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PCM Electronic Fan Control...

13K views 70 replies 13 participants last post by  Kamran 
#1 ·
I changed my efan over to a Volvo fan and used a thermoswitch to trigger the fan. My thermoswitch failed and I decided I wanted to see if it was possible to trigger my e-fan via the PCM. This offers two main benefits:
1 - you can have both "HIGH" and "LOW" speed (depends on your year of van)
2 - The PCM is probably the most reliable piece of equipment in the vehicle. No more depending on cheap chinesium sensors to trigger your eFan.

So about a year ago -- I worked with AstroWill and CopperFireMist to make this happen. Can't thank those guys enough -- no way this would happen without their input.

Difficulty-level: Medium
- The mechanical work involves removing the PCM connectors and adding 2 pins. If you've done it for your 4x4 swap, you'll already know how to do this.
- Obviously -- you'll need an e-fan for this too. You could use dual fans or a single two-speed fan (like me) and a way to trigger both speeds. You'll still need to use relays to control the modes -- but you can trigger those relays via the PCM. This walkthrough isn't mean to cover that -- you can see that in the numerous e-fan conversion threads.

- The tuning part involves finding someone willing to tune your van's PCM. AstroWill did this for me using a TunerCATS. Will he do it for you? I don't know. But we've done the hard work of figuring out which parameters to fiddle with -- so technically you could send your PCM out for a tune using our parameters.

Onward:
The Problem?
The problem is the V6 never came with electronic fans -- but the same 411 PCM is used for a lot of V8 equipped GM vehicles (Camaro/Corvette/etc.) that did use a two speed PCM-controlled fan (well it's actually a two-fan system, but that doesn't matter here). So technically, we guessed it was possible to "re-train" our V6 PCMs to trigger those wires just like the V8s do.

You can read the gensis of this build at the following thread:
https://www.astrosafari.com/viewtopic.p ... 0#p1350177

Here's how we did it -- CopperFireMist pulled a wiring diagram and for (01-05) you have the ability to add a two/speed and on 98-99 you can have a single speed trigger (not verified).

I'll cover the how-to for the 01-05 -- for reference, my van is a 04. I'm not sure which PCMs will play nicely with this -- but as with any tuning, there are lots of idiosyncracies, so your mileage may vary.

Step 1: Add wires to PCM connectors
You need to add a wires at:
Connector #1 (BLUE) - PIN42 for Low Speed Cooling Fan Relay Control
Connector #2 (GREEN) - PIN33 for High Speed Cooling Fan Relay Control

As you'll notice on the below wiring schematics, these pins trigger the fan on the Corvette (V8) and are empty on the Astro pinout:
pins.jpg


When these are triggered, they will send 12V negative (ground) across that circuit. So after you add the circuits, connect the other ends of these wires to the relay/relays controlling your fan circuit to use as ground triggers. I used a Volvo relay -- so I connected PIN42 to the low speed ground trigger and PIN33 to high speed ground trigger.






NOTE:
- The easiest way to get the pins is to goto your local pick-n-pull and extract a few out of an existing connector -- keep about 3 feet of wire on the end of the terminal so you can easily solder into where you want them. This will also give you practice for when you take your actual PCM connector apart. Blazers are easy to access the PCM connectors, but if you want practice with an Astro -- do it on an Astro!! Here's how to do it:

- You can also buy the connectors if you want -- Part: Delphi 12084912.

Part #2 - Tune your PCM
This is probably dependent on what Tuner you use -- but AstroWill and I used Tuner CATS, because that is what AstroWill uses. You'll want to pull a "base tune" from your van and then edit that tune -- just to make sure you don't mess something up and to have a backup if you want to go back to where you started.

There are a few intracies:
1 - You need to turn "A/C Auto Recirculation" to "Disabled" -- no idea why or what these means, but without setting this parameter the Fan triggers will PWM as opposed to ON/OFF. Hat-tip to CopperFireMist for this one.
2 - You need to set "Fan 1 Delay Time" to "2 Seconds" or the fan will trigger on shortly when you turn off your ignition regardless of temperature (no idea why -- but this fixed that behavior)...

You can see the parameters in the table below:
Parameters.jpg


I've attached a Dropbox link to the .cal file used in TunerCATS here. If you download a free trial of JET Tuner, you should be able to view this tune... but not flash your PCM with it.
https://www.dropbox.com/s/n6hvq5ho50iox ... 9.cal?dl=1
NOTE: I also changed my tire size in this tune -- so only use the fan-related stuff for this or your speedo will be off (I use 245/75/16).

