12V Block Diagram & Diagnostics

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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]

http://manuals.heartlandowners.org/


http://manuals.heartlandowners.org/?man=User%20Guides

mailto:[email protected]




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






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.






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)

++

+





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.









KIB Control System Block Diagram mid-2020 Landmark 365





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






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.





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.





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.



12V Block Diagram & Diagnostics

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