Trailers and controllers and wirings and stuffs... (1 Viewer)

[Sundowner]

So, it's something in the ground circuit of the relay block, I think. Energize any circuit - running lights, turn signals or brake - and the fuse pops...but only when the relay block is connected. The trailer harness that inputs to it is working fine...but once those relays are connected, things start shorting. I've checked the wiring diagram, continuity and the voltage across various points, and everything seems correct. I have good 24V grounds on terminal 86, my 24V inputs are correct on 85, 12V+ is correct, etc, etc. I'm lost.

 

[Sundowner]

Tried swapping the 85 and 86 terminals on the running light relay, so the 24V ground and input were reversed from the original diagram but correct positionally; still blew the fuse. I know I'm missing something simple.

Edit: tried swapping 87 and 87a just for the hell of it...and it still pops the fuse as soon as the circuit is energized. I pulled the 24V chassis ground, and that kills everything...as expected. So it's something to do with how the 24V input signal is being handled by the relays...and I have no idea how to fix that.

 

[Sundowner]

Looking at the diagram isn't helping me... most likely because I'm lost, as aforementioned.

Pictured: It could work...it just doesn't.

Looking at the diagram, what I'm getting on my meter sort of makes sense. 85 has continuity with 86, and 30 is contacting 87...so that means that the input signal from any given 24V light (terminal 85) is running to ground (86), which is what's on the original diagram. 30 is default connected to 87a, and should either switch to 87 or go nowhere when the 85/86 circuit is energized...which is what's on the diagram.

 

[AirheadNut]

Are your fuses for the switched power, or the relay power? If the fuse that is blowing is for the switched power, then the ground circuit for the relay block won't have any effect on it. If the fuse is for the relay power, then either one of the relays is hooked up wrong or you have a failed relay (unlikely, but possible. They normally fail open circuit rather than closed circuit).

If swapping 87 and 87a still blew the fuse then your problem is not with the relay, it is somewhere else in the wiring. Somewhere you've got a positive wire that is grounding out.

Convention for relays like the one pictured is as follows:
85: + trigger signal
86: - trigger ground
30: + switched power in
87: normally open (no continuity with 30 until relay is energized)
87a: normally closed (continuity with 30 only when relay is not energized)

On that particular relay, and in general, there is a diode between 85 and 86, preventing operation if the power to the relay is hooked up backwards (negative to 85 and positive to 86).

 

[Sundowner]

Airhead, I think you're on the money; the 85/86 diode issue may be at fault...along with my titanic levels of ignorance.

The original diagram - linked on page 1 - doesn't acknowledge the non-reversibility of the diode relay (which I didn't even know about until approximately the same time that your were posting) and I think that's because the original Hella relays didn't have diodes. I went by that diagram for my 24V Bosch units, and I'm pretty sure that not only have I fried all four of them, but that they failed closed.

I grabbed a non-diode surplus 12V relay from the alarm system demolition, and I did not get the same continuity tone across 85 and 86 that I'm getting on my Bosch units; instead, there's just a light static buzz. I'm guessing that I'm getting that from the coil...but I don't have any more 24V relays to test, so this is just a theory. However, it's one that's somewhat proven by a late-game adjustment that I made:

In accordance with The Great Charter of Diodes, I reversed the 85 and 86 wiring, and now I have ground to 85 and input to 86, and I slapped the surplus 12V relay in place just to see what would happen; I figured it would die quickly or blow the 24V fuse for whatever was actuating it (like the previous eight attempts) but that's not what happened. I tried it on the running light circuit and energized it...and no chassis fuses blew. Instead, I got a *click* from the relay.

Hmmm...

Tried it in the turn signal position: click, click, click, click...

I'm certainly not an expert - if I was, this wouldn't be happening - but that seems to say that as I tried circuits previously and saw no activity except blown fuses, the relays were failing closed and taking the fuses with them. Thus, nothing I did afterwards was changing that...but after the aforementioned adjustments, there's less immediate electrical failure.

