I replaced my isolator and auxiliary starter solenoid and small 5 pin relay today. The coach won't turn over, batteries are good, I'm thinking I landed a wire wrong somewhere in my replacement. I had disconnected all batteries when doing said replacement. Do I need to remove all battery post connectors or can I just remove the negative side? The coach started fine before this so I'm not exactly sure where to start.
Removing the negatives is fine.
Since you replaced it, the the AUX START solenoid wiring is suspect. The small post on the solenoid should be hot (12V) when you turn the ignition key to START.
Link below to post where I list the various items required to get a mechanical engine coach (like the U280) to crank (turn over).
Starting trouble. Solenoid? Isolator? Something else? (https://www.foreforums.com/index.php?topic=42645.msg427588#msg427588)
I do get 12 v on the small post when ignition is turned, does it need to be turned fully or just to the on position? The ignition. Something is clicking. It seems like it's over my head, possibly under the bed. On the boost solenoid I have voltage on both sides of the big post but on the starter solenoid I only have voltage on one side. Should I have voltage on both? This is when the key is off
1. Should get 12V on AUX START solenoid small post when ignition key is turned fully to START position.
2. BOOST solenoid should have 12V on both large posts (assuming both battery banks are fully charged).
3. AUX START solenoid should only have 12V on one big post with ignition key OFF.
If AUX START solenoid is a 3-post model, it grounds through the mounting bracket.
If it is a 4-post model, it requires a separate ground wire.
Either way, be sure the AUX START solenoid has a good clean ground.
That was my problem, new solenoid was a 4 post, I didn't have it grounded. It starts now, but I'm not sure I'm getting good charging. Checking the new isolator posts 13.5 on the house batteries,12.5 on the starter batteries and if I test the input on the isolator from the alternator it reads 2.9? Voltmeter in dash is just below 12 while we sit idiling. Glad it's starting, but would like the charging issues to get better
That obviously is not right - the alternator input post on isolator should show 14+ volts with engine running.
If your alternator has a SENSE terminal, check the connections at each end of the SENSE wire.
The SENSE terminal on the alternator should be
always hot and show the same voltage as you read at the POSITIVE post on the start battery.
If your alternator has a EXCITE terminal, check the wire connections at both ends. The EXCITE wire should be hot
only with ignition key ON.
Check the connections at each end of the large cable that goes from alternator output terminal (B+) to isolator. Clean and tight?
If your alternator has a separate ground cable, check to be sure it has clean/tight connection at both ends.
What about testing voltage directly at the alternator? With motor running, red + terminal on meter on positive terminal of alternator and black lead to ground shows 2.3 volts?? Am I probing the wrong contact points?
Is the red + terminal a large wire and where are you getting ground. Even if the alternator was dead it wouldn't read that voltage if you were able to start the engine.
What alternator model/brand do you have, and what isolator model/brand did you put in for the replacement? This might help to figure this out. Pictures are always good...
I suspect an erroneous reading on the voltmeter-- likely to inadequate contact with clean ground.
I have a Leece Neville alternator and just replaced my isolator with a Victron Argofet 200 amp. I have been having charging issues, had the alternator checked, the voltage regulator was bad, had that repaired, still had a problem, I thought maybe it was the isolator so I replaced that and both my auxiliary start solenoid and my boost solenoid and my resettable breakers and my relay. Brett, I'm thinking it is the ground as well, will try to track that down tomorrow. Any and all advice is welcome.
Victron Argofet isolator is a good choice - and - IF you decide to replace the alternator, this isolator with the ignition excite terminal is compatible with a Delco alternator. Other members (myself included) have installed a Delco alternator with good results.
A recommendation would be the 200 amp 28SI. Word of caution, there are cheap China knock-offs that say "replaces Delco..." or "Delco type...", be sure the alternator is genuine Delco.
Also a recurring point of confusion when installing a Delco alternator with an isolator - the "I" terminal is NOT the ignition excite connection, you need to use an isolator with the ignition excite terminal.
I just replaced the alternator 2 years ago at FOT and just had it serviced at a local "old school" alternator shop. They said the voltage regulator was bad and replaced it. We took a few, short, local trips, still seemed to have a charging issue. I took the alternator back to the shop to make sure it was still good - he said all is well. Finally got parts and time to replace them: isolator, breakers, solenoids. That whole isolator area looked tired and worn. So... I'd like to make work with what I have which is all new except for the alternator is 2 years old. Next step is running new sense wire and checking for good ground. Electrical gremlins are working me hard.
Definitely run new wires. If you have a good sense signal and a good ignition signal then that alternator will work.
Check your grounds where they tie in to the frame,should be 3 or 4 bolted to the frame,take apart and clean.
I can't help with this problem but, as a general rule , before I disconnect anything on the coach, I take multiple pics of the wiring. I then look at the pics to make sure I can re-attach them correctly before I disconnect anything. I especially make sure I can tell the color coding. This has saved me a lot of grief. I will also keep the pics in case I run into problems later, like a broken, failed or burnt connection.
TOM