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There is some serious current flowing from that battery. I looked at the 3 fuses, and one is 100A, another is 125A, and the third is 250A. There is also another larger lead going back to a smaller fuse / relay panel used for the PTC heaters (pre-heaters in the HVAC ducts). I did check to be sure that the nuts were tight on all three fuse connections. Also noticed that 2 of the 3 black caps were missing. I suspect they blew off or something.
 

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Discussion Starter #23
I am going to see if I can find one ot those guys and toss it into my emergency box, just in case.....
Let us know when you figure out where to get it and cost. I spent a few minutes Googling around and could not find them. I guess you just have to go to the dealer, point to it, and say 'one of these, please'.
 

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Sorry to revive an old post, but I'm having the same problem from what I can tell. Had an issue on my 2015 ED w/62k yesterday while sitting at a series of lights in a busy area of the city. Overheated and had to pull off the road as I couldn't do more than 10mph. Popped the hood, noticed the fan wasn't kicked in like it usually is. Killed the engine to cool off a bit. Waited 5 minutes then was able to start up and get up to speed again so that I had enough air flow across the radiator. Temps went back to normal and I was good as long as I didn't sit idle for long.

Checked here today hoping someone might have had this same issue. As I read through the previous threads, I thought for sure it was just a bad (big a$$) fuse. Pulled the fuse, checked for continuity, all is good on the voltmeter since you can't see any physical signs that these types of fuses are bad just by looking at them. Still can't get the radiator fan to kick in though. I've also already checked the fuse box and have the same fuse setup that dub has. All fuses look to be good and intact. Can anyone else suggest any further testing I might be able to do? I see that there is a connector just before the rad fan. Maybe put a voltmeter on it to see if it gets current at some point? Does anyone know for sure at what temp the rad fan is supposed to kick on?

Photo Dec 19, 10 35 02 AM.jpg

Appreciate any suggestions provided.
 

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Those are Zcase fuses. 125 amp I believe goes to Power Steering. Not sure on the other two. The 250 amp power distribution. Unsure tho. U need to get with the vets here like Vern or Capn or Mas. They know more on those fuses. Unsure if any of those have anything to do with rad fan.
 

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I always like it when old threads are revived , but that photobucket new system is robbing us of
the much needed pictures sometimes.
..
onit , was the bolt loose on that positive post fuse ??
 

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Sorry to revive an old post, but I'm having the same problem from what I can tell. Had an issue on my 2015 ED w/62k yesterday while sitting at a series of lights in a busy area of the city. Overheated and had to pull off the road as I couldn't do more than 10mph. Popped the hood, noticed the fan wasn't kicked in like it usually is. Killed the engine to cool off a bit. Waited 5 minutes then was able to start up and get up to speed again so that I had enough air flow across the radiator. Temps went back to normal and I was good as long as I didn't sit idle for long.

Checked here today hoping someone might have had this same issue. As I read through the previous threads, I thought for sure it was just a bad (big a$$) fuse. Pulled the fuse, checked for continuity, all is good on the voltmeter since you can't see any physical signs that these types of fuses are bad just by looking at them. Still can't get the radiator fan to kick in though. I've also already checked the fuse box and have the same fuse setup that dub has. All fuses look to be good and intact. Can anyone else suggest any further testing I might be able to do? I see that there is a connector just before the rad fan. Maybe put a voltmeter on it to see if it gets current at some point? Does anyone know for sure at what temp the rad fan is supposed to kick on?

View attachment 58922

Appreciate any suggestions provided.
If the fuses are in fact good, then check the fan connection plug with a volt meter, if you have power there, the fan motor might be kaka.
 

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Discussion Starter #28
THANK. YOU. EvoEco!

Pictured below are the fuses mounted on the positive battery post. I wasn't sure which one it was, so I just guessed by following them into their respective wiring harnesses. One connects to a much larger loom that heads back towards the firewall. It looked like one went directly into the fuse box and the third (circled) went under the fuse box then I lost it. I decided to go for that one first.




As soon as I put my fingers on the rubber cap covering the nut, I knew I had found the problem. It was so loose that it had unthreaded itself half way up the bolt. I took the fuse off anyway. These fuses are new to me; you can't tell if they are good or not just by looking at them. Or perhaps it becomes obvious when the blow? Anyway, the one controlling the rad fan is pictured below. I snugged the nut back up, started the motor, turned on the A/C and watched the fan spin up.



I went camping last weekend which included 26 miles of unimproved roadway to get to the site; I suspect that nut rattled loose. I wonder what else rattled loose... I'm relieved I can cancel my appointment to see the dealer tomorrow. I wonder how much time they would have wasted hooking up their diagnostic equipment to look for faults and running diagnostic checks before finding that loose nut.
I re-hosted the pics from post #17.
 

