SOLVED: 1986 GV ORED not charging and other electrical issues

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SOLVED: 1986 GV ORED not charging and other electrical issues

February 21, 2024, 08:08:29 pm

I recently purchased the GV in my signature. It was an "as is" sale so I'll need to solve the problems myself, some of which I knew from inspection. I've done most of the work on my vehicles over the years but this is my first motorhome. It came with a pile of manuals but, alas, no owner's manual and I haven't been able to find one online.

One thing that I didn't catch was that the engine is not charging the batteries. After the 1.5 hour drive home the engine batteries were down to 11.4 volts. I put an automotive charger on them and got them fully charged. Engine is the Cat 3208.

I knew the generator wasn't working but was able to get it started the next day (points were pitted and badly out of adjustment). After starting it though, I don't see any sign of it generating electricity. It's the 6.5K Onan on propane. It's very hard to access anything on it and I'm not sure where I can check for output. It appears to start off the coach batteries and they were run down quite a bit with the multiple attempts at starting it.

I don't have access to 50 amp shore power but was able to use adapters to plug into a standard AC outlet. There is a charging unit that appears to be aftermarket that showed it was charging at 20+ amps most of the day but neither battery bank seemed to be going up in voltage.

I can usually figure these things out but without any wiring diagrams and a totally new to me type of vehicle, I'd really appreciate it if anyone has some suggestions that might save me time.

Re: 1986 GV ORED not charging and other electrical issues

Reply #1 – February 21, 2024, 09:38:27 pm

Congratulations on your purchase. The search box at the right top of this page opens up a lot of information. In the media section you may be able to find previous downloaded wiring diagrams.
How do you eat an elephant? One bite at a time. In other words break each problem into it own section. I find making a list beneficial to me. We all love pictures. Start with the simple problems and work your way through. Although im not much help once you start breaking up the problems the answers will follow.
Alternator issues
1 does it have a sense wire for the regulator?
2 belt slipping
3 Charging cable condition
4 Isolator condition and operation
Same with the Generator

Re: 1986 GV ORED not charging and other electrical issues

Reply #2 – February 21, 2024, 10:30:20 pm

I have the same bus.
Start with the basics. The ground cables are my usual point of interest. Clean the grounds under the stairs and near the engine .
Ive had the excite wire fail from the fuel run solenoid to the alternator. about 10 in wire .
This wire may run from any point that is hot in" run" only .
Next failure could be the battery isolator . It is mounted on the engine room bulkhead , just over the fuel filters. . It will have 3 wires if OE. Test the end cables to match the batteries. Disconnect one set and determine which wire does what. Connect the 3 cables together. test touch of course to avoid the smoke thing. Now all of the batteries are linked . If you show charging with this connection. You may have a faulty isolator . All of the batts will discharge together also. In my case , i leave my batteries separate due to my solar system charging my house batts.
Edit. Use the boost switch to aid the starting and to avoid running large amp load through the small charge cables at the isolator.

Re: 1986 GV ORED not charging and other electrical issues

Reply #3 – February 22, 2024, 08:58:11 pm

You've received some good information on what to check for your charging issue. One of the best investments you can make is solar power. More is better but it doesn't take much to charge your house batteries and you can use a trickle charger to keep your starting battery (or batteries) topped off.

Re: 1986 GV ORED not charging and other electrical issues

Reply #4 – February 26, 2024, 02:04:00 pm

Thanks, everyone. I did find an owner's manual in the "media" section which has helped. I had guessed the switch on the batteries was to allow combining the banks to start the engine, but according to the manual, it is used for storage. Once I closed that switch, shore power will charge both banks. One problem solved.

With the engine running there is 0 voltage on the middle post of the isolator. My understanding is that is the output from the alternator. The other 2 posts have the same voltage as their corresponding battery banks. I don't see any way to get to the alternator without removing the whole air filter system, so I plan to do that today.

My understanding is that there is a relay or something that selects whether the AC circuits run off the generator or shore power. Does anyone know where that is? That might help me tell if the generator is working. The generator is pretty important for we will mostly be parked at a construction site that will be off-grid for the foreseeable future. We'll be about a mile away from a place we can dump sewage and refill water and plan to drive back and forth when needed.

