Electrical schematic on 80's Rambler

[Daveputt]

Originally Posted by Dave78Chief

I would stick to one problem at a time or you will get confused

Funny you say that! It has been more frustrating than I expected. I have a dozen or so issues that I am tackling, some related some not.
I am fearful that if I don't look at the electrical part holistically then I might not find the problem since I don't know RV systems. If the alternator goes bad on a car its easy to diagnose. If its on an RV, would a similar symptom appear on the isolator (or something else)? That's why I post a plethora of questions.
Last night I gave up on the more complicated tasks and put the vent covers on my LR and Bath vent. I needed a win, no matter how simple it is! I also turned the RV around check my drain problem (on another post). Drains work perfectly know that I am down hill not uphill...who knew?!
Funny things happen on the electrical side, may be related to 1 thing, may be multiple. I am getting the coach batteries tonight and check my generator oil level. It may help limit some of the odd problems I am seeing.
Some things may not be odd if the RV is designed that way. For instance I didn't know that both AC units wouldn't run on shore power. Or that the generator should run both units. These are things I am figuring out while I troubleshoot.
I also am not big on handing the keys over to a mechanic just yet. I really want to learn all these systems so I can work on it myself. I will give up eventually if I don't get any progress.
Also trying to find out why 1 leveling jack isn't retracting...the list gets longer and longer!

[ahicks]

Re: the alternator. Mentally, figure it just like a car or pickup, and get it working that way. Then, again mentally, hang the RV system piece on to the (now functional) car/pickup system.

Same story as earlier. Looking at the whole thing is a mess. Break it down into pieces you can get your head wrapped around easily.....

That was the thought behind putting all 3 of the isolator wires on one post. Getting that out of the circuit eliminates many potential issues.

Installing the coach batteries at this point only complicates......stuff?

[Dave78Chief]

Hopefully you can use this as a guideline for how this all works



Dave

[Daveputt]

Dave, that is the perfect schematic! Many thanks
I removed the alternator tonight. I am going to take it get tested tomorrow.
Strange, the plug was not connected to anything.
I had 3 wires in total connected directly. 1 was a battery size cable, 1 went to the aux start solenoid, 1 went to the wire joined with the battery solenoid. I can't tell from my pics which one was joined with the battery cable. I should be able to check again to decipher.
I looked for a lose connector/wire to reconnect it but nothing was around. I will look in day light but I am 95% sure nothing is around. Any chance this was omitted and the 3 cables were all it needs?

here are a few before I removed it.

[Dave78Chief]

That appears to be a 75 amp 27SI alternator. It only uses 3 leads

B+ - Two Red 12 gauge wires - This will go to the ALT terminal on the diode isolator. Purple wire on my drawing

2 wires on plug
14 gauge Red wire (B) - Sense wire goes back to chassis battery B+ (bypass diode isolator) [top of alternator on my drawing]
16 gauge Brown wire (A) - Goes to idiot light on dash. Has to be connected for the internal regulator in the alternator to work properly [not shown on my drawing but still needed]

Dave

[ahicks]

Regarding the diagram, some detail that might head off something that may provide some confusion (without adding even more, hopefully?). I mentioned earlier that relays may be similar in appearance, but wired way different internally? Those shown in the diagram are a good example. Shown here are the type where the solenoid windings are grounded through one of the 2 smaller posts. That might not be the case with the relays on this MH. It would appear (from the pics) they might be grounded through the metal relay mounting strap?

One other thing, the "sensing wire" shown leading to the alternator (in the diagram)? I believe that wire is switched by the ignition switch. It's only hot if the key is turned on. If left on full time, it could drain your battery. This wire is eliminated altogether on later model alternators. Just had the alternator rebuilt on our coach, and a newer style voltage regulator was installed - that does not use the once required "sensing wire".

Last, the relay marked "Battery Isolater Solenoid" is the one that SHOULD be closed with your emergency start switch. As you can see, it should not turn the engine over.

[Daveputt]

I took the alternator to a repair shop and explained what is happening to the RV.
The alternator tested ok. We did some extra tests to duplicate my wiring and we saw the same 12.1V that was on my RV. He changed the wiring and it jumped to 14.2V.

He gave me a new wiring harness and some diodes. This would explain the constant drain and fix it. It also sounds like what the 2 of you have been telling me in the last post. Fingers crossed it goes together and works!

Hoping for a win!

[ahicks]

Pretty sure it will, but if it doesn't, at this point there's no question about the alternator being blown. You should be able to build on that fact. That's progress. Good job!

[Daveputt]

Still working on my electrical problem. I couldn't get the alternator to charge like the rebuild shop was able to do on the bench. I'm going to go back on Monday and talk some more.
I am doing some reading on my generator and I'm trying to figure out if I have to manually switch the HR from shore to generator power. Where would this switch be located if I have one?
I have 2 switches on top of the back right side of my generator on a metal enclosure. Hey feel like light switches and I can read them if they are labeled.

[Dave78Chief]

While 80's HR's had a Inverter/Shore switch, I am fairly sure you do not have a shore/generator switch. You have to plug the shore power cable into the generator recepticle which I believe is in the shore power cable compartment.

Dave

[ahicks]

The 2 switches are likely circuit breakers. Did you get the gen set running again?

The land line/gen set selector could be manual or automatic. They were switching back and forth during the period when your coach was built. Much of how that decision was made had to do with options included when the coach was built (dual air and big gen set likely has one, but nothing set in stone). As Dave mentions, you should be able to spot a receptacle that the land line will plug into to get gen. power pretty easily if it has one. OR, if there's an automatic cross over relay, many times those are found in a grey box right on the coach end of the land line. Note many of those have time delay relay built into them. Thought there being to give the gen set a minute to warm up prior to getting a load placed on it. Point being there may be a minute or 2 delay prior to you getting interior power after starting the generator - assuming those circuit breakers on the gen set are in the "on" position! ;^)

Keep reading!

[Daveputt]

Can't say I found a solution yet but I am getting closer. I DO have a female socket built into bumper where shore power cord resides. I haven't had time to plug it in and try the generator.
On the parasitic drain front, I was able to get it down to .09 amps from 3.5A. I turned off all the 110 breakers and pulled the fuses in that area. I assume these distribute the 110 to the 12v lights/other systems in the coach.

What was strange, it was 3.5 amps and then i plugged in the shore power cord and it cut in half. I pulled the fuses and breakers and saw another drop. I toggled the power selector switch off (options are inverter/off/generator). I also turned off the 2 switches on generator and saw another drop. It was random.
After I got to .09A I wasn't able to get back to 3.5A. As if there is a capacitor in an inverter or converter that took 15 minutes to reach capacity and stop draining the batteries.
Also I found a cooked wire from alternator to voltage regulator. It was the ground wire and the other 3 wires were cut off from the voltage regulator. Why do I have this? Aren't these built into alternators since the 70's?
I'm piecing it together 1 hr at a time when available. Slowly but surely!

[Daveputt]

And another thing to note. Alternator is not giving me a charge yet. Need to work on the wiring.
I idled the other day for 15ish minutes and the battery dropped from 12V to under 10v.

[Dave78Chief]

I am fairly sure you AC setup is like this:


The stock GM Alternator uses a internal regulator.

Dave