1971 Stepside LS Build

[derotoreut]

I would like to know the same ^^^^^. Did you use the trinary or binary? Also, I'm assuming your tuner had to somehow set this up in his tune with their PCM and harness? Great idea and excellent work. Keep it up.

[1971Stepside]

'm glad you went with the transducer. I will be curious so see how this all turns out as I may end up using that module as well. So did you end up using the VA binary switch for the compressor as well? In your last picture I see something installed but can't tell from binary to trinary.

With the transducer installed you only use the binary switch. I have a brand new trinary that I won't be using now.

[TA_C10]

If I understand this correctly, I've just finished my setup, the transducer is a GM factory device that has been used for quite some time in the LS platform. Im surprised in all the big threads in the LS forums there isn't more talk about it. Basically the PCM uses this device to control idle with A/C, control fans with A/C(high pressure), and then the binary is used only for the A/C compressor as a high pressure switch to turn off the compressor.

The fact that it's OEM for our PCM is common sense to me that this is the method we should be discussing to integrate the big 3(A/C, fans, idle). Your tuner can configure all of this if it's disabled in your particular model PCM. I'm not sure how many models PCM it works with but I'm sure someone in this forum knows.

I did all kinds of research on this and all I found was people doing the trinary half azz redneck engineering trying to make this work and not throw codes in PCM. When the whole time GM makes this transducer that does it all. And I'm joking about the redneck stuff, trinary works fine, but you don't get idle fix and it's really not the best way to do this IMO.

I found out about it just before I finished my trinary setup and was pissed.... .

That's how it goes though, now I'm planning to find out if it works with my gen III PCM and I will switch to the transducer and binary, and remove all that custom wiring for trinary.

Ok, rant over...

Transducer:
https://www.bp-automotive.com/produc...re-transducer/

Hey Stepside, did you see this from BP??
https://www.bp-automotive.com/produc...re-transducer/

.

[TA_C10]

Based on this part, it appears GM has had this out back in LS1 technology....

https://www.jiksawonline.com/index.p...ucts_id=123387

[MDPotter]

Okay, I'll bite. How exactly does the transducer function in terms of fan trigger?TA and I developed a diagram to work with the trinary switch so that when the line pressure reached its high setpoint, it would trigger both fans to run full speed. It's essentially setup to where Vintage Air stands alone from the PCM in terms of controlling the fans.

A few questions:
-Does this transducer provide a ground or some sort of signal when the AC is on?
-Or just when the line pressure reaches its high setpoint?
-Does this transducer signal get sent to the PCM instead of the fuse block that controls the fans? If it goes to the PCM, I'm assuming it takes over control of the fans?

I'd like to see a wiring diagram/controls sequence of this. I'll have to do some research. Where is ls1nova71?

[TA_C10]

Originally Posted by MDPotter

Okay, I'll bite. How exactly does the transducer function in terms of fan trigger?TA and I developed a diagram to work with the trinary switch so that when the line pressure reached its high setpoint, it would trigger both fans to run full speed. It's essentially setup to where Vintage Air stands alone from the PCM in terms of controlling the fans.

A few questions:
-Does this transducer provide a ground or some sort of signal when the AC is on?
-Or just when the line pressure reaches its high setpoint?
-Does this transducer signal get sent to the PCM instead of the fuse block that controls the fans? If it goes to the PCM, I'm assuming it takes over control of the fans?

I'd like to see a wiring diagram/controls sequence of this. I'll have to do some research.

From my understanding(could be wrong here) the transducer is pressure based. So it constantly monitors the A/C pressure and based on that(signaling to PCM) it controls the idle and fans. Then the binary switch is strictly used for the compressor shut-off at high pressure threshold.

It works in conjunction with the PCM's other fan controls. Basically allowing the PCM to control fans based on coolant temp AND A/C pressure.

Yeah man, it's nerve racking I never found this during all the research we were doing on this. Months of researching, and several days worth of wiring truck and building diagrams...

.

[sprint_9]

The transducer is a sensor that sends voltage back to the ecm that corresponds with pressure in the ac system. The ecm converts this voltage to a pressure reading. You can setup the fans related to a pressure table within the ecm when tuning.

