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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 27635
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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key-off battery drain problem..runs down..truck wont..multimeter

Resolved Question:

Question for RON.

PROBLEM - I have a key-off battery drain problem that runs down the battery. Takes 1-2 days to drain the battery with the key off, so the truck won't start.

WHAT I'VE DONE ABOUT IT - First, I installed a knife switch on the positive terminal of the battery. Second, I performed troubleshooting with a multimeter. With a multimeter connected across the open knife switch, I pulled every fuse under the hood and inside the cab, one-by-one, until I found which circuit was draining the battery. The draining circuit was FUSE #14, 15A, "Battery Saver Relay, Interior Lamp Relay". I pulled FUSE #14 to prevent battery drains, but cannot fix the underlying problem.

MY QUESTIONS - How do I fix the battery drain problem with FUSE #14, "Battery Saver Relay, Interior Lamp Relay"? What is the "battery saver relay" and how is it supposed to work? Can you give me a circuit diagram so I can troubleshoot where the drainage is coming from?
Submitted: 3 years ago.
Category: Ford
Expert:  Ron replied 3 years ago.
Hello and Welcome to Justanswer,
My name is XXXXX XXXXX I am here to try and assist your with your question. Enclosed isa the battery saver relay discription and if you are sure there are no light coming on then it may be defective or even a GEM module problem. Which wire diagram do you need.

Battery Saver Relay

The following components are under the control of the battery saver relay:

Delayed accessory relay.

Overhead interior lamp with map lamps.

Underhood lamp switch.

Glove box lamp switch.

Overhead interior lamp switch.

Intior lamp coil.

The battery saver relay becomes active (relay coil is energized) when the GEM is in awake mode and is deactivated (relay coil is de-energized) in sleep mode.

The battery saver will remain active until the ignition state is not ACC or RUN and 45 minutes have passed since last active input. At that time, the relay will be deactivated and power to the above circuits will terminate.

Five minutes after the battery saver relay has become deactivated, the GEM will go into a lower power state known as sleep mode. In the sleep mode, the GEM will deactivate all outputs and will monitor select inputs.

Logical characteristics of the Gem battery saver mode are as follows:

Feature Inputs:

Sleep/Awake mode status.

Feature Outputs:

Battery saver relay control (Open circuit in sleep mode, grounded when awake).

Customer: replied 3 years ago.
Thanks, Ron.
I don't know what GEM is?
I would like to have a schematic wiring diagram of what's connected to FUSE #14.
Without a schematic wiring diagram, I cannot visualize what the description above means. In other words, without a wiring diagram, I have difficulty visualizing potential failure modes.

Where is the 45 minute timer? Is the timer inside the relay? Or in the GEM? Would a battery drain occur if the battery-saver relay failed? Or would a battery drain only occur if the relay failed AND a light were left on?

In your experience, what are the likely failure modes?

Thanks
Expert:  Ron replied 3 years ago.
The GEM is the Generic Electronic control module and it mounts to the top side of the interior fuse panel.



Central Timer Modules (CTMs) are equipped on two-wheel drive vehicles without power windows. All other vehicles have a Generic Electronic Module (GEM) .

NOTE: CTM diagnostics are not compatible with the New Generation STAR (NGS) Tester; instead, the diagnostics are internal to the module. The diagnostic mode is entered by shorting two pins of the diagnostic connector together.

The GEM inputs and outputs are designed to withstand continuous exposure to a short circuit to ground or battery voltage without being damaged.

GEM Diagnostics
The GEM diagnostics are accessible with the New Generation Star Tester and the Service Bay Diagnostic System (SBDS) . The GEM constantly monitors its subsystems for concerns. If a concern is found in one of the subsystems, the GEM will record the concern in the form of a Diagnostic Trouble Code (DTC) .

There are three areas of diagnostic information useful when diagnosing the GEM.
  • DTCs A record of past or present system problems.
  • PIDs - The present state of an input or output.
  • Active Commands Gives the ability to turn on GEM outputs without activating the inputs normally associated with the function.

Ignition Switch Positions
The position of the ignition switch is very important to proper GEM operation. Often times, erratic or unexpected operation can be traced to problems on these GEM inputs. The following is a brief description of five ignition switch positions.

When the ignition switch is in the RUN position, battery voltage should be present at the GEM/CTM RUN and RUN/ACC input terminals When the ignition switch is in the ACC position, battery voltage should be present at the GEM/CTM RUN/ACC input terminal only.

When the ignition switch is in the START position, battery voltage should be present at the GEM/CTM start/clutch depressed input. The 45 minute time is in part of the GEM module.

The GEM module does not have an OFF or LOCK Switch State input. The GEM will assume the OFF or LOCK position when there are no RUN, ACC, or START signals present.

GEM Features and Functions

Expert:  Ron replied 3 years ago.
Here are the diagrams for that complete circuit.

graphicgraphicgraphicgraphic
Customer: replied 3 years ago.
Ron, thanks for an explanation of GEM, but you did not address my other questions, repeated below ...

I would like to have a schematic wiring diagram of what's connected to FUSE #14.
Without a schematic wiring diagram, I cannot visualize what the description above means. In other words, without a wiring diagram, I have difficulty visualizing potential failure modes.

Where is the 45 minute timer? Is the timer inside the relay? Or in the GEM? Would a battery drain occur if the battery-saver relay failed? Or would a battery drain only occur if the relay failed AND a light were left on?

In your experience, what are the likely failure modes?
Customer: replied 3 years ago.
Okay, Ron, thanks for the schematic diagrams ... I believe they will help!

Can you address my other questions, repeated below ...

Where is the 45 minute timer? Is the timer inside the relay? Or in the GEM? Would a battery drain occur if the battery-saver relay failed? Or would a battery drain only occur if the relay failed AND a light were left on?

In your experience, what are the likely failure modes?
Expert:  Ron replied 3 years ago.
If you look above I have enclosed all 4 diagrams and the timer is part of the GEM module which times out the GEM and shuts all the light that come from the GEM and place the GEM in sleep mode. If its not the relay sticking then I would suspect the GEM has failed.
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 27635
Experience: 23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
Ron and 5 other Ford Specialists are ready to help you
Customer: replied 3 years ago.
Thanks, Ron. I think I have enough to INTELLIGENTLY troubleshoot the problem.

You da man.

Greatly appreciated.

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Ron
Ron
Automotive Tech
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23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs