12v block diagram & diagnostics
TRANSCRIPT
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12V Block Diagram & Diagnostics.pdf P a g e | 1 Version: 2, September 14, 2020
12V Block Diagram & Diagnostics
This guide is intended to assist Heartland Owners in understanding the operation of the 12V power
distribution system and to troubleshoot when multiple failures occur at the same time.
Important Notices
Who created this document?
This document has been created by Heartland Owners independently of the
Heartland RV Company, and is posted to the Heartland Owners Forum, by
owners, as a service to the entire owner community.
Errors and Omissions
Because the authors are Heartland owners, not engineers or service technicians,
it’s possible that this document could contain errors or omissions. Readers are
advised to also review the manufacturers’ product documentation for more
complete information and guidance.
Additional Resources
The heartlandowners.org website has a collection of owner-written user guides,
including information on water systems, heating and cooling, winterizing,
residential refrigerator, water heater and other topics. This information is
available at http://manuals.heartlandowners.org/?man=User%20Guides
Limitations on Using this Document
This document may not be modified or sold.
It may not be posted on the internet without permission.
Other websites may link to the page from which the document may be
downloaded, but may not link directly to the document without
permission (search engines excluded).
Contact Information
Questions and comments may be directed to [email protected]
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12V Block Diagram & Diagnostics
Table of Contents How to use this guide ................................................................................................................................... 3
Block Diagram of 12V System Components .................................................................................................. 4
KIB Control System Block Diagram mid-2020 Landmark 365 ................................................................... 6
12V Block Diagram for Residential Refrigerator ....................................................................................... 7
Failure of 12V Lights and other 12V Systems when Shore Power is Disconnected ...................................... 7
Troubleshooting Flow Chart – Start Page ..................................................................................................... 8
Troubleshooting Flowchart – Battery Diagnosis ........................................................................................... 9
Revision History .......................................................................................................................................... 10
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12V Block Diagram & Diagnostics
How to use this guide This guide is intended to assist Heartland Owners in understanding the 12V systems in their RVs, and to
help diagnose 12V failures where multiple devices stop working at the same time.
Please note that the goal of this document is to help in the majority of circumstances where multiple
12V devices are failing at the same time. It is not comprehensive in that there may be less common
causes of failure that are not included. Also note that diagnosis of failures affecting a single 12V device
are outside the scope of this document.
To use the guide, first review the Block Diagram and notes page. Then step through the Diagnostic
Pages to isolate the problem.
On the Diagnostic Pages, there are several shapes used. Diamonds indicate a question. Rectangles
indicate an action you need to take. Ovals represent a diagnosis or corrective repair action. There are
also shaded rectangles that provide background information.
It is assumed that you have a volt meter capable of reading AC and DC voltage levels. If you don’t have a
volt meter, follow the flow charts as much as possible. Certain problems can be identified without a
meter. For other problems, you will need a meter.
Additional information may be found in the Electrical User Guide and other owner-written materials.
.
CAUTION: Electricity is dangerous. Many of us are comfortable with checking
120V AC and 12V DC circuits and are confident we can do so without damaging
the circuits or causing injury to ourselves. If you’re are not comfortable around
electrical circuits, you should consider letting a trained technician diagnose
and correct the problem.
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Block Diagram of 12V System Components The block diagram below is a generic representation of how Heartland connects the key 12V DC
components. Heartland has used a number of variations over the years, so your actual configuration
may differ.
Note that the output of the Power Converter goes to the fuse box inside the trailer, and to the battery.
And the output of the battery goes to the fuse box inside the trailer. Power can flow in both directions.
Also note that the battery path goes through a 12V mini-circuit breaker that has a manual reset. If that
breaker ever trips, the battery will not get recharged and will not be able to supply power to the fuse
box for times where there is no shore power available.
Battery
Power
Converter
12 Volt
Fuse Panel
inside coach
supplies 12V
to lights, Frig,
& other 12V
appliances.
12V Circuit
Breakers
+
-
-
To Hydraulic
Pump,
Rear Stabilizer
Jacks,
Selected other
high current 12V
devices.
