Radiator Fan Wiring / Radiator Fan Relay

[John Schmidt]

Hello all. On my 2020 Ram 1500 Bighorn w/5.7 I'm looking at the radiator fan motor. There are 3 wires going to the motor, 2 are like 10 gauge, red for positive, black for negative, and then there's like a 22 gauge, green wire, that you almost can't see unless you're looking for it. Does anyone know EXACTLY what this thin green wire is used for? Has anyone put a DVM on these 3 wires during fan operation. Maybe Pulse Width Modulation??
Further, I could NOT find a Radiator Fan RELAY in the truck - there is a radiator fan fuse, but no relay to be found. Nothing shown on inside cover of fuse/relay cover in engine compartment. I called TWO Ram dealers, talked with parts, and neither of the parts guys could come up with a part number and/or location for a radiator fan relay.
Has anyone done any exploration into the operation of the radiator fan?
Backstory - I'd like to be able to manually control the radiator fan, perhaps turn it on a bit earlier than what seems like the 226F default setting.
No, I don't want to spend $600+ for a tune/pcm swap, nor do I want to fake out the computer by putting a resistor in parallel with the ECT sensor.
Any ideas/thoughts or better yet schematics w/labels?
Thanks.
John

 

[SoFLRam]

Green wire is computer signal. Turn fan off / low speed/ high speed

 

[John Schmidt]

Hi. Yes, so far I've been able to determine it's a Pulse Width Modulation signal coming from the computer ... I'm going to have to build a PWM module with a 555 timer. Might put an oscilloscope on it to observe the signal. First project for this summer. Thanks for your response!

 

[SoFLRam]

Yes. Im having trouble with mine right now.

 

[Wild one]

Hi. Yes, so far I've been able to determine it's a Pulse Width Modulation signal coming from the computer ... I'm going to have to build a PWM module with a 555 timer. Might put an oscilloscope on it to observe the signal. First project for this summer. Thanks for your response!

Get ahold of CrazyKid,he might have some insight for you.

Pwm controller/v6 electric fan install

alright so instead of blowing up a different thread I’m starting my own. I installed the v6 electric fan in my truck and installed a pwm controller to run the fan so at idle the fan doesn’t cycle on and off. That gives me better cooling characteristics due to constant air flow across the...

www.ramforum.com

 

[crash68]

Does anyone know EXACTLY what this thin green wire is used for? Has anyone put a DVM on these 3 wires during fan operation. Maybe Pulse Width Modulation??

The Gen5 trucks started using a PWM fan that's controlled from the ECM. It was the same fan set up the Gen4 EcoDiesel uses, the Red and Black wires go to the battery, at full load the motor draws 72 amps.
The fan speed should ramp up based on coolant and transmission temperature along with pressure/temperature signal from the AC.
The fan should start ramping in before 220° and if you use a good full synthetic oil the engine will be fine with what some perceive as high temperatures.

 

[SoFLRam]

Problem is 252°. Mine runs 185° to 225° most days, but it still shoots up sometimes.

 

[John Schmidt]

Wow. Thanks for another great response. My truck's oil temp shoots up occasionally to 225-230. I never two or haul anything, just me driving around. I wouldn't mind being able to have the fan turn on at maybe 210F or so. I use Red Line, so yes, probably all is fine - I still, just don't like temps past 210. Maybe if I have too many other projects to think about, I'll just let it go, but it really would be a fun one ....
Thanks again!
John

 

[Wild one]

Wow. Thanks for another great response. My truck's oil temp shoots up occasionally to 225-230. I never two or haul anything, just me driving around. I wouldn't mind being able to have the fan turn on at maybe 210F or so. I use Red Line, so yes, probably all is fine - I still, just don't like temps past 210. Maybe if I have too many other projects to think about, I'll just let it go, but it really would be a fun one ....
Thanks again!
John

Have you ever considered a colder thermostat.You could stick a 190,or even a 180 in it and see how it pans out.They're pretty easy to swap,so if you decide you don't like a colder thermostat you can always stick the stock 203 back in it.After 2016 they started to use coolant to heat the oil,and supposedly help cool it once it's at operating temp,so on paper a colder thermostat should help slightly with high oil temps.