So, my current problem is that there are no 24V relays available locally...at least not that I can find. I reordered the ones I've destroyed, but they won't be here until Saturday...so I'm going to do a bit of re-wiring tomorrow, hopefully get all of this cleaned up and looking better than it currently does, and see where I get.

On another note: the 73 doesn't have a name. I keep trying to find one that fits, and nothing ever seems correct...but I'm starting to think that "Eleanor" might be slightly more appropriate than I'd like to admit.

 

[jblueridge]

Not very helpful at this stage but I buy from Digikey quite often as they have an amazing selection and sensible filters that let me find exactly what I need.
digikey

 

[Sundowner]

So... found an assortment of relays here and there. Bought several, and hopefully they'll be here tomorrow. Having now had to wire/unwire things in and around the block, I think I'm going to make a couple of small changes that'll let me work with it much easier than I'm working, now. First on the agenda will be getting rid of the heat shrink and rear terminal keepers; neither of those things is working very well for me. And now that I know the wiring is roughly correct, I can actually simplify things how things are put together.

 

[Guyute]

Yikes. What a roller coaster of a project. Thanks again for posting all the detail. I'm learning a lot and stoked I'm several steps behind you. Headed out to garage to make sure my relays don't have diodes.

B

 

[Sundowner]

Yikes. What a roller coaster of a project.

It would have been easier if I knew anything at all about what I was doing.

Thanks again for posting all the detail. I'm learning a lot and stoked I'm several steps behind you. Headed out to garage to make sure my relays don't have diodes.

Wise decision...and you're welcome. When I'm finished with it, I'll try and get a cohesive list together that calls out the salient bits of info that I've discovered, and then get that inserted into the first post; that way, nobody has to scroll through all my nonsense to get to the important parts that everyone else has contributed.

 

[Sundowner]

Well, it's been an interesting couple of days...and not just because I got a $20K quote for the paint and body repairs that I'm electing to have done on the Cruiser. Note the key word, there: electing. I didn't know that outside of the world of classic Italian/German sporting vehicles, one could elect to have twenty grand of minor paint and sheetmetal repairs done that are not even remotely necessary...but evidently, that's totally a thing. But, I digress.

Having realized that I may not be able to get non-diode relays in time to actually use the results of this project - and I'm on an ever decreasing deadline that's being bolstered by a series of gratuitous extensions - I elected to swap the ground and input sides of the relay block, so that I can use either relay option; a standard relay should work with the trigger in either direction, and a diode-relay should be perfectly happy as well. However, due to the larger wire gauge that I used for that portion of the wiring, things got cramped and difficult behind the block itself...so I ended up rewiring it. Now, the 24V trigger circuits are in the same 20AWG as the taillight harness, the ground for those circuits is pulled from the same harness, and the 12V power is being run into the same connector...so I have only a single path of wires going inward. It's cleaner and neater.

Pictured: The new hotness.

It's actually very hard to tell what's going on there, but that's the intermediate taillight harness on the upper left and the 12V power wire on the upper right. They're both cable-tied to the exterior metal, and the weird arrangement allows everything to be unclipped and removed with minimal fuss; it's the best I could do with leads coming from both directions. You can see the driver's side intermediate harness a bit better.

Pictured: Not factory, but close.

It's a pretty simple arrangement on this side: four factory-ish-colored wires that pass directly through from one connector to another, and one with a Y-splice - the right turn signal - that leads off towards the passenger side. That's the braid-loomed bit...and no, it was not easy to get it from one side of the vehicle to the other without placing it anywhere in danger.

Pictured: Witchcraft may have been involved.

All other signals - and the ground - come from the passenger side; that configuration uses the least amount of wire, and has the least chance for failure. After that last pull was completed and the left taillight intermediate harness was buttoned up...well, it was actually pretty underwhelming.

Pictured: But there was much rejoicing.

