Voltage Readings 1997 U 320 M-11

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Voltage Readings 1997 U 320 M-11

July 28, 2012, 11:11:55 pm

Hi All,
My dash monitor has started to show 14.8 to 14.9 volts when running down the road. It has never been this high. The dash gauge still shows about 13.5. I put the meter on the batteries, at high idle, it reads 13.85.
Batteries read 12.8 first thing in the morning, no engine running. Any ideas what may be happening? Anything else I should be checking?
Thanks,
Raymond
1997 U 320

Re: Voltage Readings 1997 U 320 M-11

Reply #1 – July 28, 2012, 11:21:50 pm

check the voltage on at the back of the alternator, see if it is bouncing

Re: Voltage Readings 1997 U 320 M-11

Reply #2 – July 29, 2012, 12:32:30 am

Raymond,
Some thoughts;
Dash meter shows engine battery, downstream of the isolator. 13.50 Vdc (given)
Engine Batteries at high Idle (by voltmeter) 13.85 Vdc (given, reasonable)
Dash monitor (Javelina) shows house battery, downstream of the isolator. 14.80 to 14.90 Vdc (given, not reasonable)
Do house batteries at high idle show (by voltmeter) 14.80 to 14.90 Vdc?
If so, No, No for Gels or AGM's..........MUST FIX!
Does Alternator output at high idle show (by voltmeter) 15.50 to 15.70Vdc?
If so, a high resistance connection in the engine battery loop may be causing the alternator to run at too high an output voltage because a volt is being dropped somewhere across a high resistance connection in the engine batteries circuit. That can be in the battery isolator diode for the engine batteries, in the positive or in the negative engine battery leads or at either the positive or negative engine battery terminals. Are the voltage drops across the two battery isolator diodes essentially equal and about 0.75 to 0.90 Vdc each? Are the engine battery negative terminals each 0.00 Vdc with respect to coach frame?

At high idle, from the engine battery isolator diode output terminal, first check each successive engine battery circuit wire termination voltage to ground (coach frame) and second to each negative engine battery terminal post and see if you can't find where the voltage reading drops a volt with respect to the isolator output voltage.
FWIW,
Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #3 – July 29, 2012, 06:16:05 am

Agree with Neal, you need a reliable DC Volt meter (VOM, VTVM or what ever works) to be able to read and locate any issues. Some times it is less trouble to take to a shop that understands what your talking about AND can repair it.
One of my learning experiences, it to find the correct shop for what you need.
For me, MOT, FOT, Xtreme are the best at what they do, anywhere else is a crap shoot.
MO
Dave M

Re: Voltage Readings 1997 U 320 M-11

Reply #4 – July 29, 2012, 08:47:16 am

You should check the voltage sense wire that runs from one of the outside isolator terminals to one of the small terminals on the back of your alternator. If it's not clean/tight/good contact it can make your alternator drive high. Many but not all of the Leece Neville alternators have an adjustable regulator also with a small bus bar you shift between terms after removing cover. Default setting is high.

Re: Voltage Readings 1997 U 320 M-11

Reply #5 – July 29, 2012, 12:00:06 pm

Raymond,
Dave M is exactly correct in that you need to be using a digital VOM/VTVM/or similar that gives you a reliable, repeatable two or three digit readout (precision/accuracy not as important; +/- 5% of full scale readout is fine).
I'm not sure how much troubleshooting of this problem you feel comfortable doing yourself.
The early Unicoaches, like yours and mine, (actually '95 thru 2000 I believe, U270,295 and 320's alike) had a quirk associated with the "Remote Sense Alternator Location". If yours has not been modified from the original wiring configuration, you should read the following:
http://www.foreforums.com/index.php?action=media;sa=item;in=918
I posted that about 5 years ago and I know that the information has helped a number of owners with "Alternator Remote Sense Wire Issues".
I could be wrong, but I don't believe that yours is a remote sense issue because if it were, both of your battery banks would be showing higher than normal voltages.
If I understand your information correctly, I believe it is more likely to be a high resistance connection that is dropping voltage (somewhere in the engine battery wiring circuit) or a battery isolator diode problem (greater than 0.75 to 0.90 Vdc on the engine battery side or [partially or fully] shorted [near 0.00 Vdc] on the house battery side).
FWIW,
Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #6 – August 19, 2012, 12:59:00 am

Hi All,
Does anyone know what brand/type/model isolator I should be using with my 1997 U320?
Thanks,
Raymond

Re: Voltage Readings 1997 U 320 M-11

Reply #7 – August 19, 2012, 01:51:38 am

You need a standard three pole isolator. It should be rated at least 200 amps maybe more depending on your alternator.

