MC9 charging wire route from alternator.

neoneddy · January 03, 2019, 09:51:50 AM

I've been avoiding taking my bus down to the shop until I've exhausted all self diagnosis for my alternator issues.

I'd like to trace the route from alternator to the batteries. Early in our bus adventures I had been pulling too much juice from a poorly crimped connection and burned a wire from battery to house battery. So I'm figuring maybe I have a burned out connection in the main run of wire someplace.

As some of you know I run the Victron equipment with VRM logging, in effect this logs alternator output and I've been able to review the data logs from this summer and I noticed slow degredation of output with spikes of full output . As recent as late October / early November I had 1 session where I got full power, I adjusted the regulator down to 28v and was satisfied. Then back to normal.

I'm starting to think I have a bad ground or a bad positive someplace. I know even a charred crimped connector will allow some flow , which is what I'm experiencing.

I replaced 2 diodes this fall in the 50dn , it's either this ground / positive issue or bad windings. It's going to be 40 this weekend in MN, I'm planning to do some digging. I might by pass everything to test it and run 00 wire from alternator to battery both positive and negative.

bevans6 · January 03, 2019, 12:55:12 PM

It's probably identical to my 1980 5C. 1/0 wire for the ground to the chassis. 1/0 wire from the alternator terminal to the rear junction box stud, then 1/0 to the large stud on the engine bay wall, passenger side. 4/0 from the engine bay stud to the main battery disconnect switch on the forward bay wall. 4/0 wire to all the batteries from the switched side of the switch. 4/0 (might be 2/0) from the engine bay stud to the starter motor. 1/0 from the unswitched side of the main disconnect switch to the AC junction box (roof, forward drivers side luggage bay), and somewhat smaller cable forward to the main electrical panel bus bar. So the charging path to the batteries uses a combo of 1/0 and 4/0 wire, Alt to rear junction box to main stud in engine bay to disco switch to batteries. Disco switch has been known to go high resistance with corrosion.

neoneddy · January 03, 2019, 12:59:05 PM

Thank you! sound like plenty of points to check.

That 4/0 run from the engine firewall to battery disconnect. Does that go in the central tunnel? I suppose that's a single piece, so no sense in having to inspect all of it.

Geoff · January 03, 2019, 04:53:37 PM

Quote from: neoneddy on January 03, 2019, 09:51:50 AM

I'd like to trace the route from alternator to the batteries. Early in our bus adventures I had been pulling too much juice from a poorly crimped connection and burned a wire from battery to house battery. So I'm figuring maybe I have a burned out connection in the main run of wire someplace.

As some of you know I run the Victron equipment with VRM logging, in effect this logs alternator output and I've been able to review the data logs from this summer and I noticed slow degredation of output with spikes of full output . As recent as late October / early November I had 1 session where I got full power, I adjusted the regulator down to 28v and was satisfied. Then back to normal.

I'm starting to think I have a bad ground or a bad positive someplace. I know even a charred crimped connector will allow some flow , which is what I'm experiencing.

I worked on a 4104 that had a ground wire to the frame that looked good. When I took it apart there was hidden rust that stopped the connection. Yes, check all connections!

neoneddy · January 03, 2019, 09:35:04 PM

I had a starter ground terminal that kept smoking this year, I cleaned it up real good and put some conductive grease on it. Works great now.

I'll know more tomorrow

buswarrior · January 04, 2019, 03:39:03 AM

The good coach refurbish companies pulled all new cabling automatically...

The jumpy output fits with internal corrosion, vibration/bumps changing the connectivity.

Inspect the accessible engine room cabling, think really hard about disassembling the junction, and splitting the insulation/heat shrink on cable ends in search for the green/black corrosion.

Have the materials on hand to re-seal to your satisfaction, but I bet you find some cancer in cable ends, or split insulation.

Happy coaching!
Buswarrior

neoneddy · January 04, 2019, 03:24:13 PM

Well, I found that main stud, it was not happy, very greasy, cleaned it up real good. Found the starter lug was welded to it's washer.

Still not outputting full power. I found the other stud on the other side, it's pretty rusty, I'll clean that one and the ground strap up next.

I did use it as a chance to take it out and fill up with fuel. There is a diesel war a few cities north, filled up at 2.49, everything around here is 3.00

richard5933 · January 04, 2019, 03:30:37 PM

Not sure if the MCI is anything like the GM in this regard, but don't overlook the ground studs located around the bus. I've got one at nearly every place with a terminal block (next to driver, in HVAC bay, engine bay, etc.)

Doesn't take much for these to add resistance to the circuit. A little emery cloth and DeOxit goes a long way.

Curious to see what you come up with in the end.

chessie4905 · January 05, 2019, 12:57:02 PM

On the GMC's the starter main lead connects to a through the firewall stud at engine firewall. If either side of the stud/ wire connection has corrosion, you will get reduced current to starter.

bevans6 · January 06, 2019, 05:27:57 AM

How are you testing the alternator output? What loads are you putting on it to cause it to try to maximize it's output? While the 50DN is rated around 6500 watts, in use the bus only has a maximum of around 4500 watts of possible load with everything on. What levels of output are you seeing? Regardless of it's capacity it will only output the load that's being placed on it. If anything else in your system can also supply some power, it might be doing so during your tests.

neoneddy · January 09, 2019, 11:52:39 AM

I know I'll get some flak for my measurements, but essentially I'm using the BMV Shunt for my house bank as a measurement. The Victron CCGX when told it has a DC system will do the math and figure out "Oh there is x amps / watts coming in from an external DC source. Since I've owned the bus, it would always show me what sort of watts I was getting coming in from the coach side, then it stopped showing 1000 or 2000 watts coming in late July of this year, now it's 200-300 with RPMS up.

