Problem with Aux trip / voltage drops on PMS3H

[Masami2k7]

I’ve been trying to figure this out for a couple of years now, I’ve a T5.1 camper and my aux power on the PMS3H is intermittently dropping voltage to around 5v when it’s being used, when it happens nothing powers up anymore and normal service seems to resume about 15-20 mins later and no other 12v devices seem to be at all impacted (ie my fridge and lights). I’ve swapped out both the 12v USB adapter and the 12v outlet for newer models and this continues to happen, I am not putting heavy drain on either, just phone chargers. I have a relative new decent brand AGM battery. This issue seems to happen both on and off the 240v hookup.

 

[kipperman]

That is somewhat suggesting the the PMS3 is not working as designed. Assuming all fuses are OK, although a blown fuse unlikely to have the symptoms you are suggesting. From what I can see, and given that it is a T5 the PMS is somewhat long in the tooth, so some form of internal failure certainly possible.

I can't find any circuit diagram for it so no idea as to the likely nature of the fault. I'd be taking it apart and looking, but I'm pretty confident with electrics.

Could you at least take it out of its hole and check that the external connections are OK and not corroded (making well sure that not connected to EHU!!). Looks like a plastic connection block from the pics that I can see.

 

[Masami2k7]

Thanks, I have checked all the external connections, they are as you described and seem to look fine.