98 international 9800 troubleshooting

I believe your new solenoid is working correctly.
You basically proved it by crossing power from the the hot side to the trigger post
(The smaller center post) and you got power on the right post.
The problem to me seems you are not getting voltage on the trigger wire to turn the solenoid on.
Do you have voltage at the smaller center post wire when you turn it on?
Also the solenoid needs to have the case grounded.
It looks like the mount bolts might be broken?
If it’s not bolted to a ground Surface the solenoid won’t trigger and turn on.

 

There is a copper drawbridge between the two big posts. The center lug is to energize a coil that magnetically pulls the drawbridge closed to complete the big circuit. The magnetic control portion uses the chassis ground via mounting tabs instead of another lug. Id say check your ground but i see youve buffed the surface and it clicked when you jumpered it so you have a complete circuit on the control side.

What you are missing is positive voltage on the trigger wire that you say comes from the alternator. Basically this is someones idea of a battery saver. You can only use the devices downstream if the truck is running and charging.

It sounds like your alternator is down. Step1, measure the battery resting volts. Then start truck and measure again. Bring the revs up a bit when you first start to kick the alternator into high charge. You need to see half a volt higher with it running.

If not, hold a piece of metal near the alternator. If you feel magnetism its charging and youve got a downstream issue. If its got no magnetism it isnt charging. Now check for battery voltage on the field terminal and output lugs. If youve got a bulb on the dash for an alternator dummy light, check it. It is in series and if its blown the field will not get any juice, the bulb must work for the alternator to work. You can jump juice off the charge post to the field post to see if the alt will kick on.

 

Sure glad to help. Were narrowing it down then.

If jumping the solenoid control post makes it actuate then youve got a good solenoid and good ground. If your alternator is charging but that trigger wire isnt toggling the solenoid then there is an open of some sort between the alternator hot lug and the solenoid control lug.

Your alternator output post.. How many wires are on it and what does it/they go to?

I cant see why that solenoid is there in the first place if it just powers half the dash.

 

Im seeing two small gauge wires with ring terminals not connected in that photo. Are you connecting the wrong one to the trigger post?

 

Welp, looks like ya got an external regulator which makes resting super easy. You should see AC power on each of those white wires when measured from ground. And 13.x vdc on the output lug.

See if youve got around 13vdc out of the output lug and at the other end of the wire where it mounts to the solenoid terminal. Only think i can think is bad crimp connection or corroded lug at tge post. I have had perfect looking 4gauge cables have ZERO continuity before.

I use a halogen offroad light to load test wires that pass with a meter but logically must be the issue.