How the heck do the trailer relays work? (Schematic question)

[The Colonel]

Can anyone post a link to where the relays that will work with the OEM plugs might be found??

Any bosch-style 5 pin relay will work.

http://www.allelectronics.com/make-a...E-RELAY/1.html

[Strode]

FWIW Dept

I just had my trailer relay box on my '82 apart this weekend, and went thru all the relays. Mine were factory original Bosch relays.

IROC, you're a whiz for being able to lock at the schematic and figuring out it wouldn't work as drawn. The 'corrected' drawing by Rollie715 in post #6 is correct, and the original schematic is wrong, as the Colonel verified.....

With one exception:

On the 4th relay marked as 'backup lights' (which is really taillights), the RED WHTR wire goes to the 87 post of the relay, and the WHT goes to the 30 post of the relay. In the same way that the other 3 relays above it have those 30 and 87 posts flip-flopped.

If I could manipulate drawings on the computer I would redraw it again.

Blake, that Bosch guide is really helpful. I tested all my relays with a 9v and an ohmmeter. When I put mine back together, I also ran an extra relay ground from inside mine that I will ground to the frame, instead of relying on the box being a good ground to the frame.

[Walt]

Any bosch-style 5 pin relay will work.

http://www.allelectronics.com/make-a...E-RELAY/1.html

But not all Bosch style 5 pins are the same! I got a couple at the auto parts store a while back (didn't scrutinize the relay's diagram) and wound up with single pole relays. They had all of the terminals, but differed inside and the little diagram on the relay housing should have clued me in.
That caused several hours of enjoyment before I figured out the deal...

[iroc86]

Great observation, Brad. The naming of the fourth relay was an error on my part. I probably ignored the wiring of this relay because the orientation of the 30 and 87 pins don't affect its operation, but it's still good to have the right information.

I've updated the schematic for you guys.

[Strode]

Nice work on the drawing.

This should be a sticky in the tech archives.

[jpcoutts]

Great work on the diagram. Does anyone know if it applies to Jtrucks?

[Strode]

Just to update this thread, and I have moved it to the electrical archives.

My 82 Cherokee came with the trailer towing package, and a 7 pin factory trailer plug.

As far as I can tell, when you have the trailer package with the little black box of 4 relays, there is no way to just add a 4-pin flat connector. The lights will work, the turn signals will work, but brake lights on the trailer won't light.

You need to either go thru the factory 7 pin plug using a flat 4-pin adaptor, or you have to add relays like Tony mentioned. I went thru my box and made sure all the relays worked, and used an adaptor.

You must have the 12 gauge bullet connectors, one in and one out, hooked to a hot source. Otherwise, you will hear the relays working, but nothing will come out of the 7 pin plug?. (that was my trouble)

[Strode]

Great work on the diagram. Does anyone know if it applies to Jtrucks?

I read where somebody posted that the J-trucks were different. I have no source on that.