Using PCM to control aftermarket electric radiator fan?

[Steel City 06]

I'm tracking you are saying it's a PWM signal I'm seeing. If that's the case though, why does it flip instantly to a hard ground at trigger temp? Also the FSM doesn't mention PWM. Would it be so much slower flashing at room temp ECT that maybe I could see it?

I did just connect a relay with the dim ground and it's enough to trigger the relay FWIW.

Also, the PWM frequency does not change. It is always a fixed value, usually 100 Hz, regardless of fan state.

What is changing is the portion of the grounded signal in each waveform. So with an appropriate RC filter you could actually create a linear DC voltage signal from this.

Very similar to how light dimmers work. Light dimmers simply clip the AC waveform. Doesn't affect the frequency or the voltage, just the proportion of time the bulb is powered. Except for the absolute worst quality bulbs, you generally get no more flicker effect as the bulb is dimmed than it would have at full brightness.

To give an idea how fast you'd have to react to be able to see a change, most fans and ECMs are set to have 1% increments in PWM state. Now, if we assume 100 Hz PWM, that means each waveform is 10 milliseconds in length. So each percentage of PWM state corresponds to 1% of 10 milliseconds, or 100 microseconds. This means you'd need to be able to interpret a change 1/10,000th of a second in length to actually understand the PWM signal. (Hence why you need an oscilloscope that can sample at at least 10,000 Hz to actually interpret the waveform.)

To build on that, that means at 25% fan state, the ground connection is provided for 2.5 milliseconds, followed by an open circuit for 7.5 milliseconds. (Repeat this 100x a second.) To change to say 67% fan state, then ground is provided for 6.7 milliseconds, followed by 3.3 milliseconds of open circuit.

 

[KingCarGuyZ]

No change, but I also checked with the ignition off and I still get the same weak ground?

well if I understand the manual screenshot correctly, "when the coolant temp drops BELOW 209*, the PCM opens the ground bath of the realy" meaning below 209* the circuit is effectivly open or PWM is set to 0%

That "weak ground" you are seeing is very likely a PWM signal, especially if its only seen above 209* (or whatever your set-point is in HPT) This would also co-inside with @hamhawk 's experience. By setting both the hi and low tolerence of the PWM to be 199, he affectively created a switch to ground circuit that enabled the fan above 199, and disables it below.

I would say it looks promising. If you were in the DFW area I would say we could sneak by Uni and borrow an oscilloscope to confirm. The only way I know to be able to tell a PWM signal from a ground is by hooking a PWM fan to it, or via an oscilloscope as @Steel City 06 outlined. I gotta sit down and order parts. Currently diagnosing an A/C issue that might have me up there replacing the condensor anyway.

 

[SkylinesSuck]

I think I understand how a PWM signal would look dim now better, thanks.

I think I might actually have a PWM fan stashed somewhere, but it had an external controller I know is long since gone. Do PWM fans like the Camaro one have an internal controller or something? I'm sure that's earlier in this thread and I just forgot already.

 

[Steel City 06]

I think I understand how a PWM signal would look dim now better, thanks.

I think I might actually have a PWM fan stashed somewhere, but it had an external controller I know is long since gone. Do PWM fans like the Camaro one have an internal controller or something? I'm sure that's earlier in this thread and I just forgot already.

Yes, they have an internal controller and need no relay or switch. Just wire it straight to battery and ground and apply a PWM signal to the tiny 3rd wire. The controller interprets that signal digitally and uses that value to set a target RPM on the brushless motor.

Non-PWM (usually brushed) fans could be used as well, though you'd have to use a huge solid state relay on the power supply. The WJ relay is one common part used for this.

 

[Steel City 06]

Theoretically you could hook up an LED and it might visibly dim and brighten based on the PWM state. You probably won't be able to see 1% resolution, but 25% vs 75% should be pretty obvious for example.

 

[SkylinesSuck]

@hamhawk did you swap your gauge cluster along with the PCM and harness?

Theoretically you could hook up an LED and it might visibly dim and brighten based on the PWM state. You probably won't be able to see 1% resolution, but 25% vs 75% should be pretty obvious for example.

It looked the same at room temp all the way up to just before the trigger temp at 180.

You saw what I said about seeing the weak ground even with the ignition off, right?

 

[Steel City 06]

@hamhawk did you swap your gauge cluster along with the PCM and harness?



