WTH: ARB 24v compressor control harness is dangerous. (easy fix however)

Joined
Aug 5, 2019
Messages
161
Location
Colorado
OK, so I ended up with an ARB 24v dual compressor. It's a nice piece. I'm going to run it off my 24v lithium pack.

But... I am not impressed with the control harness. It's a bad hack to make a 12v harness and fan system work in a 24v system.

The harness includes wiring for three switches (compressor, 2x lockers) which is nice.
However, the harness is built to use 12 volt power to control the 24v system.
In the case of the built in relays on the compressor stack, it's not good.

ARB decided to include a small "ground" lead that you're to hook up to the - terminal of the upper 12v battery.
What's bad here is that this line is treated as a ground, but it's +12v, hot through the entire harness.
It feeds up to the switches and is used to provide ground signal to the relays and fan, providing the effective 12v.

This isn't the end of the world, but this lead should absolutely be fused if you're running it this way. Without a fuse, it's dangerous.
Add a 3-5 amp fuse inline, and you'll be back to the land of safely wired gear.
 
Joined
Jan 11, 2019
Messages
85
Location
Sacramento
I don’t have that harness but if you have two 12V batteries in series they could be using that “ground wire” as a reference. Putting a fuse on that is the same as putting a fuse on the + leg. DC systems don’t have grounds per say.
 
Joined
Aug 5, 2019
Messages
161
Location
Colorado
I don’t have that harness but if you have two 12V batteries in series they could be using that “ground wire” as a reference. Putting a fuse on that is the same as putting a fuse on the + leg. DC systems don’t have grounds per say.
They are using it in order to use 12v switching hardware (and a 12v cooling fan) on a 24v system. So, all of the 'negative' wires in that harness are at 12v all the time with no fuse. That said I'm going to isolate the thing on my rig.
 
Joined
Aug 5, 2019
Messages
161
Location
Colorado
Almost forget this as well - given the same approximate load as the 12v version, the 24v version is likely over fused since both use the same 40a fuse harness. In reality the 24v should probably have 25a or so, but I haven't measured load yet.
 
Joined
Jan 11, 2019
Messages
85
Location
Sacramento
The “negative” wire actually would have 0V (it’s counter intuitive) . It’s all about what’s being referenced. Looks like they are using for references on the switches because they are rated for 12V(that would be my guess). Either way it can’t hurt to put a fuse on it, the diagram for ARB harness I found has one it (might be a different compressor).
BCCE896B-4FD6-498D-8DE3-30A80CA8307E.jpeg
 
Joined
Aug 5, 2019
Messages
161
Location
Colorado
The “negative” wire actually would have 0V (it’s counter intuitive) . It’s all about what’s being referenced. Looks like they are using for references on the switches because they are rated for 12V(that would be my guess). Either way it can’t hurt to put a fuse on it, the diagram for ARB harness I found has one it (might be a different compressor).
While that's correct from the harness switching perspective, I'm talking about relative to the chassis, where it has +12v, making it a hot wire. Having a wire wear through against the chassis is my concern here - and it would get hot and cook off if it did.
 
Top Bottom