[Charles]

What is a secondary charge indicator?

More to the point, what does the voltage gauge indicate when the light comes on?

A low voltage can be the result of a failed alternator, it can also indicate a failed voltage regulator. What test was done to show the alternator had failed and the issue was not something else?

Be specific as to your coach system. Single or multiple alternators, voltages, etc. Some coaches have two alternators in your vintage, such as a 24V for the chassis and a 12V for the house. But if the house is a 24V one then a single 50DN alternator feeding power to house and chassis batteries through an isolator may be used.

[CHIP]

Jon, the secondary alternator is the one I assume charges the engine batteries. The big 50 DN is the 12 volt system. The alternator I replaced was a 24 volt unit.

I couldn’t get a read on voltage off the old unit so i replaced it with a new one.

New one does not read any voltage either when the engine is running. I must not be doing something right when taking the reading.

This is a 2001 Marathon unit. Detroit 60.

The indicator light is a solid red with no voltage reading. Marathon has it in their dash light section of the handbook as a secondary charge system indicator.

[Archived]

Cal, isn’t your Marathon house and inverters 24v?

[Archived]

yes 24 volts.

cal

[DON]

Since you’re 24v house and chassis, aren’t both your alternators 24v?

[Archived]

Tom, both are 24V. I am beginning to think the system is a Marathon installed secondary charge system. The battery charge gauge on the dash reads 26v when the engine is running.

Cal

[David]

The reason I asked is you mentioned your 12v 50DN which should be 24v.

I’ve had 3 Marathons and the last two, a 2002 and 2004, with 4024 inverters displayed the house 24v on Techlink and the Prevost 24v was displayed on the dash Telltale. So I’m not clear on your comment about an secondary charge source. Your house is charged via the inverters or alternator and the chassis is charged with the second alternator. I assume you don’t have Prevost OTR.

The dash gauge at 26v is the chassis and it’s too low. That would be the small alternator with an internal regulator.

[Dick]

Its all about your signature when it comes to Marathon advice.

**

What Model?

What serial number coach?

and then what alternator did you replace, etc.. Picture of circuit may help you understand the circuit of a 2000 ish Marathon with a Delco 270A (House) and the typical 75 Amp Delco (Chassis). My bus not yours ….no other help available other then happy hunting.

[Archived]

Marathon mentioned the R terminal on the 50DN but didn’t let me know where that is. I plan to do some testing this morning. Any advice?

Cal

[Archived]

The R terminal is on the rear of the alternator on top of the flat part.

[joel]

We checked the large alternator this weekend and found the voltage coming out of the 24 volt stud on the 50dn at 100+ DC. The R terminal had 50+ volts. something does not seem right.

The voltage regulator had the following readings. FLD terminal 25.3 Bat. 26.1

and IGN 26.7. Engine was running at high idle.

Do we have a major issue with the alternator? Diodes gone bad?

Cal

---

1999 XLV X-6872,  liberty #440

[David]

I plan to replace the 50DN voltage regulator per Marathon. Not sure it is the problem but was only a 100 dollars. Marathon gave me cryptic answers so I thought I would start there. I don’t think they like spending much time with a customer in answering questions who is not in the market for a new coach.

The unit I am changing out is attached.

My question is where is the main disconnect for the batteries. There is a small toggle switch next to the fuse bank in the engine compartment that turns off the chassis electrical. but it does not turn off the electric to the voltage regulator. I can’t locate a switch that will turn off the electrical to the regulator. If no switch should remove the battery wire first on the regulator first to eliminate any power to short out the regulator? Let me know thoughts.

Cal

[Archived]

My last 2 H’s had a toggle switch in the small rear chassis battery bay curb side.

[Jeff]

Just installed a new rebuilt 50DN alternator today, the 24 voltage regulator was replaced 2 weeks ago.

Here is where I am at. On the new 50DN voltage on the 24 V stud is around 28 with the engine running at high idle. The 12 volt stud is about 14V. Here is where i need help. The batteries are not charging per the inverter readouts in the coach. The voltage reads 25.2 on both with the engine on high idle. . When the unit is hooked to shore power or the Gen is running voltage shows high 27 or 28.

Does any one have an idea what might be going on? BTW the dash light still remains on since it is not charging. Is there another electronic relay that is not functioning.

Thanks

Cal

[CHIP]

Are you measuring the voltage at the Equalizer?