At least this is what I've looked at on my Gen 4.

I commented in a thread in the ls swap forum with some pictures of mine and some info on it.

[1971Stepside]

From my understanding(could be wrong here) the transducer is pressure based. So it constantly monitors the A/C pressure and based on that(signaling to PCM) it controls the idle and fans. Then the binary switch is strictly used for the compressor shut-off at high pressure threshold.

It works in conjunction with the PCM's other fan controls. Basically allowing the PCM to control fans based on coolant temp AND A/C pressure.

Yeah man, it's nerve racking I never found this during all the research we were doing on this. Months of researching, and several days worth of wiring truck and building diagrams.

This is correct. I know BP Automotive has some information on this in their FAQ section under AC. I called and discussed this with VA and they said just use the Trinary switch, but it didn't control idle. I called BP Automotive because my harness had the fitting for the GM transducer. Once they explained it to me it seemed like a much better way to run the AC. The #8 fitting with the transducer was like $70.

[MDPotter]

sprint, I found the thread you commented in. http://67-72chevytrucks.com/vboard/s...d.php?t=776599

So basically, using this transducer eliminates the need for the diodes and resistors and tapping into the low and high speed trigger wires at your fan fuse block and instead uses the readings from the pressure line to provide feedback to the PCM which in turns does whatever you tell it to do, via those low and high speed trigger wires. Right?

[TA_C10]

Originally Posted by MDPotter

sprint, I found the thread you commented in. http://67-72chevytrucks.com/vboard/s...d.php?t=776599

So basically, using this transducer eliminates the need for the diodes and resistors and tapping into the low and high speed trigger wires at your fan fuse block and instead uses the readings from the pressure line to provide feedback to the PCM which in turns does whatever you tell it to do, via those low and high speed trigger wires. Right?

This was the reason for my rant. Yes. All that work we did man. Out the window. And not only that but all that work still didn't get us idle control!!

This is the way to go, OEM, built-in functionality.

.

[sprint_9]

Yea that was the thread, reading through it again First c10 said his didnt work so who knows if it actually works. I havent yet gotten that far with mine and everything Ive done thus far has been from some reading.

Of coarse the Gen 3 vs. Gen 4 differences most likely come into play. I assume its easier to get working with a Gen 3 since Gen 4 had started to transition to CAN Bus and more of this on the BCM.

So your Trinary switch diagram might not go to waste. If mine doesnt work Im moving over to it and forgetting about trying to add on a CAN Bus box or some other nonsense.

[MDPotter]

For me, I don't care about idle control since it's worked just fine on my dad's truck. I just want fan control. It would be cool to have the PCM control the fans as it relates to AC, but it seems like a lot of work compared to the diagram we came up with. The only wrinkle with the diodes/resistors route is putting switched power to the fans so that in case the trinary goes bad in the closed position it doesn't run down the battery.

It's not wasted effort! I think we'll probably run with that setup at this point.

[derotoreut]

So how complicated would this be to adapt this transducer control to my swap. I haven't completed my wiring yet. I'm assuming if I wanted to go the transducer route it's not as simple as installing the transducer and pinning somehow to the PCM. I would believe there would have to be some reprogramming of the PCM correct?

[cornerstone]

Originally Posted by derotoreut

So how complicated would this be to adapt this transducer control to my swap. I haven't completed my wiring yet. I'm assuming if I wanted to go the transducer route it's not as simple as installing the transducer and pinning somehow to the PCM. I would believe there would have to be some reprogramming of the PCM correct?

I'm listening too. It'll be coming down the for me also. What and how to do it the best way from the get go.

[TA_C10]

I've found that these transducers started around 96ish. So they've been around a while. If I understand it correctly...... you either get the weld-in bung if you have that ability or you get the crimp-on style adapter and install inline. The transducer is then installed. If you don't have a harness with this plug you will need to install the necessary wires (see post above) and pin them in the PCM. No big deal. Buy the plug, and wire it right(same post above). Done. Your fans are already wired with 3 relay setup. Then you tune the PCM how you want, either stock or custom. Everyone usually needs to get their PCM tuned anyway so depending on your mods all this gets done at same time.

