Guardian IQ Brake Controller - "No Contact" Problem

Submitted: Monday, Jan 23, 2023 at 18:56
ThreadID: 145273 Views:623 Replies:3 FollowUps:2
Three years I began using the portable brake controller harness and it worked well until recently I destroyed both 7-pin flat plug and socket at the rear end of the 5m through-cabin lead. (Left the lead hanging out the back door for 20km return trip from the bush retreat to Nitmiluk Gorge!!!) I replaced the plug and socket assembly but since then I have been getting "n.c" readout on the controller. I checked and re-checked the plug and socket wiring and all seems fine.

The troubleshooting section on the user manual sheet mentions possible open circuit in the caravan earth wiring. But the earth pin on the caravan plug shows continuity with the chassis.

The current wiring is below. The red wire from the controller picks up the stop light circuit from the vehicle at the stop light pin in the socket which joins to the caravan plug. The heavy duty blue lead from the controller links to the service brake pin in the same socket. Any suggestions about further checks would be appreciated. Now in my 80s I make lots of mistakes but I enjoy fixing them! On this one I need some assistance.



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Reply By: Gary T7 - Monday, Jan 23, 2023 at 23:42

Monday, Jan 23, 2023 at 23:42
From what I see on your schematic your power (black) earth (white) should come directly from the battery, not from your lighter socket which doesn't have enough current to supply brakes .This battery supply should have a circuit breaker in line, not a fuse as you need the circuit to make again so you have some braking. If fuse is used and it blows you will be without brakes .This should be done for safety.
A lot of lighters have a fusible link incorporated in the rear of the lighter this may be blown.
AnswerID: 642713

Follow Up By: OzzieCruiser - Tuesday, Jan 24, 2023 at 12:15

Tuesday, Jan 24, 2023 at 12:15
But it is a portable brake controller and works from the 12v socket - as the op has said has worked for 3 years so not an issue. I have the same unit and works fine as designed.

For the OP if it worked before and not now then you have made a mistake in the rewiring.
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FollowupID: 922303

Reply By: qldcamper - Tuesday, Jan 24, 2023 at 07:41

Tuesday, Jan 24, 2023 at 07:41
Time to break out the multimeter.
AnswerID: 642715

Follow Up By: Adrian W6 - Tuesday, Jan 24, 2023 at 20:34

Tuesday, Jan 24, 2023 at 20:34
Thanks Gary and Ozzie. Yes it seems yet another multimeter exercise is needed.
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FollowupID: 922306

Reply By: Kevin H16 - Friday, Jan 27, 2023 at 02:57

Friday, Jan 27, 2023 at 02:57
Breaking out the multimeter ican be the path to finding the issue. However a fast path to test your controller is to try connection to another trailer unit.

If your controller shows connection on another trailer the likely culprit is broken wiring immediately adjacent to the magnets within the brake drums.

Not always easy to hook up to another trailer so here is a plan to follow with the multimeter.

I recently experienced an issue like yours and ultimately traced the issue to broken wiring at the brake magnets. Situated within the brake drums.

I was fortunate that the brake circuits were fitted with plugs where the supplied brake wiring joined the trailer wiring so separated the plugs and the continuity through the magnets was easy to check..

Seems that wiring breaking at the magnets is not that uncommon because of c
Vibrations causing the copper wires to harden and ultimately break. Vibration of course from corrugating.

Off road magnets are different to on road versions. Off road ones have a slot to fit onto the arm that moves to apply the brake and each magnet is specific to either left or right side. On road magnets have a cross of slots such that the magnet is not side specific.

Breaking of wires on one magnet does not show up on the controller since having one complete circuit still results in a connection so far as the controller is concerned. It is only when both have failed does the lack of circuit show up on the controller..

If you need mnew magnets shop arround as prices I found can vary by over 60 %.

Good luck.
AnswerID: 642733

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