Overheating! Radiator fan keeps shutting off randomly. Help!!!

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DLiT

New member
Rad Fan has been shutting off randomly causing me to overheat. Fan motor was pretty rusted so I replaced it, along with the thermostat and ECT. I check the low speed relay and fuse, they’re fine. Checked the high speed relay, it’s also fine. Why is my Fan still turning on and off?


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Was the relay checked WHILE the fan wasn't working? Because they can get hot and work intermittently. Your symptom really is consistent with a failed relay. Only other thing I can think of is if the concern only occurs with AC on, and somewhere within that circuit something is allowing a temporary open circuit.
 
Since this is about the 4th question in the last week about radiators and coolant does everyone understand that u can't use regular anti-freeze in the jk's they are specific to the model year! Now to answer the OP question it sounds like u have a clog in the system, and it's not kicking on the fan, or the temp sensor\pressure sensor is bad.
 
I just flushed the whole coolant system, put in fresh HOAT and I ALSO replaced the ECT.....


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DLiT said:
Rad Fan has been shutting off randomly causing me to overheat. Fan motor was pretty rusted so I replaced it, along with the thermostat and ECT. I check the low speed relay and fuse, they’re fine. Checked the high speed relay, it’s also fine. Why is my Fan still turning on and off?


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dpetersen1988 said:
Since this is about the 4th question in the last week about radiators and coolant does everyone understand that u can't use regular anti-freeze in the jk's they are specific to the model year! Now to answer the OP question it sounds like u have a clog in the system, and it's not kicking on the fan, or the temp sensor\pressure sensor is bad.
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What.....?
 
I tested both the HSR and the LSR, both are good. What’s next


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Did you check for a clogg in the system? Take the radiator cap off and do a pressure test? Take the inlet cap off and make sure its not clogged.Check for any wires that were cut or touching each other, u could have a short.

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*Update:
The high speed relay kicks the fan on at 222 degrees. However, the low speed relay doesn’t. The relay is good, and I tested the TIPM without the relay to ensure I was getting 12v to relay terminals 85 & 86. I then applied 12v directly to terminal 87 but nothing happens. I unplugged the fan’s upper wiring harness and did a continuity check between the harness and terminal 87 and it was good. Now I’m super confused! That wiring harness AND the fan are brand new...


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DLiT said:
*Update:
The high speed relay kicks the fan on at 222 degrees. However, the low speed relay doesn’t. The relay is good, and I tested the TIPM without the relay to ensure I was getting 12v to relay terminals 85 & 86. I then applied 12v directly to terminal 87 but nothing happens. I unplugged the fan’s upper wiring harness and did a continuity check between the harness and terminal 87 and it was good. Now I’m super confused! That wiring harness AND the fan are brand new...


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Sounding like the issue is in the ground side of the circuit maybe. Do you have a wiring diagram handy? Find out where the common grounds are for that circuit and make sure they're clean and tight. Seems like you've checked everything else.
 
Been searching google and the forums High and Low for a radiator fan circuit that applies to my ‘08 Wrangler, no luck. I’ll check the terminals and grounds and clean them up really good


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DLiT said:
Been searching google and the forums High and Low for a radiator fan circuit that applies to my ‘08 Wrangler, no luck. I’ll check the terminals and grounds and clean them up really good


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You could also backprobe the ground circuit on the fan and manually ground it to see if it kicks on just to see if that's the issue.
 
Correction**

Terminal 85 and terminal 30 on K11 (Low Speed Relay) of the TIPM are showing continuity to the positive battery terminal, and even if the Jeep is off they show a constant 12v hot. There is a Blue wire w/ Green Stripe that runs into the fan’s upper wiring harness. This is the 12v + from the K11 Low Speed Relay, and it has continuity with terminal 87 (the switched 12v+ from K11).

I applied 12v directly to terminal 87 without the relay, and the fan did not kick on in low speed, or at all. I had a solid continuity check between terminal 87 and the plug of the fan’s upper wiring harness. The fan and wiring harness are brand new, perhaps that little coil & resistor behind the upper harness (inside the fan shroud) is bad?
 
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DLiT said:
So terminal 85 and terminal 30 on K11 of the TIPM are showing continuity to the ground/negative battery terminal. Also,the black wire going into the plug of the fan’s upper wiring harness is reading continuity to ground. Does this make sense?


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Sounds like ground circuit is good. Hope it's not the tipm itself. Those things commonly fail.
 
DLiT said:
So terminal 85 and terminal 30 on K11 of the TIPM are showing continuity to the ground/negative battery terminal. Also,the black wire going into the plug of the fan’s upper wiring harness is reading continuity to ground. Does this make sense?


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RELAY-RADIATOR FAN


Harness Family:TIPM_Internal
Cavities:4
Color:NA
Gender:MALE
Part Description:RELAY_MICRO
Engineering Name:Rly_Rad_Fan_K11
Connector No:D838
Option:Standard
PinCircuitWire ColorGauge/SizeFunction
30A16INTERNAL0FUSED B(+)
85A16INTERNAL0FUSED B(+)
86N201INTERNAL0LOW SPEED RAD FAN CONTROL
87N23INTERNAL0LOW SPEED RAD FAN CONTROL

RELAY-RADIATOR FAN


Harness Family:TIPM_Internal
Cavities:4
Color:NA
Gender:MALE
Part Description:RELAY_MICRO
Engineering Name:Rly_Rad_Fan_K11
Connector No:D838
Option:Standard
PinCircuitWire ColorGauge/SizeFunction
30A16INTERNAL0FUSED B(+)
85A16INTERNAL0FUSED B(+)
86N201INTERNAL0LOW SPEED RAD FAN CONTROL
87N23INTERNAL0LOW SPEED RAD FAN CONTROL



215473984


215444296
 
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