Part #3 - A/C
Low-tech: I triggered my low speed fan to come on whenever the "AC Request" is active. You can get it at the back of the A/C Compressor or near the A/C switch inside the cab and can find details on what wire that is in the other e-fan threads.

High-Tech: I didn't do this -- but it seems you could get the PCM to trigger the fan based on A/C pressures, as the V8 systems do. It seems you could also get the fans to turn off at highway speeds, which would be cool too. Don't need fans for A/C when your going down the highway at 55MPH.

I outlined this to AstroWill in the following email:
I've been doing a lot of reading on the subject. The main difference is actually in the hardware, so simply installing a pressure switch and changing the AC System Type from "Analog Cycling" to "Analog" will force the compressor to run continuously while the AC Request is triggered - not great for our compressors which are meant to cycle by using the low and high pressure switches. Apparently the AC compressors in the pressure sensor style systems have some sort of variable displacement valve that allows it to run continuously and only compress the proper amount of refrigerant for a given level of pressure.

There is some genius on LS1Tech.com that figured out how to circumvent that issue though:

https://ls1tech.com/forums/conversions- ... st19705822

Essentially, by swapping some pins in the PCM, this genius puts both the high and low pressure switches in series with the A/C Request circuit, so that if either switch opens the A/C request is interrupted - causing the compressor to cycle and respecting the low side switch - just like our vans that use the "analog cycling" A/C system. However, when set to "analog", the pressure sensor will still run the fans, which is cool, because then you get PCM control of the fan for A/C. Essentially, running that 12V A/C request signal in series with both the high and low pressure switches, we can have an "analog" system and can trick the PCM into cycling the compressor, even though the "analog" system was intended to be used with an "always" running compressor.

The wiring is basically trivial - adding the pressure sensor inline probably isn't.

I can get some quotes on how much it would be to braze a fitting onto the high pressure line, but I doubt I'll be able to get around to that mod for quite a while. I'm happy to give it a shot if you're intellectually inclined. I just don't want to monopolize your tuner!

Sure would be cool - but I think PCM control of e-fans is plenty cool enough. Simply using a relay to change over the 12V+ A/C Request to ground to switch the fan is probably fine - I mean I already have a killswitch for the A/C request to the change-over relay in my current setup, so there isn't much (if any) more work necessary. I'm just happy to get rid of this crappy *** temperature sensor - and to have dual speed fans!
You'd need some brazing skill to add a couple bungs -- and if I had the skills, I probably would have tried it.

Final Words
Was this worth it? I think so. Will you? Probably not. Using a 3rd party trigger is easier - but less robust. YMMV. I enjoyed the process for learning's sake and I'd do it again if I had access to a tuner. It looks OE/Factory - which I like.

Want to make it look even more factory? Add a maxi-fuse to your existing fuse panel to power your fan like this: https://www.astrosafari.com/viewtopic.p ... 2#p1559704
 
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#6 ·
got the LS book i ordered and i like it.
here's a link to an online excerpt/article from the book about AC, Efan control, and using the AC pressure sensor. For a cable drive throttle body using the "0411" PCM they recommend the 1999-2002 camaro/firebird as the base programing :
https://www.lsenginediy.com/upgrading-g ... ing-guide/

pic of the pressure sensor as seen in the online article :
sensor.jpg


sensor for 2002 camaro as per the article, pic from listing on amazon, GM part # 13587697 :
61+4NMrLhrL._AC_SL1500_.jpg

link at amazon : https://www.amazon.com/ACDelco-15-51342 ... B01E6HCV7W

i believe the gm part # 19169412, for a 2002 camaro, is the tube that the AC pressure sensor screws into but i've seen discrepancies online for what it looks like. this is a diagram from GM parts online :
314470cc79694a9f0f5574f5c558d55f.png

i've seen both #4 and #7 on the diagram called the same thing.

i'd like to take a trip to the JY for a look-see on the real thing - a decent looking 2000 camaro has shown up :
Untitled.jpg

i'm curious to see if anything related to the camaro pressure sensor can be used on an astro, also i'd like to check out & measure the camaro e-fan setup - maybe this weekend. if/when i go i'll get some pics to post here too.

:wave:
 
#8 ·
Alot of 90s-2000 GM front wheel drive cars used that sensor too. I remember I had a 91 Sunbird with a 3.1Vv6, it used the V-5 compressor which never cycled. Also my 2002 Buick Lesabre has the same setup, with the same or same style sensor. I wonder if its in the operating system on PCM for the Astro. I have a spare PCM sitting around so I will give it a try and see if it responds.