It looked the same at room temp all the way up to just before the trigger temp at 180.

You saw what I said about seeing the weak ground even with the ignition off, right?

Yeah, not sure what's up with that. Maybe some residual capacitance?

 

[SkylinesSuck]

I just tried my stock '98 PCM for funsies and got the same full time weak ground, so maybe it's a harness difference or issue? Now that the pin/wire is actually inserted far enough to be connected to the PCM, I'm going to see if it still switches to a hard ground at target temp with the 98 PCM a little later today just so we can know if the capability is there in a JTEC not + version PCM.

 

[SkylinesSuck]

'98 PCM still doesn't trigger any change in the ground on pin C2 So it looks like this is a JTEC+ option only maybe?

 

[KingCarGuyZ]

@hamhawk @SkylinesSuck

-just shipped a fan and want to play around with this. anyway ya'll could upload the files you are using or point me in a good direction for a baseline XJ/WJ file? also how did ya'll go about adding the pin to C-21? is there a good place to buy pins (I'm assuming its similar to your standard Deutsch connector)

 

[SkylinesSuck]

Busy right now, but remind me if I don't get back before the end of the weekend. On the re-pinning, I scored a used harness and cut it up. Used will work fine as it's plastic bits in the connector that hold everything in place.

 

[SkylinesSuck]

Okay, so like I said, the pinning part is pretty easy. If you pull off the PCM connector and look at the sides of it, there is a little light blue tab visible through holes on either side of the connector. It locks the pins in place. Simply slide it a little to unlock the pins and push yours through the backside then lock it back in. Do NOT disassemble the entire connector. It is EXTREMELY challenging to get all the pins lined back up to put it back together and it's entirely unnecessary. Ask me how I know

 

[SkylinesSuck]

Oh yeah, and on the XJ file, I think I downloaded the stock file I pulled from my spare XJ JTEC+ PCM. I'll try to get on my laptop and take a look. It will be a .hpt file of course.

 

[SkylinesSuck]

@hamhawk @SkylinesSuck

-just shipped a fan and want to play around with this. anyway ya'll could upload the files you are using or point me in a good direction for a baseline XJ/WJ file? also how did ya'll go about adding the pin to C-21? is there a good place to buy pins (I'm assuming its similar to your standard Deutsch connector)

I had to change the file extension to .txt to get it to upload, but it's a .hpt file you just need to relabel.

 

[Steel City 06]

I had to change the file extension to .txt to get it to upload, but it's a .hpt file you just need to relabel.

@Chris

Maybe it'd be worth enabling filetypes ending with .hpt (HP Tuners tune) and .hpl (HP Tuners log file) site-wide?

As to how they're produced I think they are just compressed and encrypted from the original .bin files so that people can't reverse engineer the software. So I doubt there's anything really executable in them.

 

[Chris]

@Chris

Maybe it'd be worth enabling filetypes ending with .hpt (HP Tuners tune) and .hpl (HP Tuners log file) site-wide?

As to how they're produced I think they are just compressed and encrypted from the original .bin files so that people can't reverse engineer the software. So I doubt there's anything really executable in them.

Thanks for tagging me. I enabled .hpt file uploads!

 

[ColoJeep]

Thanks for tagging me. I enabled .hpt file uploads!

I don't know a damn thing about I.T. , but it's great for people to be able to share information . Thanks Chris !

 

[KingCarGuyZ]

I had to change the file extension to .txt to get it to upload, but it's a .hpt file you just need to relabel.

you peoples and your autos lol. gotta go find a manual one.

great for reference though, much appreciated.

 

[SkylinesSuck]

I take great offense to that insult! I will row my own gears till I die! I took that one and made it manual. Well, I made it not throw any codes anyways. Do you want the version I tweaked? I am probably the least familiar with the software and tuning as any person in this discussion, so I'd be hesitant to copy my work, but you are welcome to it!

 

[KingCarGuyZ]

View attachment 655324

I take great offense to that insult! I will row my own gears till I die! I took that one and made it manual. Well, I made it not throw any codes anyways. Do you want the version I tweaked? I am probably the least familiar with the software and tuning as any person in this discussion, so I'd be hesitant to copy my work, but you are welcome to it!

sure - this is my first time doing tuning that doesn't involve a screwdriver. i thought manual was one of the few things you couldn't do to these tunes.

and I agree. autos better on paper but I will keep my 5-spd.