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I always like it when old threads are revived , but that photobucket new system is robbing us of
the much needed pictures sometimes.
..
onit , was the bolt loose on that positive post fuse ??
Hey Kaz.....bolt was snug and tight. Not loose or blown like I was hoping for......(is it sad that I was hoping for something to be broken?.....lol)
I noticed the photobucket pictures were down, so I thought I would throw up another one for reference.

Been a couple more days.....no problems as long as i don't sit idle for long. Still haven't figured out a way to get that fan running yet.....still looking.....trying to avoid the dreaded dealership visit!

Found this thread initially with a similar issue

I don't see any info though on the relay they were referencing. Can anyone clue me in a bit more at least just to check?
 

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Turn on the a/c and see if the fan starts.
Hey D,
Sorry for the delayed response.....no change if A/C is on or off. Fan doesn't move. Can anyone tell me where to find wiring schematics that leads to the rad fan? The next step I can think of would be to start and the motor and test back to the source, but wondering how much of a pain that might be.
 

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I had overheating issues today while plowing. Like they mentioned earlier no fuses in the fuse box for the fan so I called the dealer and they were less than helpful. So I traced the fan wire to the z case fuse and bypassed it and the fan instantly came on. Called the dealer back to see about getting a replacement and they didnt know about the z case fuse on the battery post. I know you said you tested it but I would try bypassing the z case like I did when you get up to temp and see what happens.
 

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Yetti,
Thanks for the suggestion. Took your advise and yanked the fuse. Bypassed it, but no fan still. Took it a step further and stuck a meter on the grey round connector that connects the fan motor to the battery. With ignition off I have 12v, and 14v with engine running. Seems like I'm getting power to the connector. Put the fuse back in place at the terminal and still getting the same power. I'm starting to think my fan motor really has gone bad.

Can anyone else chime in with anything further I can test with a meter? Can anyone tell me what kicks the fan motor on? I've also gone through my entire fuse bank and pulled each fuse one by one to verify all are good.

Additionally, A/C doesn't blow cold when sitting at a stop, but when under way it works just fine. Temps are fine unless towing a heavy load or sitting too long in traffic. Don't mind ordering up a new fan motor, just wondering if anyone else know of anything I can test further to verify the motor is definitely toast. TIA
 

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Can you disconnect the harness to the fan and supply your own 12v and ground to the connector? I use a jump pack designed for jump starting vehicles, or a battery charger.

Shut the truck off in the middle of a regen and the fan should run.
 

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The fan speed is most likely controlled via PWM. If you have a multimeter that reads Duty Cycle(if it reads frequency it may), you may be able to read the PWM signal.
More than likely a service tech would use WiTech to force a fan speed and verify the signal that way.
 

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Bounty, just had a similar suggestion from another member here as well. Put 12v to it with ground and get nothing. My only concern is that I see a little white wire as part of the connector........

Crash..... might this be the pwm part of it? Any way to bypass it and verify the fan isn’t working?


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Yep...... I yanked the fan....... quite easy!
 

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The white wire would be the PWM signal. Check between that and the ground in the plug. Try DC volts, you may only see one or two volts if your meter doesn't read duty cycle (or Hertz).
Just out of curiosity, have you priced a replacement fan motor?
 

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The white wire would be the PWM signal. Check between that and the ground in the plug. Try DC volts, you may only see one or two volts if your meter doesn't read duty cycle (or Hertz).
Just out of curiosity, have you priced a replacement fan motor?
I’ve not yet priced a replacement. Haven’t started looking yet. If it’s $100 or so I won’t waste my time troubleshooting, it makes more sense for me just to replace considering how much I drive.

Just don’t want to get a new fan and plug it in only to find it also doesn’t turn on because of some other issue.

Crash...... am I just looking for minor voltage on that pwm? If I get the voltage what does that mean? What does it mean if I don’t get voltage.......what the hell does pwm even mean? Lol


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Just don’t want to get a new fan and plug it in only to find it also doesn’t turn on because of some other issue.

Crash...... am I just looking for minor voltage on that pwm? If I get the voltage what does that mean? What does it mean if I don’t get voltage.......what the hell does pwm even mean? Lol
PWM = Pulse Width Modulation
It's not a varying voltage or current, but an analog "signal" via digital means. It basically an On/Off output that the signal "level" is basically Duty Cycle (amount of On time vs Off time). The PCM probably uses 5V to drive this PWM signal.
It may be hard to read that white wire output as it may use a triac to drive the output, without the correct load you can get some weird readings.

Like you said, if the motor isn't too expensive, and I could see volt or two on that white wire(using a DC voltage meter), I myself would take the gamble and replace the motor. It wouldn't be the first time I've taken a similar gamble.
I have meters that read duty cycle, if you could get your hands on one, it may help with the "odds" of the gamble.
With the truck idling and the Air Condition on, the fan should being "commanded" to run at a slow speed
 
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