520H headlights

[sttereve 30]

Recently acquired a 520H, and I'm trying to get the headlights working.

 

The good news is there is 12 volts all the way to the spade connectors, but neither light lights up. Normally I'd just assume the light is bad and get a new one BUT I tried running jumpers directly to the battery and it comes to life no problem. 

 

I'm no electrician so I am now stumped. I checked the resistance and it seemed to jump around a lot, but generally hovered around 2 ohms. Thinking maybe the light is only "mostly dead" and is only able to pull enough juice when coming right off the battery?

 

Any ideas to test?

[ri702bill 7,445]

Check that the ground wire is present, clean at the connections and undamaged....

Some models ground thru the pivot hinge (poor design) without a dedicated wire to go back to the frame...

Edited November 27, 2022 by ri702bill

[sttereve 30]

This has the dedicated wiring for ground (green and black wires).

[lynnmor 6,850]

When you check that 12 volts, put the voltmeter probes on the terminals at the lamps.  As said above, you likely lost a good ground.

[Jayzauto 89]

Jump Ground of the Lights Directly to B- to complete the circuit.   

 

I use a Power Probe for testing wiring.   Quick and EZ.   Tests for B+ as well as B-, Not to mention that it will Supply B+ and B- at the flick of a switch.  Invaluable tool for electrical testing.

 

 https://www.amazon.com/Power-Probe-III-Clamshell-Automotive/dp/B00G4YUWMC/ref=asc_df_B00G4YUWMC/?tag=hyprod-20&linkCode=df0&hvadid=309806250188&hvpos=&hvnetw=g&hvrand=11111561096923130483&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9002054&hvtargid=pla-376660908451&psc=1

 

 

Single best tool I've EVER purchased.   I now own 7 of them.  Spread out Anywhere I may do testing.

 

 

GLuck, Jay

[sttereve 30]

Ran a jumper to ground and even all the way back to the battery and still nothing. I think I'm going to pick up a new one to test with. If that still doesn't work it must be a wiring issue somewhere.

[sttereve 30]

Tried a brand new light, still no luck. Gonna try it with a jumper at the switch and see what I get. 

[sttereve 30]

Cleaned up all the connections and it's working now wooo! Thanks all!

[sttereve 30]

Well that was short lived, went to take it for a test drive today and it died after about 10 ft. Fortunately I hadn't gotten out of the barn yet.

 

Will not start, here is what I know so far:

- no 12v going to the starter solenoid on key turn

- all fuses are good

- lights and other accessories work

- based on indicator lights all safety switches are good

- engine wiring harness has 12v from battery and there is good continuity from harness to solenoid

- I suspected a bad ignition switch. After pulling and testing it seemed iffy at best so I replaced it with a new one

- As for relays, I definitely hear a click coming from the left-most one. Tried all 3 in this spot and they all clicked so they should be good right? Wiring diagram looks like it shows a "switch relay" that feeds the starter relay. I only hear one click, but guessing both should?

- when the key is all the way to start the other electronics go dark, not sure if that's normal or not

Edited November 29, 2022 by sttereve

[sttereve 30]

After reviewing the wiring diagram and wire colors, I think the relay I hear clicking is the kill relay. Gonna trace the safety switches now.

 

Update: all the switches seem good. Might need to take a look a closer look at the relays.

Edited November 30, 2022 by sttereve

[lynnmor 6,850]

Download the Demystification Guide and find the circuit(s) that you want to troubleshoot.  The guide will have simplified drawings that are easy to follow.

[sttereve 30]

Pulled the relays and jumped the switch relay and it worked. So why wasn't the relay tripping? Well, it turns out that despite identical appearance and pin layout the new ignition switch I purchased actually was different and did not have the start position voltage on the right pin. I guess there must be variations of ignition switch that use the same design.

 

Engineers... 

[Handy Don 10,742]

17 hours ago, sttereve said:

Pulled the relays and jumped the switch relay and it worked. So why wasn't the relay tripping? Well, it turns out that despite identical appearance and pin layout the new ignition switch I purchased actually was different and did not have the start position voltage on the right pin. I guess there must be variations of ignition switch that use the same design.

 

Engineers... 

Yep, gotta look closely at model numbers and terminal labeling! '

Glad it's working for you.

Edited November 30, 2022 by Handy Don

[Tuneup 1,416]

Sounds like China strikes again! Today, it's important to get a DMM and test that ignition switch to ensure the proper configuration. Sigh. So glad it's running. My 516H was a garble of wires in the loom that went nowhere. I just assumed it had to be a generic loom from Wheel Horse that was designed to fit different machines.

[Handy Don 10,742]

11 hours ago, Tuneup said:

Sounds like China strikes again! Today, it's important to get a DMM and test that ignition switch to ensure the proper configuration. Sigh. So glad it's running. My 516H was a garble of wires in the loom that went nowhere. I just assumed it had to be a generic loom from Wheel Horse that was designed to fit different machines.

516, 518, and 520 all had Onans but differing amounts of instrumentation and sensors. Wouldn't shock me to find a PO changed the 516 harness for one of the others.

 

Please take careful note: the industry standards that led to differing patterns of switching behavior while using the same switch body and physical connector layout were established by US manufacturers long before any shift to overseas suppliers. Newer suppliers are simply making their products to these standards to remain "plug compatible".

Edited December 4, 2022 by Handy Don