Re: 1986 GV ORED not charging and other electrical issues

Reply #5 – February 26, 2024, 06:15:44 pm

Main engine running and no voltage on center post of isolator means bad ioslator

Re: 1986 GV ORED not charging and other electrical issues

Reply #6 – February 26, 2024, 07:23:02 pm

The center post should have voltage from the alternator. If no voltage check the alternator for voltage at the positive terminal on the alternator. If you raise the bed you should be able to access the alternator.

Re: 1986 GV ORED not charging and other electrical issues

Reply #7 – February 26, 2024, 08:14:33 pm

In my 03 U320, a just rebuilt alternator had no voltage on the center post. Moved alternator output to one side, plenty of voltage. Replaced isolator, all is well.

Re: 1986 GV ORED not charging and other electrical issues

Reply #8 – February 27, 2024, 01:15:19 pm

Yes. My isolator was drawing some amps for no reason. I simply connected the alt and engine batt to the same end post.

Re: 1986 GV ORED not charging and other electrical issues

Reply #9 – February 28, 2024, 01:13:35 am

I posted some pictures in my album of the alternator and a relay(?) that is wired to the small terminal on the alternator. It looks cleaner than anything else in there so I assume it is not OEM.

Re: 1986 GV ORED not charging and other electrical issues

Reply #10 – February 28, 2024, 06:44:57 am

Quote from: Uncle Pa – February 28, 2024, 01:13:35 am

I posted some pictures of the alternator and a relay(?) that is wired to the small terminal on the alternator. It looks cleaner than anything else in there so I assume it is not OEM.

Looking at your photos, what can we learn?

At first glance, I would say the alternator is not original equipment. This is not surprising or unusual on the older model coaches. Problems DO crop up when a replacement alternator is not the correct type, or is improperly wired. Both issues are possible in this case. It would be VERY helpful if you could see, or better yet get a photo of, the model number ID plate on the alternator. We need to find the (online) wiring diagram for that particular model alternator to figure out how it should be wired to work on your coach.

Did you get a paperwork file with your coach? If yes, look through the file to see if there is ANY mention of the replacement alternator model number.

In order to understand why your coach needs a particular type of alternator, you should search (on the Forum) the term DUVAC. This term refers to an alternator with the special wiring required to function in a charging system that employs a diode based battery isolator and two separate battery banks. Understanding the term DUVAC will help you trouble shoot your charging system. See the link below for a simple diagram of a DUVAC alternator:

https://www.dixie-electric.com//tsb/TSB_704.pdf

The relay in your photo, as you deduced, is definitely not OEM. It may have been installed by the prior owner in a (possibly futile?) attempt to make the replacement alternator function. We can't figure out its intended purpose until we have identified the alternator model.

By the way, that mystery relay is mounted on the cruise control panel, which IS original equipment. If anyone asks you what kind of cruise control you have, you can now confidently answer "Bendix Cruise Control with Air Throttle". Trust me when I say this question will come up sooner or later. See the link below for a discussion of the Bendix system:

air throttle problem

Re: 1986 GV ORED not charging and other electrical issues

Reply #11 – February 28, 2024, 06:52:00 am

Quote from: Uncle Pa – February 26, 2024, 02:04:00 pm

With the engine running there is 0 voltage on the middle post of the isolator.

Now that you have the alternator exposed, can you start the engine and measure the voltage on the alternator B+ output post? This would be the large post where the large red cable is attached. This is the starting point of your charging system circuit. Let us know what you find.

Re: 1986 GV ORED not charging and other electrical issues

Reply #12 – February 28, 2024, 09:55:25 am

You will need to ID the alternator . Take , or send that pic to a rebuilder and then source the schematic . The relay is most likely an excite wire circuit. With power coming from a keyed circuit.
In my case, the key on power came from the fuel solenoid , at the edge of your picture. The round tower thingy.
You could also trigger the relay and see what catches fire

Re: 1986 GV ORED not charging and other electrical issues

Reply #13 – February 29, 2024, 03:11:15 pm

Thanks again, everyone. I didn't get any service or repair records with the coach.

