Electric Radiator Fan Not Working

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jerbo1978

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Earlier today the digital temp Guage stayed at 100°
And the analog temp Guage went to zero.
Check engine light came on along with the red lightning bolt alert light and the 4 wheel drive service light.
3 codes popped up
P0481....p0118...2181
The truck is making me crazy
 

RamDiver

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Earlier today the digital temp Guage stayed at 100°
And the analog temp Guage went to zero.
Check engine light came on along with the red lightning bolt alert light and the 4 wheel drive service light.
3 codes popped up
P0481....p0118...2181
The truck is making me crazy

LOL, I have yet to read that in any of your reports, before now.

You've been exceptional at providing details until now. Are there any more features on your truck that we should know about? :)

.
 
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jerbo1978

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No more features..
Those codes popped up do to me messing with the temp sensor connector...
 
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jerbo1978

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@RamDiver Reason I didn't mention the codes earlier is because I think they were activated because of the temperatures not reading on the analog Guage and the info center
 

RamDiver

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I'm previously engaged today and not available until later tonight or tomorrow. Have a great day and check out that relay #2. I've posted details about it above.

Apparently, it receives a ground from the pcm. :cool:

.
 
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jerbo1978

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Leave no stone unturned when chasing electrical demons. :cool:




Could you please provide a closer picture of that connector? Try carefully moving the red cap up first but be careful that the wires don't disengage from the bottom section.

I may be wrong but, if that's the type of connector it appears to be, slide the red cap up, and the wires may just pop off the receptacles.

Clean up the wire ends (cut and restrip if necessary, pay attention to stripped wire length), re-insert them into the receptacle, and press the red cap down on top again.

Take a pic first to capture the wire positions before disassembly.

.
@RamDiver,
I've got some more info on that fan not working.
I tested the high speed relay which is located on the top of the rad support bolted on the bracket with the horns.
The big red wire with brown stripe that comes from rad fan low relay pin 30 in the Tipm has 14v with AC on or off...
Smaller wire that is brown with lt blue stripe which comes from Rad relay coil signal is also 14v with AC on or off...
The small brown wire with the orange stripe which comes on when run relay is energized is also reading 14v AC on or off...
The Big dark green wire with the blue stripe has no voltage with AC on or off....
The fan plug is 2 connector
The female supply plug to the fan is 3 connector.
The bottom connection which has no place to go is reading 14v when AC is activated.
The top two are a green with blue stripe which has zero power and a black ground...
Any Ideas would be great20230525_200714.jpg
 

RamDiver

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LOL, they're just trying to mess with your head. :cool:

Both relays are tied to the B+ (12 v) and the circuit board pulls the other side of the relay coil to ground and energizes the relay.

So remember we're looking for a potential difference to energize the relays. Place the positive lead of the multimeter on the always hot side, feeding the relay and the negative lead on the circuit board side of the relay.

When the circuit board pulls that terminal to ground, you will then have a potential difference across the relay coil and it will be energized. And you will read 12 volts across the relay coil as apposed to reading on both sides wrt chassis ground.

If the circuit board doesn't pull the terminal to ground, you will not see a 12 V potential across the coil.

It's all about where you're referencing ground. If you use chassis ground as the reference, you will see 12 V on both sides of the relay coil because the coil passes DC from the always hot side.

At least until the circuit board pulls one side to ground. Then, only the always hot side of the coil will have 12 wrt to chassis ground.

Does that make sense?

In one of my previous posts, I identified that the PCM applied a ground signal to one side of the coil. That was the important part of that post.

Let me know if that's clear or not. :cool:

.
 
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dannyloski

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LOL, they're just trying to mess with your head. :cool:

Both relays are tied to the B+ (12 v) and the circuit board pulls the other side of the relay coil to ground and energizes the relay.

So remember we're looking for a potential difference to energize the relays. Place the positive lead of the multimeter on the always hot side, feeding the relay and the negative lead on the circuit board side of the relay.

When the circuit board pulls that terminal to ground, you will then have a potential difference across the relay coil and it will be energized. And you will read 12 volts across the relay coil as apposed to reading on both sides wrt chassis ground.

If the circuit board doesn't pull the terminal to ground, you will not see a 12 V potential across the coil.

It's all about where you're referencing ground. If you use chassis ground as the reference, you will see 12 V on both sides of the relay coil because the coil passes DC from the always hot side.

At least until the circuit board pulls one side to ground. Then, only the always hot side of the coil will have 12 wrt to chassis ground.

