Battery positive contactor stuck closed

[Focus_pilot]

I drove the car pretty hard today and when I got home to charge, I received a charging fault. When I went to turn the car on, I received the stop safely now. I check the codes and it shows Battery Contactor A stuck closed, P0AA1 and P0A95 High voltage fuse A. Anybody seen this before?

 

[triangles]

Hope you are under warranty still. Ford doesn't do component level repair on the battery. They will only replace the whole battery pack.

If you are handy and competent to work on high voltage systems (ie won't electrocute yourself), you could probably put a new contactor in assuming you can find one.

Let us know how you resolve this.

Also if you haven't already, pull the safety disconnect plug behind the rear seat to power down the car. Otherwise you may kill the battery by running it too low since it cannot turn off and you cannot charge it.

 

[Focus_pilot]

Mine is a 2018 FFE, 35k on the mileage. I planned to have it towed to the dealer and see what happens. I am hoping it’s just a fuse.

 

[Heima]

The Service Manual says this for the P0AA1:
P0AA1:00 Hybrid/EV Battery Positive Contactor Circuit Stuck Closed: No Sub Type Information A fault is indicated when the BECM is first powered ON or commanding the contactors to open and internal high voltage battery measurements indicate the positive contactor is closed while the BECM is commanding the positive contactor open. When this fault is present, the vehicle does not start, the high voltage battery does not charge and the stop safely hazard (red triangle) warning indicator is illuminated in the IPC . If this fault is cleared or repaired while the ignition is ON, the ignition must be cycled from ON to OFF and back to ON before the BECM commands the contactors to close again.

E5 CONFIRM THE HIGH VOLTAGE BATTERY FAULT
Ignition OFF.
Inspect Upper High Voltage Battery Pack C4805E and Lower High Voltage Battery Pack C4804E for:
pushed-out, loose or spread terminals and loose or frayed wire connections at terminals - install new pins or repair wires as necessary
any damaged, pinched, cut or pierced wires - repair wires
damaged or bent pins - install new terminals/pins
corrosion (install new connectors or terminals - clean module pins)
Repair any concerns found.
Connect Upper High Voltage Battery Pack C4805E .
Connect Lower High Voltage Battery Pack C4804E .
Ignition ON.
Enter the following diagnostic mode: Clear Diagnostic Trouble Codes (DTCs) - BECM .
Ignition OFF.
Ignition ON.
Enter the following diagnostic mode: Self Test - BECM .

Was the original DTC retrieved on-demand during the self test?

Yes CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a Technical Service Bulletin (TSB) exists for this concern, discontinue this test and follow Technical Service Bulletin (TSB) instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new upper and lower high voltage battery. For the upper high voltage battery,
REFER to: High Voltage Upper Battery (414-03A High Voltage Battery, Mounting and Cables, Removal and Installation).
For the lower high voltage battery, REFER to: High Voltage Lower Battery (414-03A High Voltage Battery, Mounting and Cables, Removal and Installation).
No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.


The Service Manual says this about the P0A95:
P0A95:00 High Voltage Fuse: No Sub Type Information A fault is indicated when the BECM measures less than an expected amount of voltage at a certain internal point in the high voltage battery when module is first powered on. When this fault is present, the high voltage battery does not charge and the powertrain malfunction (wrench) warning indicator illuminates in the IPC . If this fault is cleared or repaired while the ignition is ON, the ignition must be cycled from ON to OFF and back to ON before the BECM commands the contactors to close again.
D2 VERIFY CORRECT LOWER HIGH VOLTAGE BATTERY SERVICE DISCONNECT PLUG INSTALLATION
Ignition OFF.
Depower the high voltage battery.
REFER to: High Voltage Battery Disconnect and Connect (414-03A High Voltage Battery, Mounting and Cables, General Procedures).
Remove the lower high voltage battery service disconnect plug. Inspect both sides of the connection for damage, and repair as necessary.
Install the lower high voltage battery service disconnect plug, making sure it is correctly seated.
Repower the high voltage battery, making sure the upper high voltage battery service disconnect plug is correctly seated.
REFER to: High Voltage Battery Disconnect and Connect (414-03A High Voltage Battery, Mounting and Cables, General Procedures).
Connect the diagnostic tool.
Ignition ON.
Enter the following diagnostic mode: Clear DTCs - BECM .
Ignition OFF.
Ignition ON.
Enter the following diagnostic mode: Self Test - BECM .

Is DTC P0A95:00 retrieved during the self-test?

Yes GO to D3
No The concern may have been caused by a damaged or incorrectly installed lower high voltage battery service disconnect plug. RETURN the vehicle to the customer.


D3 CHECK THE HIGH VOLTAGE FUSE FOR AN OPEN CIRCUIT
Ignition OFF.
Depower the high voltage battery.
REFER to: High Voltage Battery Disconnect and Connect (414-03A High Voltage Battery, Mounting and Cables, General Procedures).
Remove the lower high voltage battery service disconnect plug. Inspect both sides of the connection for damage, and repair as necessary.
Measure:


Positive Lead Measurement / Action Negative Lead

Lower high voltage battery service disconnect pin 1, component side
Lower high voltage battery service disconnect pin 2, component side


Is the resistance less than 3 ohms?

Yes CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a Technical Service Bulletin (TSB) exists for this concern, discontinue this test and follow Technical Service Bulletin (TSB) instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new upper and lower high voltage battery. For the upper high voltage battery,
REFER to: High Voltage Upper Battery (414-03A High Voltage Battery, Mounting and Cables, Removal and Installation).
For the lower high voltage battery, REFER to: High Voltage Lower Battery (414-03A High Voltage Battery, Mounting and Cables, Removal and Installation).
No INSTALL a new lower high voltage battery service disconnect plug.

