decision. I am admittedly the king of the sunk cost fallacy.

lol understand completely!

The fan will shut itself off once you reach a speed where there is enough airflow through the condenser to keep the pressures down, i do not know what exactly that speed is, but it does shut off. The only time I really notice the fan being on is when I am driving in the city. Once you hit the open road, there is enough airflow to keep the pressures down.

[Keep]

My low fan was triggered by the one output on the black box PCM. Its an auxiliary fan control. My high fan was controlled by the trinary switch as well as a 195F thermostatic switch in the passenger side head. Low fan would come on courtesy of the PCM. If the PCM failed to energize the fan like when my CTS started randomly reading -40F in the middle of summer the fan switch and ac pressure switch still activated one fan on high speed. System was double redundant.

My PCM controls them both, low and high, but the trinary trips the high (shuts off the low) when I turn on the AC and the pressure builds.

[Fast4.7]

My PCM controls them both, low and high, but the trinary trips the high (shuts off the low) when I turn on the AC and the pressure builds.

That is the way mine was when it had the black box. With the 0411 and later with the P59 both were PCM controlled. I have since ditched the electrics and gone with a Duramax fan on a TBSS thermal fan clutch. I recently added a Flexalite 16" 3,000 cfm puller between the radiator and mechanical fan. I have an electronic TBSS fan clutch on the way though. Low fan will trigger the 16" electric. High fan will trigger a relay to kick in the electronic clutch at full speed. I am not going to use the optical speed sensor or PWM control the clutch. Its going to be on or off as needed. Should save some HP and Fuel compared to the old thermal clutch when the mechanical is not needed. With the electric puller coming on with the ac anyway it takes a few minutes of idling, a few miles of in-town driving or some long uphill climbs to fully bring in the clutch fan. I like the idea of PCM controlling the clutch fan so that I can adjust the point where it works. There are times it would be nice if the fan engaged sooner and yet others where it stays engaged far too long. For example when it is parked in the sun and it is 108F outside. It would be nice if the clutch fan activated immediately with the ac headpressure to help kick start the ac cooling.

[wstefan21]

Sorry for the delayed response. Finally got the new 0411 PCM and had time to mess with it.

My assumptions were correct. The 0411 can read the pressure sensor where the old one would not. This one also will stop responding to analog 12V ac signal when a/c type is set to serial. Analog also does NOT react to the low-pressure cycling switch at all.

The most notable thing, I did not notice it turning off even when the pressure went below 20psi (yes, I was low on refrigerant), so if you do not have a newer variable displacement compressor (mine is an old r4), you need to wire your old cycling switch inline your 12V enable signal with the high-pressure sensor.

Blows nice and cool now! Very happy with the results. And yes. I acknowledge that there were cheaper options of going about this, and this was probably just my OCD, but for those who want control of fan timing vs pressure, this is a great option! Hope this helps someone.

[Fast4.7]

Sorry for the delayed response. Finally got the new 0411 PCM and had time to mess with it.

My assumptions were correct. The 0411 can read the pressure sensor where the old one would not. This one also will stop responding to analog 12V ac signal when a/c type is set to serial. Analog also does NOT react to the low-pressure cycling switch at all.

The most notable thing, I did not notice it turning off even when the pressure went below 20psi (yes, I was low on refrigerant), so if you do not have a newer variable displacement compressor (mine is an old r4), you need to wire your old cycling switch inline your 12V enable signal with the high-pressure sensor.

Blows nice and cool now! Very happy with the results. And yes. I acknowledge that there were cheaper options of going about this, and this was probably just my OCD, but for those who want control of fan timing vs pressure, this is a great option! Hope this helps someone.

I understand the OCD control issue. I put the electric clutch on and wired it up to Fan2 via a relay. Its nice to have PCM control over the clutch fans operation. I have found in the morning and evening when it is cooler outside, the clutch seldom fully engages outside of the first 15-30 seconds it takes for the fluid to redistribute on a cold start. In the heat of the day it runs a bit until the interior cools down. Once the interior cools down and the ac blower speeds are reduced the clutch fan seldom engages.