120V input thru
120V circuit breaker
panel
Power Converter supplies power
both to the 12V Fuse Panel and
to charge the battery.
12V
Bu
ss
Ba
r
Auto Reset
Circuit BreakersNote: some trailers
may have a different
mix of auto and
manual breakers.
Manual Reset
Circuit Breaker
(tiny button on
end)
++
+
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When plugged into shore power, 120V is supplied to the main AC circuit
breaker panel inside the RV. One of those circuit breakers supplies power
to an outlet, usually found behind the basement wall, into which the Power
Converter is plugged.
The Power Converter converts 120V AC into 12V DC power to both charge
the battery, and to supply power directly to the 12V main Fuse Panel inside
the RV.
In order to charge the battery, the output of the Power converter goes
through one of the 12V automotive style circuit breakers located on a buss
bar near the battery.
The other 12V Circuit Breakers supply power to high current devices like the
Hydraulic Pump, Rear Stabilizer Jacks, Power Cord Reel, and electric slide-
outs.
Intermittent tripping of the auto-reset circuit breakers, especially the one for
the Hydraulic Pump, may indicate a weak breaker that needs to be replaced. For more information on
this type of failure, see our owner-written Hydraulic Slide Starts and Stops guide. The information in that
guide applies mainly to hydraulic slides and hydraulic landing gear, but may also be helpful with the same
symptoms on electric motor levelup systems.
12V DC configurations vary quite a bit. For example, on late 2020 and 2021 Landmark 365s, much of the
12V power is routed through a set of KIB Control Boards, allowing operation via a touchscreen tablet or a
phone app. More information on this configuration may be found in the Landmark 365 User Guide V30
Mid 2020 and in the KIB Multi-Plex Control System V2 guide.
12V Circuit
Breakers near
the battery.
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KIB Control System Block Diagram mid-2020 Landmark 365
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12V Block Diagram for Residential Refrigerator Units with a Residential Refrigerator (120V AC only) employ yet another 12V DC layout as shown below.
More information may be found in the Residential Refrigerator guide.
Failure of 12V Lights and other 12V Systems when Shore Power is
Disconnected
If the 12V lights and other 12V systems lose battery power after disconnecting from shore power, it’s
often because the Manual Reset Circuit Breaker on the buss bar near the battery has tripped. If this
circuit breaker trips, the battery no longer gets any charge from the power converter and will run down,
causing failure of 12V systems. When plugged into shore power, the battery charging problem Is
masked because 12V power is also supplied by the Power Converter.
Power
Inverter
Converts 12V
DC to 110V AC
Battery
Cutoff
Switches
Transfer Switch Power to Refrigerator
Powered from
outlet usually
located
behind the
basement
wall.
Power
Converter
Converts
110V AC to
12V DC
110V AC
Grounded
Outlet behind
refrigerator
22 Cu Foot
Residential
Refrigerator
(110V only)
Shore Power 110V AC
Input To Transfer Switch
Inverter (battery) 110V AC
input to Transfer Switch
110V Circuit
Breaker Panel
inside coach
(breaker positions
vary)
12V DC to high current
devices: Hydraulics
Pump, Electric Slide
Motors, etc. (breaker
positions vary)
12 Volt Fuse Boxinside coach.
Powers lights and 12V
circuit boards in appliances
Block Diagram of Residential Refrigerator Electrical Wiring 4/23/2014
Note: Transfer switch
defaults to inverter
(battery) power when no
shore power is present.
Remote Switch
Momentary Remote Switch on control panel inside
coach or inside front storage compartment turns Power
Inverter ON or OFF. When OFF, pressing once turns
unit ON. When ON, pressing once turns unit OFF.
When 12V DC power is first applied to the Inverter, you
will need to press the Local or Remote power switch to
ON before AC power will be generated.
