Dual Battery setup Prado - Jayco Hawk advice

Gday, Was hoping to get some feedback into the way I wired up the dual battery system & tekonsha brake controller etc into my Prado 150 & Jayco Hawk camer trailer. I did it all a few months back & all seems to work ok, however something seems to be not right with the electric brakes to the camper trailer. When I had a similar setup in my previous vechile (Kluger) the camper trailer brakes would lockup with ease, with the Prado setup I cant get them to lock even though I've replaced brake magnets / machined drums & installed heavier gauged wire. The current seems good & I'm pretty sure it's on the prado side of the wiring.

I've just put together this diagram as to how I've wired it up & would apreciate if anyone can see anything that may attribute to this or have a suggestion ?

Cheers Don

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Reply By: ss--ss - Friday, Jan 27, 2012 at 19:59

Friday, Jan 27, 2012 at 19:59
Oops , Original is a bit hard to see , hopefully this is better

AnswerID: 476132

Reply By: Member - Fred B (NT) - Friday, Jan 27, 2012 at 20:29

Friday, Jan 27, 2012 at 20:29
I can see a number of issues right off... However I will deal with the brake controller only.
I do not believe you should have the UHF connected to the same supply as the brake controller. Also you should have a much smaller fuse for the radio to protect it. Brake controllers can be funny things and be upset by some of the smallest things.

The brake controller should be mounted correctly at the correct angles otherwise they just do not work effectively. Have you mounted it according to instructions?

Hope this helps.
Fred B
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AnswerID: 476133

Follow Up By: ss--ss - Friday, Jan 27, 2012 at 20:44

Friday, Jan 27, 2012 at 20:44
Thanks, I'll move the UHF radio off the circuit breaker to see if that improves things..
The UHf radio has another fuse which I didn't include in the diagram but is right behind the radio to protect it at the correct rating & the brake controller is a P3 & is mounted at the correct angle.

This Don
FollowupID: 751158

Reply By: Member - Captain (WA) - Saturday, Jan 28, 2012 at 04:34

Saturday, Jan 28, 2012 at 04:34
Hi Don,

Assuming nothing has changed on the camper, then the Prado is the obvious starting point. You show the +ve wiring for the brakes, but not the negative. How is the camper getting its -ve power?

The gauge of wire for the negative needs to be the same as the +ve, as they will both need to carry the same amount of current. Often the vehicle wiring will simply have the -ve wire earthed to a chassis screwed at the rear. I would suspect this connection is poor and may be the cause. Try ensuring a good earth is made and see if it makes a difference.

Also, I have seen issues with the plug connection itself. While all may appear OK, the pins can lose tension and not be a tight fit into the socket.

As for the UHF, as long as its on a seperate fuse, then there is no problem running it off the same cable. Your original diagram appeard to only have a 25A fuse and this is too large for a typical UHF radio.


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AnswerID: 476162

Follow Up By: Member - Frank P (NSW) - Saturday, Jan 28, 2012 at 10:51

Saturday, Jan 28, 2012 at 10:51
It seems to me the negative circuit is provided by the Anderson. I suggest checking all the earth connections in both the Prado and the caravan.

Maybe try a temporary Aux neg to main neg jumper lead to bypass the chassis earth between the two batteries - that will give a direct WIRED negative all the way through to the controller. If that fixes it, you have a clue as to where the problem lies.

Also, consider completing the negative through the trailer connector - I have known more than one Anderson to disconnect while driving. Though uncommon, if it were to happen to Don he'd have no negative return in his current setup, and therefore no van brakes, even though he has a positive supply via the trailer connector. I would wire it from the matching pin on the Prado connector direct to the neg on the main battery, to supplement the chassis earth. Overkill, I know, but you minimise the chances of a chassis earth connection going bad and robbing you of brakes.



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Follow Up By: ss--ss - Saturday, Jan 28, 2012 at 13:49

Saturday, Jan 28, 2012 at 13:49
G'day & thanks for the info..
I've been out tring a few things this morning & it's now locking up when I put the tekonsha up to 9volts & use the manual override. I found that the neg wire to the magnets had been half cut through on the jayco, either by a rock on a dirt road or touching the leaf spring..I've sorted it out so think that was it !

Also FYI , the UHF radio also has a low amp fuse behind it which came with it from gme but I missed it on the diagram..Also I didn't include the standard trailer plug wires like lights & ground..

The point about Anderson connectors not connecting actually happened to me once.. I drove from syd to nyngan expecting the battery to be charged up only to find corrosion on the 175amp pins creating open circuit.. Bit of sand paper & it was all good for the next 10000klm.

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