Won't start and no headlights

I've spent sometime already looking at this. When I bought it the headlights worked, I drove it home 3 hours on the trailer, then the headlight wouldn't work.

All last summer I dealt with it not starting sometimes. I checked the voltage at the starter wire (light blue there) sometimes it reads 12v, 10v, 4v, or 2v. The light blue wire goes up under the air cleaner, across the front/underside of the battery, then down to a relay. There are 3 relays in a row under the battery. I've attached a picture.

At first I was thinking the splice in the wire might be the problem, but today getting all of the different voltages, I'm thinking it's not the splice because I tried wiggling it while taking the reading and it didn't change.

Last summer I took a piece of wire and would basically jump start the starter going from the Battery + to the starter, it cranks and starts. Sometimes when I've done this, the headlights would start to work.

So, could a bad relay cause these symptoms?

Thank you,
Sam

Relay failure is pretty rare. Is this a 520 we're talking about?

Yes, 520H onan.

1st step, check the main fuse block near the battery. The 15A fuse near the open fuse hole toward the front is the lights, the center fuse is starting and the last fuse is the regulator, relays, and some other things. I sell a ton of those fuse blocks and parts.

I checked the fuses first thing. How do you check the fuse block? Thanks

If you pull the fuse there may be a lot of corrosion in the terminals. You can also try wiggling the fuses around with the headlamps on or while trying to start it.

look at first picture of the relay its stabs are very nasty that is your loose connection source of voltage drop new relay / new base ? if I was betting

After this post, I was out of town on business. I was able to clean the terminals on the relays about 3 or 4 weeks ago. I don't know if it was the cleaning or something else, but it worked until last week. I just checked them again, then used some solder to lightly Tin the terminals. Still no luck.

Intermittent problem, very annoying... Thanks

We need to do some testing while it's down to get it fixed for good, can you give me a call tomorrow while near the tractor?

It wouldn't start Saturday, checked the voltage to the starter, 8.6v or so. Cleaned the fuses AGAIN, then it started up. I'm on a business trip for 2 weeks now. Can you post the part number or link to the fuse block? I'll order one and try that.
Thank you,