Re: Voltage Readings 1997 U 320 M-11

Reply #8 – August 19, 2012, 11:13:12 am

Hi All,
The Cole Hersee 48160 200 amp isolator is a three pole. It says it's for an alternator without an internal voltage regulator. They have a 200 amp 48162. Any ideas which to use?
Thanks again,
Raymond

Re: Voltage Readings 1997 U 320 M-11

Reply #9 – August 19, 2012, 04:53:35 pm

Have you been able to prove that your isolator is bad?

Re: Voltage Readings 1997 U 320 M-11

Reply #10 – August 19, 2012, 09:15:53 pm

Hi John,
It may still work. But the material that it is made of is falling apart. The stud where the engine start batteries connect has melted material coming out next to it. It appears as a crack, where material has melted out. The material has hardened, but the stud is not solid like the other two. I have not been able to do any testing today. So I think I may need a new isolator.
Raymond

Re: Voltage Readings 1997 U 320 M-11

Reply #11 – August 30, 2012, 08:57:36 pm

Hi Neal,
Here is my 1997 U 320 electrical schematic. Could you show me where I should modify it for the "remote sense alternator location" modification.
Thanks,
Raymond

Re: Voltage Readings 1997 U 320 M-11

Reply #12 – August 31, 2012, 12:03:36 am

Quote from: Raymond Jordan – August 30, 2012, 08:57:36 pm

Hi Neal,
Here is my 1997 U 320 electrical schematic. Could you show me where I should modify it for the "remote sense alternator location" modification.
Thanks,
Raymond

Raymond,
On your isolator board (the board that your isolator is mounted to) on the forward bulkhead of your engine compartment, you have a 15A Bosch relay that should have three wires (E59 WH, E85 WH, and B33 WH) landed on one side of the relay and one wire on the other side (B35 WH).

If it were my coach,

I would take the Alternator Voltage Sense wire (E59 WH) off of that Bosch relay, I would add an inline (15A) circuit breaker that I would buy from NAPA, Auto Zone or the like, and I would extend that E59 WH wire (14 gauge, twisted strand) on, in a split loom protector cover, down to one of the (+) terminals of your engine start batteries. The goal is to get the alternator sense wire to as "true" a location as possible with respect to actual start battery positive terminal voltage. "True" meaning that there is the lowest probability of a poor (high resistance) connection providing a false, low voltage, back to the alternator. A false, low "sensed" voltage will cause the alternator to try to put out more voltage than is appropriate, thus "cooking" your house and start batteries with a voltage that is too high (greater than 14.0 - 14.1 Vdc at the (+) terminals for Gel and AGM batteries).
The boost solenoid is also on your Isolator board and the B5 000 wire is a large gauge wire that makes the "E" terminal of the boost solenoid a 2nd possible location to land the E59 WH extension wire. I would only use that 2nd option if you absolutely cannot figure out a way to land the (extended E59 WH) wire on one of the start battery (+) terminals and you don't want to take it to a repair shop to have it done. Likewise the B14 2RD wire junction point on your new Isolator (3rd, and even less desired option for relocation of the sense point).
The first option is the one to stick with, if at all possible!
Hope this is of help.
Call if any questions.
Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #13 – August 31, 2012, 12:55:55 am

Neals advice is right on!

I have a thread running, ALTERNATOR REBUILD, I'm trying to address about the same problem you have.

I did what Neal advised, I had no out put from my new alternator. I ran the DUVAC wire from the remote start panel to the alternator DUVAC (sense) terminal but still did not have any alternator output. When I checked it was slightly less than 12v.

I ran a wire directly from the + post of the start battery bank(3) to the DUVAC terminal on the alternator. I now have about 15.25V at the alternator and around 14.25 at the isolator. I have yet to add the fuse Neal suggests, I will do that Friday, It wasn't till I read your post and Neals suggestion that I saw the correct fuse to install in the line.

Re: Voltage Readings 1997 U 320 M-11

Reply #14 – August 31, 2012, 02:28:15 am

We ran a wire from alternator voltage sense terminal directly to start battery through a fuse.

Since we had to run wire from street side to curb side, I ran the wire through a small diameter PVC pipe, cable tied to frame members to keep wire from sagging and keep it protected.