It's almost impossible to get a photograph of the relay block output harness; it's buried in the lowest, sub-basement corner of the tub, and it exits from where Toyota placed a convenient rubber grommet through the sheetmetal. Best I can do is show the upper section, which actually shows the intermediate harness that I built more than anything else...

Pictured: But there's some more below this, I promise.

That other loomed wire is the ground, which is running directly from the 12V fuse block. It looks wonky in the photo, but it's actually pretty good when you look at it in perspective...and of course, it's all hidden once the trim panel goes back in.

Pictured: It's not so terrible.

I'm not displeased. And the exterior part of the harness was actually pretty easy to install and route, because Toyota already ran harness-parts underneath the body in the back...so if you just follow that from the through-panel grommet back towards the center of the vehicle, you'll get a pretty clean and simple install. I'm not sure that I got a picture of that part of things, because I was in a hurry to test everything out and make sure that my replacement relays worked...

...

...

...which is exactly what they proceeded to not do.

To be completely honest, I'm not sure what went on; I got a set of four non-diode Bosch relays, checked them for function, revelled in the gratuitous clicking that came from the block, and went on about my rewiring and everything else that I've already covered. But when I plugged in my trailer light checking dingus: nada. The running lights worked, but the brake and both turn signals were non-functional. I also bought a replacement diode relay and exactly one (1) of the correct Hella units, just to check them out. I tried swapping in the Hella and got no change at any position...but when I swapped the diode relay into the brake circuit: turn signals started working. I'm not sure what's going on with that, but I suspect that now that I've swapped the grounds and inputs, I have to use diode relays. That admittedly makes zero sense to me, but when my replacement set of diode relays showed
up - I think I'm up to about ten total relays, now - I threw them in and checked it all once more to see if i finally had any function. The result...

 

[jblueridge]

I'm glad to see it working!

 

[Guyute]

Super clean!

 

[Sundowner]

I'm glad to see it working!

You and me both.

Super clean!

It's not so terrible, but I still have some things that I'd like to change and clean up...but thank you, nonetheless.

 

[AirheadNut]

The diode in a relay isn't actually a bad thing, and if hooked up properly will be perfectly reliable. Here is some interesting info about the purpose behind putting a diode in parallel with the relay coil: Why is there a diode connected in parallel to a relay coil? - https://electronics.stackexchange.com/questions/100134/why-is-there-a-diode-connected-in-parallel-to-a-relay-coil#100139

 

[Sundowner]

Just got in from hauling a bunch of stuff yesterday; the light circuit worked flawlessly...but man, do I seriously want a turbo for going up hills with 6,000 pounds behind me...

 

[Sundowner]

Pictured: Things you can haul around with a 1HZ.

Also, there was a lathe, a punch press, a brake, a sander and about 500 pounds of random stuff. So, let's call it 6K with the trailer. Good job, old girl...good job.

 

[svsisu]

Pictured: Things you can haul around with a 1HZ.

View attachment 3357038


Also, there was a lathe, a punch press, a brake, a sander and about 500 pounds of random stuff. So, let's call it 6K with the trailer. Good job, old girl...good job.

Work horse. Nice milling machine!

 

[JDM Journeys]

Pictured: Things you can haul around with a 1HZ.

View attachment 3357038


Also, there was a lathe, a punch press, a brake, a sander and about 500 pounds of random stuff. So, let's call it 6K with the trailer. Good job, old girl...good job.

I call fake news!

I'm assuming you're at sea level with a tailwind? Some days I'm wishing I didnt have the extra weight of my dog onboard... And she hasn't cracked 20 pounds yet.

 

[Sundowner]

Work horse. Nice milling machine!

Yeah, it's a decent one, methinks. Just right for a pint-sized shop.

I call fake news!

I'm assuming you're at sea level with a tailwind?

Actually, yeah... that's about right. You can't live in costal Washington without being at sea level...and the breezes from the sound are pretty nice.

Some days I'm wishing I didnt have the extra weight of my dog onboard... And she hasn't cracked 20 pounds yet.

I think mine just passed 140-something. Three years old and still putting on weight...