Accessory 30 supply line going to zero under load Topic is solved

yanga001 · Post by **yanga001** » 25 Jun 2022, 22:08

Hi Everyone,

Been stumped on this one, i wired up a inverter and shorted out the 30 supply line during installation (should have pulled the 30 amp fuse). The fuse popped and i swapped it out, however the line is not holding at 12V when loaded. I have tested the overload J relays and they all test good. The inverter tested good, and the J relay i used to switch it with the ignition key (brown orange) works. I do not think i smoked out any wires and no further fuses are tripping.

From my examination of the diagram there should be nothing pulling the load down and fuse 11C/16 was changed after it popped.

: volvostuff2.png (248.77 KiB) Viewed 738 times

Looking forward to hearing back on this.

All voltages test well with no load, when loaded it goes to zero. I dont see any relays that could do that at the moment and my J relays appear to test well.

yanga001 · Post by **yanga001** » 25 Jun 2022, 22:17

Measured current on the J relay going to the 30 supply connector. It spikes to 1 Amp on first connection then goes to 0.2. What is odd is that it followed the initial connection earlier which would turn the green light on the inverter then the light would go out. It looks like a relay or something is failing open however i cant find where it would be. An electrical short would not result in a current drop as far as i know, it looks like some sort of protection is activating.

Post by **abscate** » 26 Jun 2022, 02:43

How about 11A/7 upstream?

yanga001 · Post by **yanga001** » 26 Jun 2022, 08:16

abscate wrote: ↑26 Jun 2022, 02:43 How about 11A/7 upstream?

I swapped the headlight relay with the other j relay position in 107 with no change.

yanga001 · Post by **yanga001** » 26 Jun 2022, 09:25

6 ohm connection between the relay and the 30 supply. Time to chase bad connections

yanga001 · Post by **yanga001** » 26 Jun 2022, 09:35

SOLVED: Loose fuse 11C/16 ie the accessory fuse. Resistance test indicated a high resistance connection. Sanded contacts and added dielectric grease and voila it works.

I guess an oxide layer formed as the fuse was sitting in the panel holder for a great amount of time...

Post by **scot850** » 26 Jun 2022, 10:18

It is always annoying when it is the simplest of things which we don't always check first. That is my modus operandi for electrical work!

The important thing is you found it! Well done!

Neil.

850oldschool · Post by **850oldschool** » 26 Jun 2022, 13:12

Cowl drains clear?