Cougar 5th wheel blowing 120v fuses

[spookylake]

When only using onboard battery - voltage on Fridge and A/C fuse is 12vdc

When using both battery and shore plug - voltage on Fridge and A/C fuses goes to 24vdc (blows the 40amp fuses)

When using shore plug only and battery disconnected - fuse is fine and everything works fine.....except none of the 12vdc items work like awning, slide etc.

any assistance greatly appreciated

[JRTJH]

If the 40 amp fuses you say are blowing are the "reverse polarity fuses" on the converter, they will only blow if the battery is connected backwards. The black wire is POS and the white wire is NEG. It's easy to confuse trailer wiring (black wire=POS) with truck wiring (black wire =NEG).

Double check your battery connections and replace the "reverse polarity fuses" and hopefully you'll be back in business.

[chuckster57]

Are you using 2 batteries? Are they 6 Volt or 12 Volt batteries.

If two 12V batteries the positives need to be connected to each other, and the negatives together.

24VDC sounds like two 12V batteries hooked up in series not parallel.

[spookylake]

JRTJH....

you were absolutely correct, he had the battery installed backwards.
swapped the pos for the negative and it works perfect.

thank you very much for all the help