Re: Voltage Readings 1997 U 320 M-11

Reply #15 – August 31, 2012, 08:34:01 am

Quote from: Lon and Cheryl – August 31, 2012, 12:55:55 am

Neals advice is right on!

I have a thread running, ALTERNATOR REBUILD, I'm trying to address about the same problem you have.

I did what Neal advised, I had no out put from my new alternator. I ran the DUVAC wire from the remote start panel to the alternator DUVAC (sense) terminal but still did not have any alternator output. When I checked it was slightly less than 12v.

That is quite a voltage drop-- below 12 VDC at remote start with engine running. I would start testing/cleaning connections until that significant drop is substantially reduced.

Re: Voltage Readings 1997 U 320 M-11

Reply #16 – August 31, 2012, 12:38:33 pm

Quote from: wolfe10 – August 31, 2012, 08:34:01 am

That is quite a voltage drop-- below 12 VDC at remote start with engine running. I would start testing/cleaning connections until that significant drop is substantially reduced.

Brett,
I have had poor experience with our dash A/C system holding a charge and the A/C Compressor clutch burning out. FT has worked on it numerous times (six or more) and I've had Carrier, Featherlite and Parliment all work on it as well.......dyes and black lights from start to finish several times................before finally abandoning the system in place.
When I was trying to keep the system in service, I had to replace the compressor and the Bosch circuit breaker on at least four occasions. The 15A Bosch circuit breaker contacts are where I've generally found the voltage drop to be and, of course, the circuit breaker has to be replaced to clear the problem. I have not figured out why that CB fails, but I suspect one or more of the following (hostile heat environment, too much current through contacts, frequent (opening) operation under high current draw).
All this to say, a likely suspect for 12 Vdc (or less) at the Remote Start Panel may be a 15A Bosch relay contacts voltage drop, which will only be cleared by replacing the relay.
FWIW,
Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #17 – August 31, 2012, 05:11:40 pm

Hi Neal,
Here's my modified schematic. Is this how it should be?
Thanks for your help,
Raymond

Re: Voltage Readings 1997 U 320 M-11

Reply #18 – August 31, 2012, 05:13:49 pm

Quote from: Neal Pillsbury – August 31, 2012, 12:38:33 pm

Brett,
I have had poor experience with our dash A/C system holding a charge and the A/C Compressor clutch burning out. FT has worked on it numerous times (six or more) and I've had Carrier, Featherlite and Parliment all work on it as well.......dyes and black lights from start to finish several times................before finally abandoning the system in place.
When I was trying to keep the system in service, I had to replace the compressor and the Bosch circuit breaker on at least four occasions. The 15A Bosch circuit breaker contacts are where I've generally found the voltage drop to be and, of course, the circuit breaker has to be replaced to clear the problem. I have not figured out why that CB fails, but I suspect one or more of the following (hostile heat environment, too much current through contacts, frequent (opening) operation under high current draw).
All this to say, a likely suspect for 12 Vdc (or less) at the Remote Start Panel may be a 15A Bosch relay contacts voltage drop, which will only be cleared by replacing the relay.
FWIW,
Neal

Neal, where is the CB located? I will check that.
My remote start does not work, never bothered me as there is too much other stuff to get to for now. I replaced the toggle on/off switch and should replace the start button. You are correct about a hostile environment, all the connections on the back of that panel are poor condition.
I was receiving 11.9v at the back of the panel at the start button with ignition switch on.

Re: Voltage Readings 1997 U 320 M-11

Reply #19 – August 31, 2012, 09:37:36 pm

Quote from: Raymond Jordan – August 31, 2012, 05:11:40 pm

Hi Neal,
Here's my modified schematic. Is this how it should be?
Thanks for your help,
Raymond

That's correct Raymond.
If you go ahead with the change, let us know your results.
Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #20 – August 31, 2012, 10:22:30 pm

Quote from: Lon and Cheryl – August 31, 2012, 05:13:49 pm

Neal, where is the CB located? I will check that................................

