Keeps blowing the M28 fuse

Tiny
SONJACAPES
  • MEMBER
  • 2011 DODGE VAN
  • 3.6L
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
I have the van listed above. Every time I start the vehicle it runs for a few seconds and then blows the m28 fuse. I took it to the dealership and they found the blown fuse after checking the battery and ground and chasing wires. They were able to start and drive it around then I went and picked it up and drove it 30 minutes home. Shortly, 10 minutes after being home I went to drive it again and it shut off. Blown m28. Now I can't start it for more than a few seconds before it blows. It doesn't throw a code because there apparently isn't one until the fuse blows. I did have the master cylinder go out on it about 2 months ago. While looking around I am noticing a lot of brake fluid that must have leaked out when that happened, could that have harmed something? I am also noticing a lot of wetness where the PCV hose comes out of the top of the intake on the right hand side. Even though it's not throwing a code for a faulty PCV valve it seems too wet to running correctly. Maybe I just don't know enough about that system it was one of the only other things that looked "off" under the hood. I looked everywhere for a rubbed wire but nothing.
Friday, February 26th, 2021 AT 8:29 PM

5 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This is caused by a couple of things but basically each of them is due to high current going through this fuse. So it could be a shorted wire or a shorted component on this fuse.

However, I have seen this before and the alternator field control is shorted/damage and it basically puts too high of current out for too long and it blows this fuse so it doesn't damage the PCM.

If it were me, I would disconnect the alternator plug and then start and run the engine. It should run for a while on just the battery but clearly you are just trying to get it to run longer then it does with the alternator plugged in to confirm this is the issue. Then replace the alternator and it should take care of it.

I attached the info below for all this. Let me know what questions you have. Thanks
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Sunday, February 28th, 2021 AT 1:29 PM
Tiny
SONJACAPES
  • MEMBER
  • 3 POSTS
Thank you. I will check this out and see if she runs. I've already replaced the alternator in this darn thing twice. A total pain, but if it works I will be so pleased to know the source of all this! Thanks again, will update.
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Monday, March 1st, 2021 AT 12:19 AM
Tiny
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  • MECHANIC
  • 18,907 POSTS
Okay. That is good info. Yeah, let's try it and go from there. We will have to dig into the power distribution if this doesn't work but it would make the most sense. Thanks
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Monday, March 1st, 2021 AT 4:17 PM
Tiny
SONJACAPES
  • MEMBER
  • 3 POSTS
Okay, I disengaged the field plug and it ran great for a good 20 minutes before I shut it off. I have dug everything up and out of the way so I can finally remove the alternator this afternoon so I can swap for a new one! I will update when complete with reinstallation.
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Saturday, March 6th, 2021 AT 12:55 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Sounds great. Thanks for the update. Let us know how you make out. Thanks again.
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Saturday, March 6th, 2021 AT 7:14 PM

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