2013 386 peterbilt relay clicking

[JimT]

it's a rare occurrence when someone comes on here before being the victim of a bad delete AND actually learns to avoid this all too common problem.

I have a 2012 587 with a cm2250. been down the road you're on in my own way. I confess I didn't read all of rawze's posts above so apologies if I repeat something he said above.

As for your DPF/Regen issues you're basically looking at 1 of 3 potential causes.
1) the entire aftertreatment system has been severely neglected and will need extensive TLC in the form of an EGR tuneup. (Including dpf injector) Also seek out and fix any exhaust leaks as this will mess up what the sensors think is going on in the exhaust.
2) The DOC/DPF are past their life expectancy and need to be replaced. (or remedied. Hollow cans really aren't noticeably louder then stock ;)
3) The inframe/rebuild was poor quality or cut corners by not doing everything that should be done and the engine is running so bad it's overwhelming the aftertreatment systems. OR there's something wrong, not related to the rebuild, that has the same effect.

It's really as simple as that. No matter which road you go down, fix/replace aftertreatment or demandate, you will most likely still have something on the engine that needs fixing before you're done.

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As to your original question, a possible relay, I don't have any definitive answers. But maybe some generic advice might help. One good thing about these trucks is that it's really easy to get into the dash and poke around. That would be my first suggestion. Could have a stripped wire making occasional contact, could be a hidden relay, could just be some debris (or wiring or fixture) rattling around in there. Open her up and see what there is to find. snap some pics and post em if you have any questions. Also might want to open the hood and inspect the wiper area just under the widshield. If you're truck style is similar to mine then there's plenty of space up there for stuff to get stuck and rattle around. Given the location it'd be easy to think the sound was coming from inside the dash instead. Same goes for the upper rear section of the engine bay.

Does the sound correspond with anything else happening at the same time? Such as maybe the air compressor kicking on/off?

Also, what is the mileage currently on the truck?