I haven't had much time to mess with it this week. I might take a look at the diodes again. If the new ones are also burned up, could mean a winding is bad or something else.

richard5933 · January 09, 2019, 12:12:19 PM

Quote from: neoneddy on January 09, 2019, 11:52:39 AM
I know I'll get some flak for my measurements, but essentially I'm using the BMV Shunt for my house bank as a measurement. The Victron CCGX when told it has a DC system will do the math and figure out "Oh there is x amps / watts coming in from an external DC source. Since I've owned the bus, it would always show me what sort of watts I was getting coming in from the coach side, then it stopped showing 1000 or 2000 watts coming in late July of this year, now it's 200-300 with RPMS up.

I haven't had much time to mess with it this week. I might take a look at the diodes again. If the new ones are also burned up, could mean a winding is bad or something else.

Do your chassis batteries still maintain charge?

Can you still run all the necessary equipment on your chassis system? (headlights, HVAC, etc)

You're talking about a suspicion of a reduction in output on your chassis alternator of huge proportions. Assuming a 24v system, you're dropping from 80+ amps down to 10+ which hardly seems capable of powering the chassis systems.

What I'm getting it is that if your chassis systems are still doing okay, then I'd question this as a method of measuring alternator output. Possibly as a measure of input going to your house battery bank, but there are lots of things that affect that (from bad batteries and on...)

neoneddy · January 09, 2019, 12:28:14 PM

QuoteDo your chassis batteries still maintain charge?

It drops to around 24v or so if I let it, then maintains there, I have my solar system always on, so it usually helps.

QuoteCan you still run all the necessary equipment on your chassis system? (headlights, HVAC, etc)

Yes, I run LEDs for everything (headlights too) , only thing that draws the system down to 24v . I've attached the logs from a drive last friday where I ran the HVAC intermittently. Everytime the voltage drops to 26, the HVAC fan is on... when I turn the fan off it recovers, I was only pulling in 100-200 watts in solar. I had all my lights on, but with all LEDs, it's not much.

QuoteYou're talking about a suspicion of a reduction in output on your chassis alternator of huge proportions. Assuming a 24v system, you're dropping from 80+ amps down to 10+ which hardly seems capable of powering the chassis systems.

Well I found 2 burned out negative diodes in August. If they burned out due to windings, I think that makes sense. I'd say I'm running at 1/3 capacity. Seeing as how there are 3 sets and 2 were bad, that checks out. I did replace them, but haven't rechecked.

QuoteWhat I'm getting it is that if your chassis systems are still doing okay, then I'd question this as a method of measuring alternator output. Possibly as a measure of input going to your house battery bank, but there are lots of things that affect that (from bad batteries and on...)

I'm considering adding a hall sensor on the alternator output wire so I know that I know what it's putting out.

I should add I've also tried going full field bypassing the voltage regulator, no dice there. But I need to double check that as well.

EDIT: I'm going to fire it up today and run some AC electric heaters from the house side, that's the best way to measure the flow I think, vs the HVAC blower. Ultimately this is how I found out it stopped working right, the roof ACs kept draining the system and it wasn't replenished (We only used 3000 watts)

Jim Blackwood · January 10, 2019, 11:39:57 AM

I've always felt that the best way to keep tabs on your charging system is to use both a voltmeter and an ammeter. Your wattmeter just combines the readings of the two which is a good indication of overall power but somewhat lacking.

Look at it this way and compare it to water: Voltage is the pressure. In fluid terms it's how tall of a hill you can push to the top of. Amperage is the flow. How fast will you fill the bucket. Put the bucket on the hill and it takes both to fill it. Multiply one by the other and now you have the volume. Wattage in this case. So with both gages, a little thought will often tell you whether a problem is at the alternator or the battery.

You can also use your wattmeter and divide by the voltage to get your current. Buswarrior is right, your readings indicate a dramatic decrease in charging current.

With a more complex system like a bus you might need multiple gages to pinpoint problems. Happily, modern high current ammeters use a local shunt to carry the heavy current and a small signal wire to go to the gage.

Jim

neoneddy · January 10, 2019, 11:48:50 AM

Tested this morning... engine running, applied a load on the house side, 1,100 watts or so, saw 800 or so coming in from the coach side, but voltage kept dropping wich tells me it was mostly battery not alternator. Voltage got to 23 before I stopped.

I've got a line on a used 50DN here locally for $250, anyone want to come help install it?

I'm still confused how sometimes I get spikes of current... I'm pretty sure I just overworked it a few times. Tried running both ACs with a drained house battery bank (from boondocked at a rest stop or something). I looked in the logs and saw over 4,500 watts coming into the house side more than once.