Case 1840 start issue

[Smitty80]

Having an issue where my old 1840 ('94 best I can tell, JAF0152178) won't crank. When I try I hear a slight click, no crank, and then no lights on the instrument cluster or anything for a period of time.

Have good voltage to the ignition switch, and I replaced it since it needed to be anyway (key broken off). I'm only finding 2 fuses, and both are confirmed good and yesterday I replaced the starter. Same issue.
Haven't been able to test voltage to the solenoid yet as that's a 2 person job and it's just been me at this point. The only thing I'm seeing otherwise is a relay behind the instrument panel cluster, could that be the issue and why at some point something resets and I at least get lights on the cluster when I turn the key on (but still no crank)? The wiring diagram says it's an alternator light relay, so not sure if/how that might play into the starting issue.

Any help appreciated.

 

[Alan]

I did a bit of research, and it seems like the issue might be with the main ground or battery cable. The intermittent power to the cluster and the starter clicking suggest there could be high resistance or a loose connection somewhere. Make sure to check the ground strap to the frame and the battery terminals while the system is under load. That relay probably isn’t the main culprit. I hope others with more experience will weigh in.

 

[Smitty80]

I did a bit of research, and it seems like the issue might be with the main ground or battery cable. The intermittent power to the cluster and the starter clicking suggest there could be high resistance or a loose connection somewhere. Make sure to check the ground strap to the frame and the battery terminals while the system is under load. That relay probably isn’t the main culprit. I hope others with more experience will weigh in.

Thanks, I did check the battery cables and everything from the battery all the way to the ignition switch (goes from Bat + to starter to alternator and then back through a 30a fuse to the ignition switch). Agree though on it seems like high resistance somewhere in path.

 

[Alan]

That sounds great, it really helps narrow things down. I’d suggest looking for any voltage drop along that path to identify where the high-resistance area might be.

 

[Smitty80]

Just an update. After all of my voltage checks passed today, I ended up replacing the relay behind the instrument cluster. I'm still not 100% sure why based on the wiring diagram, but it fired right up and working great now. The service manual says it's an alternator light relay, the only thing I can think of is that it does connect directly to the ignition switch and when bad was pulling my start voltage down under any sort of load.

Oh well, it's running.

 

[Alan]

Well done on tracking that down. It’s funny how a small relay can lead to such quirky issues but I’m glad to hear everything is running smoothly now.