I think it's easier because you don't have to research all the trinary stuff and wire it up. Of course we've pulled together with help of many folks all that work for ya now so others won't know that time spent I guess. But your also not messing with both diodes and resistors. And you don't have the problem if trinary goes bad and using switched power as it's PCM controlled.

I dunno. Maybe I just think different on this one. I'm biased on this particular subject however...

[derotoreut]

TA_C10: I have been following your build and read through what you were planning with the 3-relays, diodes and resistors. You really put a great deal of work into it, and I applaud your efforts. Honestly it sounded good, but I was not planning to go that way because when Tilden built my harness and programmed my PCM, they used only the 2-relay method for fan control. They already wired in two relays and installed them in a weatherproof box as part of my harness. My plan (which may still happen) was to tap into the trigger from one of the fans, and tie that into the trinary switch. This was the recommendation by my harness builder (Tilden). However, if it is easier and more effective to go the transducer route, I will consider it. In order for me to do it, I think I would buy the drier already set up with the transducer and binary switch since there is no good location for me to install the transducer. Plus I'm using Vintage Air's EZ-Clip system for hose installation. My harness has already been programmed by Tilden, so that would mean I'd have to have it redone? Great info going on here. Sorry Stepside if we've hijacked your build thread for this.

[TA_C10]

Originally Posted by derotoreut

My harness has already been programmed by Tilden, so that would mean I'd have to have it redone? Great info going on here. Sorry Stepside if we've hijacked your build thread for this.

Derotoreut, I would first contact your tuner and make sure your PCM is good for the transducer. Then as long as your good with opening your harness up to install those wires and pin them(unless you have that transducer plug available in your harness already) then yes you have to add this to your harness, and you should be good to go.

Now I say this because that's what I would do. But I don't know for sure, I have only spent a short time researching this. I'm not a GM mechanic. I am however a systems engineer for an airline, I build automation for server systems and networks so I understand most of the functions of the GM PCM and in my opinion, anything that can be controlled by the LS computer is going to be better than standalone because you're going to have integration with these components and that's going to give you more options, fewer external weak points, and a better running engine overall.

The only reason the transducer wouldn't work is if your model of PCM either doesn't have that feature built in, or the generation you have uses a different set of parameters specific to a particular transducer module meaning it would be specific to year. Your tuner can tell you these answers.

But again, I'm no expert on this. And stepside, I apologise as well for all these posts in your thread. If you don't want them here we can get a moderator to cut these posts from your thread and stick them in a new post over in LS forum.

.

[Custom 68]

Lots of great information.
I do need to see this. So much detail. I got mine out today but looks like more rain next week
Dave

[1971Stepside]

Wow! What a discussion I didn't think the transducer was something unique for the swaps. Hope it helps others.

We had a great weather day yesterday, so I went to pick and pull (therapy) and wandered around. I found an 06 two door Civic with really clean weatherstrips so I pulled them. $14 later I went home and they do fit our doors perfectly. The doors close easily with a good seal around the whole door. I just don't like they way they look. The extra lip that goes around the interior trim on the car looks really out of place on our trucks. I don't think you could ever trim it and make it look right. I wonder if the Dakota weatherstrip has this as well? I've also heard that semi truck weatherstripping fits. It was worth $14 to see if I liked them I guess.

[1971Stepside]

I'm going to need more parts for this pandemic that we have on, but I did pick up some nice 72 door panels this weekend. They will be recovered, but a solid base to work from.

[MDPotter]

At this point I would not mind being "forced" to "work" from home!

[1971Stepside]

Found another old pic of the truck from High School days. I love the Playboy Bunny air freshener and my amazing mullet. Circa 1986

[MDPotter]

Do you still have the air freshener and the mullet?

[TA_C10]

The truck looks good in 86, the mullet, not so much lol. Texas Chainsaw Massacre ??

The sliding glass window, did you put that in back then?

[1971Stepside]

Do you still have the air freshener and the mullet?

I don't have either, but the potential is still there thankfully.

The truck looks good in 86, the mullet, not so much lol. Texas Chainsaw Massacre ??

The sliding glass window, did you put that in back then?

I put the sliding glass in it back in the day. That was part of the AC system I had installed.