Is this the work around for keeping the coolant temperatures down with a PWM fan.

[Yardbird]

Could a simple wiring change help keep the engine temperatures cool?

I really dislike (hate) the wide range of temperatures that are allowed with our engines. Just because the engineers will allow the engine temperatures to range from mid 190s to mid-upper 220's and quickly back is ridiculous. There is no excuse available that makes sense for this as far as being good for the engine.

I have been planning for the last three years to put a pusher ran on to help with cooling, but I have ran onto an article that may make that unnecessary.

According to what I have found, the dark blue/gray wire going to the fan is the wire that controls the fan speed. If that wire is grounded, the fan will revert to highest speed.

I could see running an extra wire to that wire, back to a nice on/off switch in the dash, then turning it on when the coolant temperature gets high.

Last week, I went back up to Beech mountain again. At any time of year, I have never been up that road where the temps didn't get to mid 220s, then when hitting the top, very quickly cools back down, too quickly in my opinion.

The mountain is steep, long, full of switchbacks, I'm in first gear a lot of the time because of the steep, sharp, curves.

I'm posting a schematic of the wiring. Has anyone tried this? I'm unable to do any investigative work myself right now, as I'm housebound in a wheelchair for a while.

 

[Mojo88]

2018..... I believe your PCM is unlocked. So simply buy the HPTuners dongle and bypass cable, then adjust the fan settings in the tune. And also install a 180* stat. That should get your cruise ECT ~185* even without fan coming on. If you indeed have PWM fan, set at 190* in the tune, then max temps (at slower speeds and stops) will briefly hit ~197*, and quickly drop down once AGS open and fan comes on.

Controlling the fan with a manual switch would be one giant PITA IMHO........ plus you'd have to 100% confirm that your switch opens the AGS.

 

[Yardbird]

Everything I read claims my truck has a locked PCM, and would also require a bypass cable. If a simple switch and wire will do what I want, I'm OK with that.

 

[Mojo88]

Ahhhh, if locked PCM, then it would cost a lot more.....
I have no idea about the switch.
Good luck with the mod!

 

[Yardbird]

What I'm wanting to do, and how I've mentioned doing it, must be correct. AI said that was how it is done. lol

What AI didn't tell me, is if grounding that wire will burn up the board that operates all that stuff.

I do know the fan kicks on with the A/C, but, the speed of the fan is dependent upon head pressure in the A/C system. The fan may be running fast, very slow, or not at all, according to how much pressure the system has built up.

I have experimented with the A/C on, and the fan speed is all over the place. The only way to modify that is is run a jumper wire and switch to the A/C pressure switch to mimic high pressure to trick the fan into running on high.

 

[Mojo88]

....I do know the fan kicks on with the A/C, but, the speed of the fan is dependent upon head pressure in the A/C system. The fan may be running fast, very slow, or not at all, according to how much pressure the system has built up......

Interesting, I knew fan came on with A/C, but I woulda thought PWM fan would adjust speed based on ECT.

I'll be curious to see if anyone here has ever done it your way. Regardless, I would advocate extreme caution, lest you cause extreme damage!!

 

[Yardbird]

Interesting, I knew fan came on with A/C, but I woulda thought PWM fan would adjust speed based on ECT.

I'll be curious to see if anyone here has ever done it your way. Regardless, I would advocate extreme caution, lest you cause extreme damage!!

If my truck ends up bricked, you will know the dark blue/gray wire wasn't the way to go...lol

I suspect it will be several weeks or longer before I'm able to get out and work on it.

The new front rotors, then the next day oil change, along with other outside chores, plus a drive and day out in the mountains, set off another bad flare that sometimes takes months to resolve.

 

[crash68]

What I'm wanting to do, and how I've mentioned doing it, must be correct. AI said that was how it is done. lol

What AI didn't tell me, is if grounding that wire will burn up the board that operates all that stuff.

First tip, AI isn't all it's cracked up to be. Best to fact check it.
As for grounding the wire to make the fan go 100%, there's probably a 33.3% chance that might work. If the fan is looking for a positive or changing signal then grounding won't do anything.
As for burning up the ECM, unless you apply powe that shouldn't be therer to the wire for the fan speed signal it shouldn't cause any harm. Also if the alternative wiring for the fan speed signal is done correctly the ECM will be isolated from whatever signal you manually try to run the fan with. To do this use a SPDT switch to select the ECM or alternate speed signal.
Before making any permanent changes it's probably best to make temporary connections to test your grounding theory.

Given your concern of acceptable engine operation temperatures, you should probably consider having the ECM unlocked then use something like HP Tuner to adjust the engine cooling parameters to your liking. This will result in smoother more consistent temperature control rather than running the "risk" of getting warmer than you like then overcooling or overheating

 

[Mojo88]

......The new front rotors, then the next day oil change, along with other outside chores, plus a drive and day out in the mountains, set off another bad flare that sometimes takes months to resolve.