Light at remote switch indicates Power Inverter is ON
Batteries Wired in Parallel
for 12 Volt Output to run
Coach & inverter
12V Buss Bar &
Mini Circuit Breakers
12V Buss Bar &
Mini Circuit Breakers
12V To Breakaway Switch & from
Tow Vehicle Power (always hot)
Converter output
And battery output
Teed together so
Both supply 12V
DC to Fuse box
GFCI outlet with reset button. (Inverter must be ON
and have battery power for reset button to operate.)
100 Amp 12VC Fuse
++-
12 Volt
Battery
++-
12 Volt
Battery z
NOTE: A few early Residential Refrigerator
shipments do not have a Cutoff Switch in
the path to the Power Inverter. To prevent
parasitic drain on the battery while in
storage, you must use the Power Inverter
power switch to turn the unit OFF.
To Battery Cutoff
To Generator Start (always hot)
Frame
Ground
Transfer Switch
Inputs: shore
power and inverter
(battery) power.
Output: to
refrigerator
12V DC to and from battery
50 Amp 12V DC Manual
Reset Circuit Breaker
Local Power Switch on
Inverter is a convex domed
“blister” type ON/OFF
switch
12V DC to/from Power
Converter & to Fuse Box
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Troubleshooting Flow Chart – Start Page
For use when multiple 12V appliances and devices are failing.
/
Everything
OK On Shore
Power?YES
START
HERE
If OK on shore power,
Power Converter is working
Do
interior 12V
Lights
work?
Press tiny RESET
Button on manual
reset 12V circuit
breaker on buss
bar (see diagram)
NO
Restore power to
Converter. If
unplugged, secure
plug to outlet.
Check Power
Converter 110V
circuit breaker.
Check plug at
outlet in basement
110 V to
Power
Converter?
Power
Conv internal
Fuses OK?
Make sure battery
Is connected correctly
& replace converter
fuses.
12V at output
Power Conv?
May need new
Power Converter.
Temporarily use battery
charger to keep battery
charged.
NO
YES YES
NO NO
Press tiny RESET
Button on manual
reset 12V circuit
breaker on buss
bar (see diagram).
NO
Suspected
problem with
Power
Converter.
Battery may
have run
down as a
result.
Check 12V connections
at converter and buss
bar (see diagram).
YES
110v
Appliances
also
Failing?
NO
110V problem. Check
pedestal, main plug to RV,
main circuit breakers in
RV, Transfer Switch.
YES
Do
slides or
Landing jacks
Work?
YES
NO
Problem
Resolved?
High-current
devices require
a good battery
charge to
operateHas battery
Been
discharged?
NO
Charge Battery
YES
To Battery
Diagnostic
Page
NO
Problem
Resolved?
NO
12V systems
seem OK.
Troubleshoot
failing device
YES
BATTERY CUTOFF MUST BE ON, SHORE POWER CONNECTED.
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Troubleshooting Flowchart – Battery Diagnosis
Battery
terminals &
Cables OK?
Clean terminals,
tighten or replace
Cables.
NO
Fill as necessary
Batt water
Level OK
All cells?
NO
May need new
battery.
Get battery tested
professionally
YES
High-current
Systems require a
Good battery
Charge to
operate
From Start
Page
Turn off 110V circuit
breaker for Power
Converter to test
battery.
YES
Minimum
Of 12V at
buss bar near
battery?
Operate slide or
landing jack while
measuring Neg Batt
Terminal to frame
ground.
Voltmeter reads
> 0 V DC?
Check battery neg
terminal ground
Possible grounding
problem on
failing devices
YESNO
YES
NO
Voltage on battery
negative terminal
indicates poor
grounding.
Has battery
been
discharged?
NO
Charge battery via
Power Converter or
external charger and
restart diagnostics.
YES
Isolate battery from
Power Converter
before checking
battery condition.
Remember to flip
circuit breaker for
Power Converter back
to ON position.
If battery looks ok,
But doesn’t deliver
Enough power,
Test for grounding
Problems.
BATTERY CUTOFF MUST BE ON, SHORE POWER CONNECTED.
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Revision History
February 28, 2013 Version 1 Released
September 14, 2020 Version 2 Released with additional block diagram examples for
Landmark 365 and Residential Refrigerator installations.