With engine running there is no voltage at either of the red wires on the alternator. The only label markings I have found on the alternator are the characters you can see on the brush cover. I did a search on what looks like a part number (YY18L25) but found nothing.

Wouldn't a quality made part have identification on it? Is it worth the trouble trying to find out what this is if it is some cheap replacement? I prefer to fix things right even if it costs a little more. Any ideas on what it would take to restore it to OEM quality or install a proven superior system? Or is it realistic to experiment by running a wire from the fuel solenoid (as in Mike's setup) to each of those 3 smaller posts? Could that damage anything?

That being said, the generator is of more immediate concern. We don't plan to take any long trips until next year and we can easily recharge the batteries after driving it back and forth to the dumping station if the generator was working..

Re: 1986 GV ORED not charging and other electrical issues

Reply #14 – February 29, 2024, 03:35:12 pm

Quote from: Uncle Pa – February 29, 2024, 03:11:15 pm

1. Or is it realistic to experiment by running a wire from the fuel solenoid (as in Mike's setup) to each of those 3 smaller posts?
2. Could that damage anything?

1. Connecting a HOT wire to any of the three small posts is not a good idea.
2. Yes, it could damage something.

If you can't ID the alternator, then obviously you can't find the wiring diagram.

Let us assume (always chancy) that your alternator is a simple generic "1 wire" model. In that case it would only require two basic connections to operate: connection through the B+ post to a 12 volt battery, and connection to chassis ground (either through the alternator mounting bracket or the NEG post on the alternator). You already have the grounding connection. What you are missing is the connection to a 12 volt battery. At present, the B+ output post on the alternator is connected to the center post on the isolator. That center post is isolated from the batteries - hence the name "Battery Isolator". The alternator cannot "see" the batteries.

If you wish, you could try a simple experiment. Go to the isolator. Remove the ALTernator cable from the isolator center post, and attach to the same outer isolator post that is connected to the chassis (engine start) battery. When that is done, the alternator should now be able to "see" the voltage on the start battery. REMOVE the small red wire that is connected to the small post on the alternator. Start your engine. Check to see if the alternator is now producing voltage at the large B+ output post.

If it IS producing voltage, then your problem is solved. The alternator will charge the chassis (engine start) batteries. If you want to charge both battery banks with the alternator, turn on the boost switch.

If alternator still doesn't produce any voltage, then further trouble shooting will be required.

Re: 1986 GV ORED not charging and other electrical issues

Reply #15 – February 29, 2024, 03:44:06 pm

When my main alternator fails, I will figure out how to install a GM 28 style in place of the OE unit.

Many have gone through the hoops to use an OE style alternator to maintain the dual battery charging system . These should come up in a search . It requires a good isolator and cable system .

I dont see the reasoning for that in my case. I need parts that are available, because I cant afford the down time .
I have removed the isolator , added a one wire GM alternator under the engine, added solar to run most of the bus, etc. I seldom use the boost switch, but make sure that it works every now and then.

Also, I believe that the short excite wire was OE , to my OE alternator.
The gen set runs into a transfer switch , near /or under the the closet floor.
There is also some sort of inverter near there, also . On paper . I have never seen mine . If i need the microwave, I have to have the genset run or plug in .
The charger for the house batts may be in the wet bay, mounted to the ceiling. It should have a simple receptacle/near /above it to plug into the 120 V system . The dampness of the bay will lead to its demise. I have used a large simple( not intelligent) battery charger in there but have a standard RV charger, power supply to install soon.

I seldom plug in with the solar . But it needs some sun to run the fridge and mostly sun to the run the AC .

Edit, I thought that the bypass of the isolator was tried . Do that first .

Re: 1986 GV ORED not charging and other electrical issues

Reply #16 – February 29, 2024, 07:18:02 pm

In lieu of identifying the alternator by part number, please tell us EXACTLY what wires connect to the alternator and what marking are on the alternator by each connection.

Some possible/likely markings:
B+
-- (ground)
Sense
Ign

Once identified, we can tell you what readings you should expect at each connecton.

Re: 1986 GV ORED not charging and other electrical issues

Reply #17 – March 04, 2024, 05:08:59 pm

Quote from: Chuck & Jeannie – February 29, 2024, 03:35:12 pm

If it IS producing voltage, then your problem is solved.