Hoping your problem is just a loose connector and loose service disconnect.

 

[Focus_pilot]

Heima,

Thanks for the reply! That certainly gives me an awareness of what’s going on. I am going to have it towed tomorrow and hope for the best!

 

[Focus_pilot]

For my 2018 FFE, dealer just told me the contactor code troubleshooting has led to the battery as you guys predicted. Awaiting Ford to figure out the way ahead.

 

[triangles]

Glad you are still under warranty. Keep us updated as to how things go.

 

[Focus_pilot]

My Focus was towed to the dealer last week Monday. Still waiting for them to decide on the way ahead.

 

[dlinehan]

I am glad that yours is under warranty. I have a simular problem only for mine it is "multiple contactors stuck open". My battery warranty ended one month before I took to to the dealer. They are quoting $15,500 for the battery.

I am trying to appeal this to Ford. If that does not work then I am looking for a replacement junk yard battery or trying my hand at replacing the contactors. I am confident in my ability to not get electrocuted but less confident in my ability to work on their proprietary systems.

Does anyone know if the contactors are intigrated in some board once I open the pack, are they off the shelf contactors? Ofcourse, maybe the problem is not actually the contactors which cause them to get stuck open. Where can we go for technical help?

Devin

 

[Heima]

Whats got me is how does a contactor "stick" open. Open is the normal unenergized state. Do they mean the coil inside the contactor is open? Meaning there is a break in the windings? When a contactor "sticks closed" it means it is literally welded closed. This can happen if the precharge resistor or precharge contactor fails and there is too high of potential across the contactors contacts when it closes. The inrush current is so high it melts the contacts and they weld closed. Replacing the contactors solves the immediate problem, but you also have to investigate why the precharge circuit is not functioning properly.

Those who have disassembled their HV batteries might be able to answer this question: are the contactors located behind the service panel on the LH front of the upper battery pack?

 

[Anti_Climax]

It's pretty common to use "Relay stuck open" to describe a contactor that isn't closing when it should, regardless of the specific cause.

Would be interesting to see what is going on in there.

 

[Focus_pilot]

I drove the car pretty hard today and when I got home to charge, I received a charging fault. When I went to turn the car on, I received the stop safely now. I check the codes and it shows Battery Contactor A stuck closed, P0AA1 and P0A95 High voltage fuse A. Anybody seen this before?

So finally got the car back today after about 3 weeks. They replaced the HV Battery with a remanufactured battery, replaced a filter assembly, and added some anti-freeze. I don’t expect to get more range, but we will see!

 

[davideos]

I just replaced the positive contactor in the upper battery pack to fix the following DTCs: P0AA1, P0AA0, and P0A95. The contactors are on the drivers side. There are 2 larger contactors and 2 small contactors. The small ones are for pre-charge through a resistor so when the main contactors engage, they don't spark and wear out the contactor, I presume.

A tell tell sign of the bad contactor is the top of it turning brown. What I think happens is that the contacts build up some sort of resistance and when pushing current through a resistance, heat is created. Mine measured about 3 ohms. At 3 ohms and 50A. P=I^2*R, or 2500W. So I think what happens is the contactor, which is made of plastic, heats up and deforms and causes the contactor to stick.

Anyway, it isn't a hard job, but with the high DC voltage, precautions should be taken. With the service disconnect removed, it appears (from what I measured) that all the open contacts are 0. But I still used insulated tools and High Voltage rubber gloves. $14,000 is a lot for a battery replacement, but not worth dying for. I put a write up on the Focus Electric forum on Facebook.

 

[Anti_Climax]

It's likely turning brown after the contacts welded, though the root cause isn't all that different.

 

[davideos]

Actually, the terminals are not welded together. After I pulled the old contactor and confirmed that it was stuck closed, I put it on my bench and applied 12V to the input and it freed up the mechanism and it was no longer "stuck" However, the resistance was more than desirable. I think it was around 3 ohms. I forget what the specs should be, but I think it is supposed to be in the milli-ohm range.

Does anyone know if the Forscan software running on a laptop can command the contactors? It would be a good way to test a stuck contactor in the future.

 

[Anti_Climax]

A weld need not be permanent, just enough for it to stay stuck after it should be open. They can even break free once they cool down and contract. But from that point on they are hosed.

 

[emo]

Is anyone has that problem with the contactor stuck closed on a mondeo

 

[emo]

Is anyone has that problem on mondeo hybrid mk5. Olso my hybrid battery indicator shows empty. Any ideas what supposed to be done. Thanks

 

[Jpapa]

I work at Ford as a service tech and we have seen this code and “contactor stuck open” numerous times. The fault is misleading and we do not replace the battery. We remove the battery, take the cover off and replace the contactor board which has a blown high voltage fuse. Ford is aware of it and hasn’t addressed the root cause but it’s pretty common. The contactor stuck open is just a way the computer lets you know that it can’t close it because the fuse is blown.
There are two contractors. One is in series with a resistor that prevents the initial contactor from welding itself shut when the key is turned on and the battery is connected to the motor controller which has a capacitor bank. The second contactor is supposed to close a fraction of a second later to bypass the resistor. If the second contactor doesn’t close or doesn’t close at the right time, the first contactor can be overloaded from the inrush current. Replacing the board with the fuse and both contactor is the fix but not a permanent solution.

 

[Heima]

Thank you for the inside information Jpapa!