Does that make sense?

In one of my previous posts, I identified that the PCM applied a ground signal to one side of the coil. That was the important part of that post.

Let me know if that's clear or not. :cool:

.
Could you elaborate a bit more on this?

I’m trying to diagnose why my electric fan is not engaging when A/C is on, as it should. Came across this thread and trying to understand the process you’re explaining here.

While I’m not throwing any CEL codes like the OP, I do have similar issues. I tested all fuses with a multimeter and they’re good. I checked continuity from the fan plug to the rad support relay and it’s good. I tested continuity from rad support relay wires to the green plug at the TPIM, all good. I tested the rad support relay (per this guide) and supposedly it’s good. Not sure what the problem is. If I jump the rad fan relay, the electric fan works.

I don’t want to just throw money at it replacing parts, so trying to troubleshoot and find the culprit.
 

Wild one

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Could you elaborate a bit more on this?

I’m trying to diagnose why my electric fan is not engaging when A/C is on, as it should. Came across this thread and trying to understand the process you’re explaining here.

While I’m not throwing any CEL codes like the OP, I do have similar issues. I tested all fuses with a multimeter and they’re good. I checked continuity from the fan plug to the rad support relay and it’s good. I tested continuity from rad support relay wires to the green plug at the TPIM, all good. I tested the rad support relay (per this guide) and supposedly it’s good. Not sure what the problem is. If I jump the rad fan relay, the electric fan works.

I don’t want to just throw money at it replacing parts, so trying to troubleshoot and find the culprit.
Are you checking it after driving the truck for awhile to get it up to operating temp,and then turning the A/C on high.Techinically it should kick the fan on even when the trucks cold,but i ran into a 3rd gen that had to be close to operating temp,before the A/C would cycle the electric fan.
 

dannyloski

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Are you checking it after driving the truck for awhile to get it up to operating temp,and then turning the A/C on high.Techinically it should kick the fan on even when the trucks cold,but i ran into a 3rd gen that had to be close to operating temp,before the A/C would cycle the electric fan.
Yeah, neither at operating temp nor cold will the electric fan turn on.
 

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Could you elaborate a bit more on this?

I’m trying to diagnose why my electric fan is not engaging when A/C is on, as it should. Came across this thread and trying to understand the process you’re explaining here.

While I’m not throwing any CEL codes like the OP, I do have similar issues. I tested all fuses with a multimeter and they’re good. I checked continuity from the fan plug to the rad support relay and it’s good. I tested continuity from rad support relay wires to the green plug at the TPIM, all good. I tested the rad support relay (per this guide) and supposedly it’s good. Not sure what the problem is. If I jump the rad fan relay, the electric fan works.

I don’t want to just throw money at it replacing parts, so trying to troubleshoot and find the culprit.

Hi Danny, I was scanning this thread with my phone trying to get a clear picture again, I believe that I have it sorted out again.

What exactly are you looking to clarify? The schematic on post #29 from the previous page shows 2 fan relays that are triggered by the BCM, IIRC.

Please explain what portion you would like clarified.

Do you have an accurate schematic diagram?

.
 

dannyloski

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Hi Danny, I was scanning this thread with my phone trying to get a clear picture again, I believe that I have it sorted out again.

What exactly are you looking to clarify? The schematic on post #29 from the previous page shows 2 fan relays that are triggered by the BCM, IIRC.

Please explain what portion you would like clarified.

Do you have an accurate schematic diagram?

.

I’m trying to understand exactly where to place the multimeter probes, so I can perform the troubleshooting you mentioned and see if I read +12V.

You mentioned “Place the positive lead of the multimeter on the always hot side, feeding the relay and the negative lead on the circuit board side of the relay.”

Based on that, I would place my positive lead on the thick red wire at the relay plug. This wire is +12V constant. I’m not sure where to place the negative lead though. You mentioned to put it on the circuit board side of the relay, but where exactly? Do I open up the relay to expose the internals and then place it where?
 

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I’m trying to understand exactly where to place the multimeter probes, so I can perform the troubleshooting you mentioned and see if I read +12V.

You mentioned “Place the positive lead of the multimeter on the always hot side, feeding the relay and the negative lead on the circuit board side of the relay.”

Based on that, I would place my positive lead on the thick red wire at the relay plug. This wire is +12V constant. I’m not sure where to place the negative lead though. You mentioned to put it on the circuit board side of the relay, but where exactly? Do I open up the relay to expose the internals and then place it where?