Almost, but close enough. I was hesitant to try the experiment for I feared what did happen might happen. Despite 3 days of PB soaking, the main battery post on the isolator broke off when I tried to remove the nut. The alternator nut came off fine, but I don't think I can connect them there for that would allow the coach batteries to try to charge off the engine batteries if I understand the isolator correctly. Anyway, with the alternator directly bolted to the cable from the main batteries and hanging down in air, it is now putting out 14.2v. I did not take the smaller cable off, and all 3 of the smaller posts show 7v. I can take it from here but am open to suggestions on what is best. I can just work out some way to connect those 2 cables, insulate the connection and zip tie it to something down there, or I can replace the isolator. But since in that configuration, the isolator wouldn't really be doing anything, that seems like a waste unless there is some way to wire it up to work as originally intended.

As for the markings, all I can find on the alternator is NEG OUT on one side and POS OUT on the other on the housing as raised letters from the casting. I cannot find any markings near the smaller 3 posts.

As for the generator. I found the transfer relay at the foot of the bed and it is getting voltage from the generator, but the relay is not switching to use generator power when the shoreline is unplugged and only the generator is running. What causes that relay to switch from one to the other? Actually it is 2 relays, one for the hot and one for the neutral, but both appear to be stuck on the shoreline side. By "stuck" I mean electrically, not physically. With all power off, they both move freely.

Re: 1986 GV ORED not charging and other electrical issues

Reply #18 – March 04, 2024, 05:41:52 pm

Quote from: Uncle Pa – March 04, 2024, 05:08:59 pm

1. Anyway, with the alternator directly bolted to the cable from the main batteries it is now putting out 14.2v.
2. I did not take the smaller cable off, and all 3 of the smaller posts show 7v.
3. I can just work out some way to connect those 2 cables, insulate the connection and zip tie it to something down there
4. or I can replace the isolator.
5. But since in that configuration, the isolator wouldn't really be doing anything, that seems like a waste unless there is some way to wire it up to work as originally intended.
6. As for the markings, all I can find on the alternator is NEG OUT on one side and POS OUT on the other on the housing as raised letters from the casting. I cannot find any markings near the smaller 3 posts.

Referring only to your alternator situation, my opinion on your statements (above) is as follows:

1. Wiring the alternator directly to a battery makes it work. Good. This proves it is "self energized" and does not require a "Excite" wire to operate.

2. IMO that small wire is doing nothing. I would again encourage you to remove it and see if the alternator still works. If it does, leave the small wire disconnected.

3. IF by "main batteries" you mean the engine start batteries, then you already have the alternator wired to work. Just do as you said - insulate the connection and tie the cables down so they don't flop around.

4. The isolator is broken, so remove it. No need to replace it.

5. Your coach will work fine with the alternator wired direct to the start batteries. You DO need a working BOOST solenoid if you want to be able to charge both engine start and coach batteries with the alternator.

6. If the alternator needed a small wire of any kind attached to one of the small posts, they would be marked in some way. I do not believe you need the small red wire, but you do what you think is best.

The photo below shows an alternator with a design similar to yours (regulator is different). The three small unmarked posts are labeled AC terminals. Also known as "AC taps". These posts should put out roughly one half of the DC voltage being generated by the alternator, or around 7 volts. Exactly what you report. These posts are not normally connected to anything except perhaps bench test equipment.

Re: 1986 GV ORED not charging and other electrical issues

Reply #19 – March 04, 2024, 07:27:18 pm

Thanks so much! It does work fine without the small wire attached.

Should I mark this as solved and start another topic for the generator issue?

Re: 1986 GV ORED not charging and other electrical issues

Reply #20 – March 04, 2024, 09:07:32 pm

Sounds like someone put on a truck alternator instead of a DUVAC enabled alternator.

Re: 1986 GV ORED not charging and other electrical issues

Reply #21 – March 04, 2024, 09:52:38 pm

Quote from: Uncle Pa – March 04, 2024, 07:27:18 pm

Should I mark this as solved and start another topic for the generator issue?

Yes, starting a separate topic for the generator would be a good idea.

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