Ahhhh, for this I DO have a good suggestion. FIND A GREAT CHIROPRACTOR!!
I have one, and he's a damn miracle worker, haha...........

 

[Yardbird]

Mine is Psoriatic Arthritis that gets in my feet and knees. I've been in a wheelchair since last Friday night (6/13). Looks like it may go on another few weeks or more. This is a bad flare. My inflammatory markers were off the charts when I had bloodwork Tuesday.

 

[04fxdwgi]

PWM fans actually have the controller built into the motor. What controls the fan speed is a "signal voltage (not to be confused with line voltage) " from the PCM, telling the PWM controller what to do. Question is, is the PWM sending the signal to be controlled in the PCM or the PCM sending the signal.

Grounding that signal line may convert your PCM into a paper weight.

What may work, is injecting a false signal (what ever that is) into the PWM input terminal on the motor AFTER it has been disconnected from the PCM.

Not cheap, but much easier to go with HP Tuner / unlocked PCM / security bypass cable route.

Or, probably the cheapest and most reliable method and way I would go, just install an aftermarket fan controller that operates on an adjustable coolant temp setpoint and an A/C and/or switch forced bypass on.

 

[Mojo88]

......Or, probably the cheapest and most reliable method and way I would go, just install an aftermarket fan controller that operates on an adjustable coolant temp setpoint and an A/C and/or switch forced bypass on.

Just curious, have you seen one of these devices installed in a RAM with a PWM fan? Also, will this open the AGS, or must some fins be removed?

Thanks

 

[crash68]

Question is, is the PWM sending the signal to be controlled in the PCM or the PCM sending the signal.

PWM is the type of signal used to control the speed of the motor, typically you can use a meter that is capable of frequency or duty cycle to determine approximately how fast the controller (ECM in this situation) wants the motor to spin.
The cooling fan isn't sending out any signals but the ECM is most likely capable of detecting an open or short of the control wire to the fan and register an error code.

will this open the AGS, or must some fins be removed?

an aftermarket fan speed controller most likely will not open the AGS, the fins will need to be removed.

 

[04fxdwgi]

Just curious, have you seen one of these devices installed in a RAM with a PWM fan? Also, will this open the AGS, or must some fins be removed?

Thanks

There are a couple of controllers out there that work on a PWM fan. Just haven't seen one on a Ram specially.

Forgot about the AGS component, as I completely removed mine a couple of years ago and it didn't enter into the equation..

 

[RamDiver]

PWM is the type of signal used to control the speed of the motor, typically you can use a meter that is capable of frequency or duty cycle to determine approximately how fast the controller (ECM in this situation) wants the motor to spin.

I liked your idea of using a SPDT switch to isolate the ECM. I had been thinking of using a relay to accomplish the same, but I'm sure the switch would be simpler and adequate.

I understand certain multimeters have the capability of decoding the PWM signal, but an oscilloscope would be far more practical for this project.

I have no experience using the following product, but there are many like it, and it would be a far more cost-effective method to allow scoping the signal for precise results.

https://www.amazon.com/Hantek-Digital-Oszilloskop-Storage-Oscilloscope/dp/B0728HBNDV/ref=sr_1_4?dib=eyJ2IjoiMSJ9.t22gzDxDuteUjD86KZYLyN4UEhH3nipt9ZvhM8Rq3PC2RwjahDMTmXJNaVLM3rPXYMmjkWEA5JXey-7Mdg3kcQEiP9wjuOlYTTMpvB8j03PfJPx3CS4f8s6gDr-2IP6i-359eTD4Nzza6UN9geSEegvAD7bSg6I85v_aEYCKNvrlAZrube7vU4K0u3LPI31XTWaKNLbPVEXPERJiw9Ks6pLEjWw66tZ2Ru_WfEGRtgQ.MQ4Bn3NchKIuhth-ukVonmhQ8eYicEHVN6Y4tfVvCe0&dib_tag=se&keywords=laptop+oscilloscope&qid=1750607761&sr=8-4

.

 

[crash68]

I understand certain multimeters have the capability of decoding the PWM signal, but an oscilloscope would be far more practical for this project.

About the only practicality for using an oscilloscope over a meter, is being able to buy a cheap one on Amazon like you referenced if one doesn't own a meter that does frequency or duty cycle. I have four such meters, including a Fluke 116 that is capable of frequency over 1kHz. That's plenty to determine if there's a viable signal for the fan to run. If the project involved calibration to very specific frequencies then a scope would work better (yes I have a scope too!).
As for isolation of the signals, a SPDT switch or relay are the simpler methods. A diode could be used but it will need to be biased correctly depending on the PWM signal provided it doesn't completely change polarity.