This is a bit tricky to explain without a schematic of the circuit you want to test.

Let's try this approach.

On the schematic in post #29, you will see 2 rad fan relays. One is called rad fan low relay and one side of the relay coil is tied to 12VDC. The other side is tied to a pcb (BCM I believe).

The BCM actuates the relay by pulling the terminal to ground.


This is an enlarged version of the schematic from post #29. The coil of both relays are terminals 85 & 86. With the low relay, 85 is tied to 12VDC and 86 is pulled to ground, therefore those are the 2 points to connect your meter.

It appears that the other relay (marked as by hood) is the opposite, terminal 86 is connected to 12VDC and 85 is pulled to ground. The pencil marked 14V is with respect to chassis ground. Your meter leads should be connected to 85 & 86 and you will see 12VDC when 85 is pulled to ground.


rad fan relay.jpg



Relays are funny things to measure with a multimeter. A multimeter on VDC measures a differential voltage or difference between 2 points.

To measure that relay while actuated (enabled) you require to connect the multimeter across the coil to see the 12 or 14 volts.

Relay terminal 85 is tied to 12VDC and terminal 86 is pulled to ground by the pcb connection. That's where you need the meter leads or if there are wires or connectors connected to those 2 terminals. I'd guess you may require to expose the relay terminals, at least on the schematic we're referencing.

Because of the nature of coils, if you were to measure the two sides of the coil with reference to chassis ground, you would likely see 12VDC on both terminals.

As to exactly where to place your leads, you may have to expose the relay terminals if there isn't any wiring or connectors between the relay and PCB.

Do you understand the difference between measuring the voltage across the relay coil versus measuring the relay contacts with respect to (wrt) chassis ground?



If you have already bypassed the relay (connecting terminals 30 to 87) and the fan works, it sounds like your relay is toast, provided you also measure 12VDC across the relay coil. The relay should be easy to find online or from most auto parts stores.

I was half asleep when I typed this last night. Feel free to ask any follow-up questions. :cool:


.
 
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dannyloski

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Thank you! Your explanation was very thorough and helped me understand a lot.

It appears that the other relay (marked as by hood) is the opposite, terminal 86 is connected to 12VDC and 85 is pulled to ground. The pencil marked 14V is with respect to chassis ground. Your meter leads should be connected to 85 & 86 and you will see 12VDC when 85 is pulled to ground.

With this explanation, I think I found what the issue is. If I put my multimeter’s positive lead on terminal 86 and the negative lead on terminal 85, then turn on my AC, I don’t read +12V like I should. However, if I manually feed ground to terminal 85 (brown/light blue wire), then the relay clicks, the electric fan turns on, and I immediately see +12V across the relay coil.

If I understand correctly, this means the relay is good. The issue is the signal from the BCM that grounds terminal 85 is not happening when engaging the A/C. I might have to pull my BCM and inspect it.

Given this information, do you agree with this conclusion?
 

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Thank you! Your explanation was very thorough and helped me understand a lot.



With this explanation, I think I found what the issue is. If I put my multimeter’s positive lead on terminal 86 and the negative lead on terminal 85, then turn on my AC, I don’t read +12V like I should. However, if I manually feed ground to terminal 85 (brown/light blue wire), then the relay clicks, the electric fan turns on, and I immediately see +12V across the relay coil.

If I understand correctly, this means the relay is good. The issue is the signal from the BCM that grounds terminal 85 is not happening when engaging the A/C. I might have to pull my BCM and inspect it.

Given this information, do you agree with this conclusion?

Perfect, you are on the right path and yes, the relay does sound like it functions correctly.

You're most welcome and I'm glad you found it helpful.

Because I haven't seen the schematic from your vehicle, not that they always provide sufficient info, we can't determine if there is a wire or connector between terminal 85 and the PCB which is supposed to be providing the ground.

I would be making a best effort to trace the path between terminal 85 and the PCB and hopefully, you will find an open circuit that can be restored.

Keep in mind that PCB traces occasionally get damaged and make for an open circuit. You can use your meter on the ohms scale to trace the terminal 85 ground path.

And should you find a damaged or open PCB trace, they're often pretty easy to fix with basic soldering skills. :cool:


Updated;

I should have asked if you're familiar with using the ohm meter feature. Please ask if you require any pointers, they're an invaluable tool and very quick and easy to learn.


.
 
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