need dc troubleshooting help

[garrison]

1998 Itaska Suncruiser. I am finding that my new "House" battery discharges rapidly without the aid of the engine's alternator, generator or shore power. In other words the Converter is doing it's job and produces 12.5v under load and as per the manufacturer's guidelines about 14 volts when all load is removed. I have found the front air conditioner will not run with the converter plugged into it's 115 vac recepticle but runs fine when I unplug the converter. I suspect that there is a short somewhere, dropping the converter's dc output to something below what the air conditioning dc circuits need to start it. I have pulled each wire off the dc panel's circuit breakers while checking for a voltage increase on the output of the converter but found no changes. I also pulled the auto circuit breakers one by one for the steps, radio, etc. I haven't disconnected the heater or the water heater circuits though since they were not in use. Has anyone had this problem in the past? I would appreciate any further troubleshooting ideas. Thanks so much in advance...

[Paul R. Haller]

How many watts is your inverter rated to? If it can not produce the amps needed to run the AC, maybe it drops voltage to protect the output transistors. Check output amps for your inverter.
-Paul R. Haller-

[RickO]

Hi and welcome to the forum.

Is this a coach you've had for a while and these are new symptoms, or have you recently obtained it and are trying to make things work for the first time?

So, is this the problem you're trying to solve?

"I am finding that my new "House" battery discharges rapidly without the aid of the engine's alternator, generator or shore power."

And you say:

"In other words the Converter is doing it's job and produces 12.5v under load and as per the manufacturer's guidelines about 14 volts when all load is removed"

So you have a converter rather than an inverter/charger?

"I have found the front air conditioner will not run with the converter plugged into it's 115 vac recepticle but runs fine when I unplug the converter. I suspect that there is a short somewhere, dropping the converter's dc output to something below what the air conditioning dc circuits need to start it."

Do you mean that your AC works when you unplug your converter but leave the coach attached to shore power?

Rick

[RickO]

Originally Posted by Paul R. Haller

How many watts is your inverter rated to? If it can not produce the amps needed to run the AC, maybe it drops voltage to protect the output transistors. Check output amps for your inverter.
-Paul R. Haller-

I was wondering the same thing but he doesn't indicate whether he's even got an inverter/charger or just a converter. I doubt that the AC units would even be wired to allow them to run off of an inverter.

Rick

[garrison]

The converter, I assume you meant, is a Magnetek model 7445 rated at 45 amps. It is OEM installed and has been in the MH since new I presume. But something electrical has changed, (short, etc.). I was thinking of adding a ammeter between the positive battery terminal and the Positive main (red) terminal wire to see if there is any discharge when everything is turned off to find the amperage drain. Good idea, thanks Paul

[Clay L]

The 7445 converter output should be about 13.5 volts under normal loads not 12.5.
!2.5 volts is about what a charged battery should read (12.6 + is fully charged). In any case it should be enough to operate the AC control board.

[garym114]

Primary job of the converter is to supply DC to the RV when plugged in. Yours is failing in that respect if it is not providing the voltage necessary to operate the AC thermostat.
Charging the battery is secondary.

[FIRE UP]

As usual gang,
I'm always learning things on these sites. I was always under the impression that a "Converter", which, is normally supplied with a gas coach, only "converts" A/C to D/C so that all the D/C powered components on the coach will operate normally without draining the coach house battery. And that, the Converter has NOTHING to do with the operation of any air conditioner since they are only 110 A/C, correct?

So, as one says, there is apparently some 12V needed at least to operate the thermostat portion of the A/C operation, correct? And, if that's the case, then is that thermostat different than a residential thermostat, which, I presumed operates on some sort of low voltage due to the small wires running to it?
Scott

[RickO]

Originally Posted by FIRE UP

As usual gang,
I'm always learning things on these sites. I was always under the impression that a "Converter", which, is normally supplied with a gas coach, only "converts" A/C to D/C so that all the D/C powered components on the coach will operate normally without draining the coach house battery. And that, the Converter has NOTHING to do with the operation of any air conditioner since they are only 110 A/C, correct?