 

[John Schmidt]

Hi. Thanks. Yes, I've tried a thermostat that opens earlier (192 v 203 stock) ... but ultimately to no avail. It seems that once the thermostat starts to open and mix in that cooler water from the radiator, both masses of water start rising together. So the thermostat is wide open, perhaps a little earlier, but the cooling capacity of the radiator is somewhat depleted, so the whole mass of coolant starts going up. Again, I'm sure this is all well within the specs that the design calls for, so pretty sure nothing too bad is going on, but in my training and background sometimes cooler can be a little better - like if I could keep things at 203 (the stock thermostat temp), I'd be a little happier.
Thanks.
John

 

[Wild one]

Hi. Thanks. Yes, I've tried a thermostat that opens earlier (192 v 203 stock) ... but ultimately to no avail. It seems that once the thermostat starts to open and mix in that cooler water from the radiator, both masses of water start rising together. So the thermostat is wide open, perhaps a little earlier, but the cooling capacity of the radiator is somewhat depleted, so the whole mass of coolant starts going up. Again, I'm sure this is all well within the specs that the design calls for, so pretty sure nothing too bad is going on, but in my training and background sometimes cooler can be a little better - like if I could keep things at 203 (the stock thermostat temp), I'd be a little happier.
Thanks.
John

The later trucks with the supposedly oil heater/cooler do seem to run hotter oil temps then the earlier trucks with-out it.Wonder what would happen if you removed it from the mix,by disconnecting the hoses to it. I know with dual remote filters on my truck that doesn't have the cooler with a 180 t-stat,i have to really be beating on it to get the oil temps above 205.

 

[John Schmidt]

Interesting ... I might have to do a little experimenting. I'd like to do the oil filter relocation also, even if just to make changing the filter easier and with less of a mess. Thanks for the ideas/thoughts.
John

 

[Wild one]

Interesting ... I might have to do a little experimenting. I'd like to do the oil filter relocation also, even if just to make changing the filter easier and with less of a mess. Thanks for the ideas/thoughts.
John

Relocating the filter was probably one of the best mods i did,i don't mind changing oil now,lol. I started with a single remote filter,then went to the dual set-up with the bigger older style 30-8 filters that use a 3/4-16 thread pitch filter.I picked up a couple psi with the dual set-up,and my oil temps also dropped a good 5 degrees compared to the single set-up,while gaining more oil capacity.Only downside is having to buy 2 filters and about 8 litres of oil to do a change.
First set-up.

 

[John Schmidt]

Wow, very nice. What brand/model of single oil filter relocation is/was that? Another project to add to my list!! With the dual setup are the two filters in parallel or series? I'm not sure that I understand how the increase in PSI occurs. Do you have a theory and if yes, can you explain? Thanks VERY much.
John

 

[crazykid1994]

Also is there active grill shutters? That won’t let the temps go lower even with the lower tstat. If there is you should look into removing a few slats to let more airflow to the radiator. I don’t think your idea for the pwm module will work how you want. Also is your truck have the heavy tow package?

 

[John Schmidt]

Hi. Yes, I have already removed all slats except top, bottom, and middle (ags drive). What pan module. No towing package. Thanks!
John

 

[crazykid1994]

Hi. Yes, I have already removed all slats except top, bottom, and middle (ags drive). What pan module. No towing package. Thanks!
John

I meant pwm. Sorry. The cheaper pwm module most likely won’t put out the right signal and I’m not sure how you plan on commanding it for the coolant temp and ac line pressure. The fan is variable speed and if it doesn’t run low speed below 226° you may have another issue or something’s not calling to turn the fan on. 220° I think is the factory over heat setting which should kick the fan to high

 

[John Schmidt]

Hi. Good questions. My plan (emphasize plan) at this point is to use a temperature sensor (mounted perhaps to radiator or to thermostat housing). The temperature sensor has a resistance which goes down as temperature goes up. This resistance value will be used in the pwm circuit using 555 timer shown below (everything inside the dashed lines is the 555 timer chip). The circuit is an example, although not necessarily the exact circuit I will use. The temp sensor will be part of the R1 value (along with a variable resistor) which will change the duty cycle of the pwm output (orange box, pin 3 of 555) signal. Higher duty cycle will give higher fan speed. I haven't yet started the actual design and I will base it in part on what I observe when examining the PWM signal currently supplied to the stock fan, with an oscilloscope. Guessing around $25 - $50 in parts including temp sensor. In addition, I still have to figure out what to do with the existing PWM signal. This is a project/experiment but who knows, it might work! Thanks.
John

 

[crazykid1994]

Hi. Good questions. My plan (emphasize plan) at this point is to use a temperature sensor (mounted perhaps to radiator or to thermostat housing). The temperature sensor has a resistance which goes down as temperature goes up. This resistance value will be used in the pwm circuit using 555 timer (everything inside the dashed lines is the 555 timer chip). An example, although not necessarily the exact circuit I will use is shown below. The temp sensor will be part of the R1 value (along with a variable resistor) which will change the duty cycle of the pwm output (orange box, pin 3 of 555) signal. Higher duty cycle will give higher fan speed. I haven't yet started the actual design and I will base it in part on what I observe when examining the PWM signal currently supplied to the stock fan, with an oscilloscope. Guessing around $25 - $50 in parts including temp sensor. In addition, I still have to figure out what to do with the existing PWM signal. This is a project/experiment but who knows, it might work! Thanks.
John

View attachment 517947

You still need to read ac line pressure

 

[John Schmidt]

Yes, especially if I want the fan to turn on when the AC is on. Still thinking about that one ...
Thanks for mentioning it though.
John