[Aggie3rdGen]

Hello all,
I'm having similar A/C control issues with my P01 ECM and trinary switch. Vehicle is 86 Camaro and old binary pressure cycling switch is removed. Compressor will engage if A/C is commanded by HVAC head unit (wired through ECM), regardless of the pressure in the system. Does the P01/trinary switch have the ability/logic to control A/C clutch or is the old binary cycling switch absolutely necessary for compressor protection?

[Life is an Enigma]

Hello all,
I'm having similar A/C control issues with my P01 ECM and trinary switch. Vehicle is 86 Camaro and old binary pressure cycling switch is removed. Compressor will engage if A/C is commanded by HVAC head unit (wired through ECM), regardless of the pressure in the system. Does the P01/trinary switch have the ability/logic to control A/C clutch or is the old binary cycling switch absolutely necessary for compressor protection?

Yes the low pressure cycling switch is necessary. It stops the A/C System from freezing up when the pressure is get too low about 20 psi.

[dlb21964]

Theres so many different responses out on the interwebz about this AC stuff and LS Swaps.
Hopefully my setup works properly. I’m using a trinary switch, along with 3 relays and a ground wire going to the PCM per Vintage Air tech.

AC on brings low speed fans on, and if pressure gets to a certain level because of temp, fans will then run on high.

Not sure if fans shut off above 40mph or not. I?m guessing they don’t.

[[email protected]]

Sorry for the delayed response. Finally got the new 0411 PCM and had time to mess with it.

My assumptions were correct. The 0411 can read the pressure sensor where the old one would not. This one also will stop responding to analog 12V ac signal when a/c type is set to serial. Analog also does NOT react to the low-pressure cycling switch at all.

The most notable thing, I did not notice it turning off even when the pressure went below 20psi (yes, I was low on refrigerant), so if you do not have a newer variable displacement compressor (mine is an old r4), you need to wire your old cycling switch inline your 12V enable signal with the high-pressure sensor.

Blows nice and cool now! Very happy with the results. And yes. I acknowledge that there were cheaper options of going about this, and this was probably just my OCD, but for those who want control of fan timing vs pressure, this is a great option! Hope this helps someone.

Hello wstefan21,

I am following up on your final configuration. I have been searching for a solution to my issue and I think you may have solved it. I have a 2001 GMC Sierra with a fixed AC compressor with low pressure switch for cycling. I just did the BP harness add for the 2003+ 3 wire pressure sensor and converted to efans from a newer truck. I noticed the lowside ac lines frosting over after the install. I do not think my compressor is cycling and is staying on as long as the ac is on. The fans are working off the pressure switch and temp settings. Are you saying you were able to use the Efans tables in the P01 ECM to control fans like a 2003+ truck and wire the low pressure sensor between the PCM and compressor clutch to return the cycle feature back to the legacy fixed compressor?

Any help is appreciated!!!

[chrisxiv]

Hello wstefan21,

I am following up on your final configuration. I have been searching for a solution to my issue and I think you may have solved it. I have a 2001 GMC Sierra with a fixed AC compressor with low pressure switch for cycling. I just did the BP harness add for the 2003+ 3 wire pressure sensor and converted to efans from a newer truck. I noticed the lowside ac lines frosting over after the install. I do not think my compressor is cycling and is staying on as long as the ac is on. The fans are working off the pressure switch and temp settings. Are you saying you were able to use the Efans tables in the P01 ECM to control fans like a 2003+ truck and wire the low pressure sensor between the PCM and compressor clutch to return the cycle feature back to the legacy fixed compressor?

Any help is appreciated!!!

I was under the impression that you needed to change the OS in order for the PCM to control the 3 wire AC pressure switch... I also thought that the pre-2002 trucks(maybe off one year) had a different type of AC system on them.