Coolant temp fluctations & thermostat timing ??

[Truck Fun]

Been somewhat watching this for a while but now trying to be more detailed. My 2021 has more coolant temp fluctuations and runs hotter than when I had my 2018. Today I was driving 4-lane about 67mph, then some in-town errands with a few stop lights, then back on the 4-lane. Outside temp as per truck was 84. At about 5 miles back on the 4-lane, my temps were:
Coolant 212/213
Trans 188/190
Oil 219/221
After about another 10 miles, the coolant temp quickly dropped down to about 203/204 and then shortly worked back up to 208/210; which to me would be the thermostat opening & closing. But is it normal for that not to occur until the 212/213 range? And one warm day this summer I recall around a 215 at one point (55-60mph, 2 lane road, some flat and some rolling).
Also, I've notice that if I've been driving for a while, then stop and shut off the engine, then start it again within 5-10 minutes, the coolant temp will show at start-up as high as 217-221 but immediately drop to a 204-210 range. I don't recall ever seeing that happen on my 2018.
Any thoughts on how the system is operating?
Thanks.

 

[crazykid1994]

203 is the thermostat setting and the ags will dictate actual temp as it opens and closes. That seems normal

 

[Truck Fun]

203 is the thermostat setting and the ags will dictate actual temp as it opens and closes. That seems normal

So do the thermostat and ags open/close in conjunction or do those act separately?

 

[crazykid1994]

Your thermostat is separate from the ags. Like any vehicle the thermostat has a temp where it starts to open. Factory is 203°. The ags is programmed to certain computer controlled functions not limited to transmission temp, ac on/off, coolant temp. The ags has a set of points it must hit before it opens or closes. The thermostat is only related to coolant temp and is not connected to the computer. The thermostat may be wide open but the temp will stay higher if the ags stays closed. Quite a few of us have removed parts of the ags fins or fully removed the ags for performance reasons. Overall functionality there is no downfall to the ags being there. It just keeps temps higher and the truck tends to warm a bit faster on cold mornings since the air is being blocked.

 

[mnkworkstation]

I have been watching your post for a while and I have a question here. I have a 2013 Ram with an efan, my fan only turns on with AC on, it will ran hot without AC on. I see I have constant 12V to the fan, I also see a green wire on the connector to the fan, is that what the ECU uses to activate the fan? what can I do to make my fan fan kick in. I donot have any temperature related codes in the ECU. What can I look out for since fan activation does not directly depent on the coolant sensor? Any help?

 

[CunningStunt]

I have been watching your post for a while and I have a question here. I have a 2013 Ram with an efan, my fan only turns on with AC on, it will ran hot without AC on. I see I have constant 12V to the fan, I also see a green wire on the connector to the fan, is that what the ECU uses to activate the fan? what can I do to make my fan fan kick in. I donot have any temperature related codes in the ECU. What can I look out for since fan activation does not directly depent on the coolant sensor? Any help?

I am not 100% cerrtain, but if you put the efan in aftermarket in place of the fan clutch, you need to tune it to activate the fan in conjuction with the temp sensor.

 

[mnkworkstation]

I dont have clutch on my fan, its just efan and I think that is how this Ram came in.

 

[crazykid1994]

3.6 was efan only. May have a bad sensor or failed 2 speed relay. Not sure on troubleshooting that though do not much help.
Edit: actually the 2013 is computer controlled speed which you are correct. The temp sensor on the fan may be having an issue. Not sure is. I’m not sure how to troubleshoot the PWM fans.