So, as one says, there is apparently some 12V needed at least to operate the thermostat portion of the A/C operation, correct? And, if that's the case, then is that thermostat different than a residential thermostat, which, I presumed operates on some sort of low voltage due to the small wires running to it?
Scott

12VDC is required to operate the control boards on many 120VAC appliances.

rick

[garrison]

Sorry this is so long folks but it may help someone else out there. Ricko, I 've only had the RV for a coupla months so these issues are new to me. to review, the "house" battery was discharging when everything was "static", ie, not on shore or genny power. Also I found the front air conditioner would not run with the converter plugged in, (not the inverter which is not in the picture here). And yes, the converter is a rectifier/charger combo. Here's what I found: I put an ammeter between the terminal of the house battery and it's battery cable and immediately measured almost an amp of "drainage from the house battery when everything was "static", ie lights, fans, etc all off and the RV was NOT being powered by shore power or the generator. Powering everything up again, I then, in sequence, unplugged each dc wire on the dc circuit breaker panel. I found the "drain" dropped immediately to an acceptable 0.2 amps when I unplugged the "monitor/TV" wire. Low and behold, the output of the Converter's voltage jumped to the normal of 13.5 volts.(as Clay L so kindly added). AND the front air conditioner now works as advertised.
So, problem solved..except for finding the excess current drain in the Monitor/TV circuits.
This is important...the the original 12.5 volts I read on the output of the converter , under load, was was due to excess current drain through the monitor/tv circuit. This makes sense since P=I x E or as current increases, voltage drops to maintain the rated Power that the converter provides. As GaryM114 suggested, the converter's voltage drop would suggest that it is faulty but in this case, it's just fine now without that extra current drain that I now must isolate.
by the way, the monitor/TV circuits include the water pump, water heater and "levels" switches. The levels test switch lights up the holding tanks 1 and 2, the fresh water level, the lp gas level and the battery condition (and of course the TV Video control center which I eliminated earlier.
So, here I go. I'll try to isolate each one of these sub-circuits until I find the culprit. I suspect that it may be found in a water pump or a faulty "levels" probe. Wish me luck. Hope this helps someone else out there!

[Dave78Chief]

Did not see this thread until after I responded to your e-mail. You are on the right track. As shown on pdf page 20 of http://www.winnebagoind.com/diagram/1998/126141.pdf this is circuit JA. For some reason they did not show a connection to that circuit breaker on pdf page 3 of http://www.winnebagoind.com/diagram/1998/126583.pdf. But the excessive load is on circuit JA of that drawing.

Dave

[garrison]

Originally Posted by Dave78Chief

Did not see this thread until after I responded to your e-mail. You are on the right track. As shown on pdf page 20 of http://www.winnebagoind.com/diagram/1998/126141.pdf this is circuit JA. For some reason they did not show a connection to that circuit breaker on pdf page 3 of http://www.winnebagoind.com/diagram/1998/126583.pdf. But the excessive load is on circuit JA of that drawing.

Dave

Thanks for the help so far and the new resources of the schematics. Didn't have those before. Yes, Unplugging the circuit JA (Monitor/TV) with 110VAC powering the coach (house) I get a voltage increase at the converter to an acceptable 13.5 VDC. I have to unplug the wire Monitor/TV because it has push to reset type CBs. So, the problem is finding what circuits are on that wire besides the monitor (which I assume means the panel to check the battery condition, levels and has the water pump and water heater switch).

[wa8yxm]

A thought comes to me.. To follow up on this thought I need to be 100% sure I have the proper converter so I can check it's manual.. However since you should have the manual in your owner's manual bag I will tell you what to check for.

There are two types of converters for this discussion, (There are more but not for this discussion) one type is like the Progressive Dynamics 9200 series, Two wires on the DC side, one negative One positive.

The other type is like the converter module in the Magnetek 6300, THREE connections on the DC side, one negative and TWO positive, one blue.

The 74xx series designation suggests it is a Parallex, Parallex bought out Magnetek, I do not, however know how the 7400's are wired I do know they are better than the 6300's.. (Downloaded the manual, appears they are not like the 6300)

That assumes you actually do have a parallex 7400 series.

The 6300, if you were on shore power your lights and things like thermostats ran off the CONVERTER, not the battery

The 7400 the converter and battery are in parallel.. HOWEVER there is one more issue

There are two types of thermostats, Electronic and mechenical.

Now a mechenical T-Stat does not care if it's eating AC, DC or a combination of the two.

But an electrionc one does.

My Progressive Dynamics converter outputs nice clean DC, but some (The Magnetek did this) output rectified ac.. I will explain the waveform like this....

Take some tracing paper, Draw a straight line, Now draw a sine wave on top of the line

Now fold the paper on the straight line.. What you now see is rectified (Full wave) AC.

AN electronic T-Stat may object to this..

NORMALLY the battery acts like one humungous filter to smooth that out but .. IF the battery is either.

1: Bad (Failure mode high resistance) or 2: poorly connected (See high resesistance)

It can not filter.

[Dave78Chief]

Several items use the JA circuit
Front and rear TV sound ampifiers
Power source for monitor panel (tank levels, water pump, water heater)
Range Hood
Galley Overhead lamp
Entertainment Center

You are going to have to disconnect plugs and turn off switches to isolate the problem device.

Dave

Dave