Lon,
I'm not sure for 1995 builds. I would need a copy of your wiring diagram to know for certain.
BTW, the physical layout of the components on the "Isolator Board" is the same as the physical layout on the automotive wiring diagram (a handy thing to know).
If the 1995 layout is like the 1997's, the 15A Bosch circuit breaker will be mounted on the same metal mounting panel that the battery isolator is mounted on , in the engine compartment, on the forward bulkhead. The CB should physically be in the lower left hand (street side) corner of the metal "Isolator Board". To be certain, one has to look for the wire numbers, on the wires landed on the Bosch CB, that correspond with your automotive wiring diagram.
I think that 1995, 6 and 7 Unicoaches may have all been of the forward bulkhead configuration. In 1998, the Unicoach panel name was changed to "Relay Board", the 15A CB stayed on the "Relay Board", but the Battery Isolator and Boost Solenoid were moved to the curb side, rearmost compartment adjacent to the engine start batteries and the retarder accumulator cylinder. I believe that continued through at least model year 2000.
Do you have your wiring diagrams? If not, you can get them from FOT. Just a phone call away. That's one of the most valuable assets of a FT. Many SOB's don't know how a coach is wired on the very day that it leaves the factory (undocumented changes and unserialized revisions throughout any given model year). With FT's, once the Unihomes and Unicoaches started, FOT has traceability on a coach by coach basis. Maybe even before. I haven't thought to ask that question.
FWIW,
Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #21 – September 01, 2012, 02:26:34 am

Hi Neal,
Which type of circuit breaker should I use. Here are the choices. They are by Cooper Bussman

Type 2 modified reset thermal non-cycling circuit breaker requires the power source to be removed from the breaker before the breaker resets. Ideal for the RV industry. meets RVIA and S.A.E. J553 specifications. Hardware included. Available in 10 amp, 15 amp, 20 amp, 30 amp, 40 amp, and 50 amp capacities.

Or Type 3 manual reset thermal circuit breaker. A plastic housing makes these circuit breakers ideal for marine and recreational vehicle applications. Meets RVIA and S.A.E. J553 specifications. 12 and 24 volt DC. Hardware included. Available in 10 amp, 15 amp, 20 amp, 30 amp, 40 amp, and 50 amp capacities.

One is modified reset, other is manual reset. I do not know which is correct for my use.

Thanks again,
Raymond

Re: Voltage Readings 1997 U 320 M-11

Reply #22 – September 01, 2012, 06:21:35 am

Thanks Neal,
I found the CB exactly where you said, mounted on the isolator strip.
It was buried under the cables on the far left corner.
They look VERY corroded and I can see that a replacement should be made, even if they are still performing now.

As others have stated, NOT a good place to mount electronics especially with all the enclosed areas on the coach that these electronics could have been located.

I look forward to your advice on the question about what CB to replace with.

Re: Voltage Readings 1997 U 320 M-11

Reply #23 – September 01, 2012, 06:12:49 pm

Raymond, Lon,
I used a Type I CB that I got at either Auto Zone or Advance Auto. 15 Amp CB (CBC-15, Type I, 10-32 Stud-Mount Copper Bussman circuit breaker). I think that Barry mentioned that 5A would probably be more than needed (and if it bothers change upward to a 10 A rating) because the sense circuit is a low current draw. I just stayed with the original circuit (15A) design. After installing the CBC-15 inline, I used heat shrink tubing to insulate the studs after I connected the terminals to the E59 WH wire and the wire extension.

Type I Automatic Reset Circuit breakers automatically reset after opening. If the fault still exists, the breaker will continue to cycle between ON and OFF positions until the overload is corrected. These devices are sometimes called "cycling breakers." Type I/Automatic Reset circuit breakers do not address, or correct, overcurrent or fault conditions. They only react by cycling OFF and ON. Any overcurrent or fault condition that causes a Type I circuit breaker to operate must be corrected as soon as possible.

The reason that I didn't use a Type II or III CB is because when the "sense" wire opens (circuit breaker trips on fault and there is no auto reset), the alternator thinks that "sensed" battery voltage is low (0.0 Vdc) and the alternator trys to compensate by going to it's maximum output (high 15's to low 16's Vdc). If I didn't notice that condition for quite some time while driving, I could damage all of my batteries as there is no overvoltage alarm. On the other hand, with an automatic reset circuit breaker, my voltage should be spiking up when the CB opens on fault and then falling down when the CB automatically closes after the thermal trip element cools down to the reset point. Therefore I should have a better chance of quickly noticing the erratic behavior and being able to respond to the abnormality before I damaged any batteries.
The type III CB (manual reset) would be my second choice. If it trips on fault, the alternator would spike to its maximum output and the battery voltages would gradually climb. That would continue until you noticed the abnormally high battery voltages. Once the sense line overcurrent fault condition is fixed, you can manually reset the CB and continue to use its overcurrent protection.
Hope this helps, guys,

Neal

Re: Voltage Readings 1997 U 320 M-11

Reply #24 – September 01, 2012, 06:21:20 pm

Thanks for your sharing your knowledge Neal!

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