Followup on trainer wiring

Submitted: Wednesday, Jul 06, 2005 at 09:11
ThreadID: 24484 Views:2331 Replies:2 FollowUps:5
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Hi all. Posted a question on trailer wiring last week (indicators not working), and thought I'd let you know what happened. I couldn't get an answer off anyone why there might have been additional flasher cans in the trailer wiring loom indicator wires, but turns out that these things were RELAYS instead. Screw those two shop guys who originally said they were flashers. Anyway, easy now... even for me. Wasn't working cause the main circuit had no power at all, so spoke to Toyota, the previous owner (who said it was factory done) and then the original dealer who all said NFI. So I cut the relays out and wired directly. I guessing it was the service brakes wire that they were wired into, but not sure, and guess why anyone would do this originally anyway.

Now found the 2nd start & power switches not working... bugger. Might have shorted something testing the relay on the weekend, or kids might have kicked it to death climbing around the front seat at the drivein the other night. Back to fuses and poking around....
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Reply By: drivesafe - Wednesday, Jul 06, 2005 at 09:51

Wednesday, Jul 06, 2005 at 09:51
Hi Tonester, Is your vehicle fitted with a computerised fault indicator.

If so, this could be one reason for the relays.

Some of these fault finding systems can not have trailer wiring connected directly to the vehicles existing wiring without causing problems.

The device you have sounds a bit like an after market interface module.

The genuine article can be as much as $1,000 while the after market devises are only about $150. So you can see why someone might have the other type fitted and no one knows anything about it.

Just a thought.
AnswerID: 119069

Follow Up By: Member - Tonester (VIC) - Wednesday, Jul 06, 2005 at 10:24

Wednesday, Jul 06, 2005 at 10:24
Previous owner said nothing fancy was done, but I guess by now unsure how complete the truth is he's telling me. No idea about the computerised fault indicator.
FollowupID: 374220

Reply By: Member - Matt Mu (Perth-WA) - Wednesday, Jul 06, 2005 at 11:07

Wednesday, Jul 06, 2005 at 11:07
Tonester didnt someone say that they were relays when you originally posted this problem. I believe a few manufactures have additional relays in the rear quarters of theiur vehicles for the extra load when a trailer is hooked up. Some have the provisions and are only fitted if you get the factory "Tow" pack option.

If you jump in the back of a Jackaroo and hit the indicators you can hear the relays clicking away in the rear right quarter panel!!

The fact they are not working, suggests to me you have a little problem back up the loom. They would be standard relays and it should be pretty easy to determine the power suppy and switching circuit wiring to find what is not doing what it is supposed to be. ie the might have load power but the switching isnt there or vice versa. Just from personal experience you dont USUALLY get electrical problems unless something has been disturbed, either physical damage, stone or chaffing...or someone has been playing, like wiring up trailer plugs etc!

Without being able rto play with you truck a scenario might be...the relays use the sense of the actual indicators wiring and load is supplied, if someone wired up the trailer plug incorrectly and the switching circuit has interupted that supply to the relays!

Goodluck with it...finding elec probs can be a nightmare, but I find the best solution, is do the easiest first and then start off with a dedicated process of elimination. ie if you know the sense circuit is not present, look up the loom for the main body plug and test it there, then you have eliminated the problem rear of that point etc!


AnswerID: 119084

Follow Up By: Member - Tonester (VIC) - Wednesday, Jul 06, 2005 at 12:14

Wednesday, Jul 06, 2005 at 12:14
I did take it to Toyota and just showed them the wiring. They said that the 6 pin plug (6 cause earth not included) coming out of the loom behind the rear lights is standard and is pre-wired for brakes, lights, signals, etc for a trailer wiring loom. The guy had not seen relays installed before between that point and the actual trailer plug.

I could spend ages trying to reason why the relays are there, and probably at a lot of money. I just took the relays out and wired green to green, etc. Works fine.
FollowupID: 374233

Follow Up By: Member - Matt Mu (Perth-WA) - Wednesday, Jul 06, 2005 at 13:13

Wednesday, Jul 06, 2005 at 13:13
Wooah! Correct me if Im wrong but did the Toyota guy tell you the six pin trailer plug doesnt have an earth???

I think you will find he is sadly mistaken and there HAS to be an earth!!

I would check up on that if I were you, I use 7pin round and flat plugs and both have to have an earth pin, so without looking at a 6pin diagram, I cant see how they would operate without it!

FollowupID: 374239

Follow Up By: Member - Tonester (VIC) - Wednesday, Jul 06, 2005 at 13:33

Wednesday, Jul 06, 2005 at 13:33
Not quite in those words, no. Behind the lights inside the truck in the jack compartment, the main wiring loom of the truck has a 6 pin plug branching out of it. That plug is for any trailer wiring. Left, right, stop, lights, reverse and service brakes(guess). Its that white plastic plug he said was standard, towbar attached or not. From there, add on the trailer's wiring loom which comes in from below through a grommet and connects to that plug. That trailer wiring loom has an earth connection to the chasis, done inside the same jack compartment.

I think you might have thought I said that there is no earth pin in the trailer plug itself located outside the vehicle. Which there certainly is.

Lol. I hate trying to explain these things, I know not much about, its hard.
FollowupID: 374240

Follow Up By: Member - Matt Mu (Perth-WA) - Wednesday, Jul 06, 2005 at 14:42

Wednesday, Jul 06, 2005 at 14:42
Ahh yep with you now, yeah the manufacturer plugs dont have an earth, you wire directly onto the chassis when you fit the 6 or 7 pin plug to the vehicle!

FollowupID: 374251

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