The 91 sensor was a small-thread version of the standard 1/4 inch flare fitting. GM used it on the high-side fitting. Might be 1/8inch. Those with the older R12 vehicles will know what i mean. You had to use an adaptor to hook up to your gauge set.

Ill update when I see for sure if the PCM sees the sensor or not. Not worth changing up the A/C lines for nothing.
 
#9 ·
The switch on the accumulator of my '93 Olds Bravada (4.3L CPI, same AWD as the Astro) went bad one very, very hot summer weekend day here in MD. My husband (HVAC-R master) jumpered it to make the compressor work for our day trip to Richmond and I got a new switch after the weekend from my local parts house.

I do remember they were surprised it had an R-134a type switch already installed instead of the standard R-12 type switch, but it was definitely an R-12 system.

Installed
CyclingSwitch_1.jpg


Vehicle-side harness
CyclingSwitch_2jpg.jpg
 
#10 ·
I don't remember if this is correct -- but you may want to check if the compressors are different too. I seem to remember the duty cycle on either the LS or the V6 compressor being a bit different since the trigger devices are a bit different.

It wouldn't be that hard to braze on a new fitting to the existing AC line to get the pressure sensor where you need it -- but I don't know how to braze and to get it done professionally was a bit too expensive for my liking.

Would be pretty darn slick though!
 
#12 ·
WinnieVan said:
I don't remember if this is correct -- but you may want to check if the compressors are different too. I seem to remember the duty cycle on either the LS or the V6 compressor being a bit different since the trigger devices are a bit different.

It wouldn't be that hard to braze on a new fitting to the existing AC line to get the pressure sensor where you need it -- but I don't know how to braze and to get it done professionally was a bit too expensive for my liking.

Would be pretty darn slick though!
The Astro uses the HT6 compressor, which is designed to cycle as it isnt variable displacement. But the intent of adding this high-side pressure sensor is just for electric fan control...
 
#13 ·
sfeaver said:
Alot of 90s-2000 GM front wheel drive cars used that sensor too. I remember I had a 91 Sunbird with a 3.1Vv6, it used the V-5 compressor which never cycled. Also my 2002 Buick Lesabre has the same setup, with the same or same style sensor. I wonder if its in the operating system on PCM for the Astro. I have a spare PCM sitting around so I will give it a try and see if it responds.

The 91 sensor was a small-thread version of the standard 1/4 inch flare fitting. GM used it on the high-side fitting. Might be 1/8inch. Those with the older R12 vehicles will know what i mean. You had to use an adaptor to hook up to your gauge set.

Ill update when I see for sure if the PCM sees the sensor or not. Not worth changing up the A/C lines for nothing.
So far Based on a couple wiring diagrams I found with this sensor, the Astro tune doesn't see it. I'm not ready to give up completely though, as it may be on another input pin. I am using EfiLive to scan, and although the pid is there and says its supported, I never got it to change value.

I also havent programmed this PCM for electric fans either. So not sure if thats why its ignoring whatever input it should be, or I am using the wrong one. I dont have another EFILive license for this PCM, as its a spare. m doing this on my workbench. At some point I can try on the one in my van, but need to figure out what pin to use.

Scott
 
#14 ·
thanks sfeaver for digging with your efilive, i think the LS book i got mentioned the pin location for the sensor (in camaro/firebirds with the blue/red PCM connectors), i'll look & get back tomorrow..
i looked at the 2000 JY camaro today, it was just a v6 and is trashed - check out the difference from the pic the JY posted to today :
Untitled.jpg

the fans and relays are gone.
20201101_140809_HDR.jpg

closeup of the sensor still intact
20201101_135221_HDR.jpg

the computer is not an "0411"
20201101_140645_Burst02.jpg

20201101_140739.jpg

20201101_140735_Burst01.jpg

i went ahead and snipped out the tubing bung & wiring just to familiarize myself with the parts (the PCM connectors are blue/white), i'll add a pic tomorrow.

this pic is totally unrelated but totally badass :
arton81629.jpg

:rockon:
 
#18 ·
sfeaver said:
It does see it! Using pin C2-14 as the input, with C1-45 at 5v and C2-57 as ground. I thought thats what I used last night, but must not have been.

So it looks like it will work after all!

What threads were on that sensor?

Scott
wonderful !!!
i left the piece at work to clean it & take pictures - will take the sensor off the tubing tomorrow & see if i can identify the threads.....
 
#21 ·
stent said:
looking online, found this for sensor thread size :

got the OEM part number from amazon, confirmed it on GMPartsDirect.com as fitting 2000 camaro.
:wave:
GM 13587697 ACDelco 15-51342 https://amzn.to/3l71OW8
Would be awesome if it works for $30
 
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