Looking at the
wiring diagram, when you press the
convertible top switch to lower, ground is sent from terminal 2 of the
convertible top switch to terminal 4 of the
Front Electronic Module. This tells the
FEM that you want to lower the roof. The
FEM then sends a signal through the CAN bus lines to the Rear Electronic Module telling the REM to lower the
convertible top. The REM then grounds the control side of the
convertible top lower relay to energize the relay. Once the relay is energized, voltage is sent through the white wire from the
convertible top lower relay to the
convertible top motor. Since the yellow wire of the motor is grounded through the
convertible top raise relay, the
convertible top motor operates.
doug7740
1955 Thunderbird Blue
Looking at the
wiring diagram, when you press the
convertible top switch to lower, ground is sent from terminal 2 of the
convertible top switch to terminal 4 of the
Front Electronic Module. This tells the
FEM that you want to lower the roof. The
FEM then sends a signal through the CAN bus lines to the Rear Electronic Module telling the REM to lower the
convertible top. The REM then grounds the control side of the
convertible top lower relay to energize the relay. Once the relay is energized, voltage is sent through the white wire from the
convertible top lower relay to the
convertible top motor. Since the yellow wire of the motor is grounded through the
convertible top raise relay, the
convertible top motor operates.
When you press the
convertible top switch to raise, ground is sent from terminal 5 of the
convertible top switch to terminal 17 of the
FEM. This tells the
FEM that you want to raise the roof. The
FEM then sends a signal through the CAN bus lines to the REM telling the REM to raise the
convertible top. The REM then grounds the control side of the
convertible top raise relay to energize the relay. Once the relay is energized, voltage is sent through the yellow wire from the
convertible top raise relay to the
convertible top motor. Since the white wire of the motor is grounded through the convertible lower relay, the
convertible top motor operates.
Since you said that the
convertible top does not operate, as you see the cause could be the
convertible top switch, the raise relay, the lower relay, the
FEM, the REM or the wiring. Since you said that you replaced the relays, you can eliminate the relays. I don’t know how you checked the
convertible top switch, but if you diagnosed it properly we can eliminate the switch.
You said that you checked the grounds, the grounds that you need to check are; G300 at the right rear vehicle floor, and G301at the left side vehicle floor. If the interior light is working than G301 has to be okay. If the
FEM or the REM wasn’t grounded properly, then you would have more problems than just the
convertible top not operating.
Since you said that you checked fuses 14 and 31 at the battery junction box in the trunk, that leaves the
FEM and the REM. This is where you need a scan tool, preferably one with bi-directional control. When I was at the dealership, I would start by checking for faults in the
FEM and the REM and if there no faults present, I would then command the
convertible top to raise and lower using the scan tool. Remember if the CAN or Data bus wires were open or shorted, there would be CAN bus faults stored.
As biddle said, the
convertible top not functioning is a symptom of a defective
FEM, but before you start replacing the
FEM or the REM take the vehicle to the dealer, or a repair shop with the proper tools and knowledge to properly diagnose the system.
doug7740
1955 Thunderbird Blue
Looking at the
wiring diagram, when you press the
convertible top switch to lower, ground is sent from terminal 2 of the
convertible top switch to terminal 4 of the
Front Electronic Module. This tells the
FEM that you want to lower the roof. The
FEM then sends a signal through the CAN bus lines to the Rear Electronic Module telling the REM to lower the
convertible top. The REM then grounds the control side of the
convertible top lower relay to energize the relay. Once the relay is energized, voltage is sent through the white wire from the
convertible top lower relay to the
convertible top motor. Since the yellow wire of the motor is grounded through the
convertible top raise relay, the
convertible top motor operates.
When you press the
convertible top switch to raise, ground is sent from terminal 5 of the
convertible top switch to terminal 17 of the
FEM. This tells the
FEM that you want to raise the roof. The
FEM then sends a signal through the CAN bus lines to the REM telling the REM to raise the
convertible top. The REM then grounds the control side of the
convertible top raise relay to energize the relay. Once the relay is energized, voltage is sent through the yellow wire from the
convertible top raise relay to the
convertible top motor. Since the white wire of the motor is grounded through the convertible lower relay, the
convertible top motor operates.
Since you said that the
convertible top does not operate, as you see the cause could be the
convertible top switch, the raise relay, the lower relay, the
FEM, the REM or the wiring. Since you said that you replaced the relays, you can eliminate the relays. I don’t know how you checked the
convertible top switch, but if you diagnosed it properly we can eliminate the switch.
You said that you checked the grounds, the grounds that you need to check are; G300 at the right rear vehicle floor, and G301at the left side vehicle floor. If the interior light is working than G301 has to be okay. If the
FEM or the REM wasn’t grounded properly, then you would have more problems than just the
convertible top not operating.
Since you said that you checked fuses 14 and 31 at the battery junction box in the trunk, that leaves the
FEM and the REM. This is where you need a scan tool, preferably one with bi-directional control. When I was at the dealership, I would start by checking for faults in the
FEM and the REM and if there no faults present, I would then command the
convertible top to raise and lower using the scan tool. Remember if the CAN or
Looking at the
wiring diagram, when you press the
convertible top switch to lower, ground is sent from terminal 2 of the
convertible top switch to terminal 4 of the
Front Electronic Module. This tells the
FEM that you want to lower the roof. The
FEM then sends a signal through the CAN bus lines to the Rear Electronic Module telling the REM to lower the
convertible top. The REM then grounds the control side of the
convertible top lower relay to energize the relay. Once the relay is energized, voltage is sent through the white wire from the
convertible top lower relay to the
convertible top motor. Since the yellow wire of the motor is grounded through the
convertible top raise relay, the
convertible top motor operates.
When you press the
convertible top switch to raise, ground is sent from terminal 5 of the
convertible top switch to terminal 17 of the
FEM. This tells the
FEM that you want to raise the roof. The
FEM then sends a signal through the CAN bus lines to the REM telling the REM to raise the
convertible top. The REM then grounds the control side of the
convertible top raise relay to energize the relay. Once the relay is energized, voltage is sent through the yellow wire from the
convertible top raise relay to the
convertible top motor. Since the white wire of the motor is grounded through the convertible lower relay, the
convertible top motor operates.
Since you said that the
convertible top does not operate, as you see the cause could be the
convertible top switch, the raise relay, the lower relay, the
FEM, the REM or the wiring. Since you said that you replaced the relays, you can eliminate the relays. I don’t know how you checked the
convertible top switch, but if you diagnosed it properly we can eliminate the switch.
You said that you checked the grounds, the grounds that you need to check are; G300 at the right rear vehicle floor, and G301at the left side vehicle floor. If the interior light is working than G301 has to be okay. If the
FEM or the REM wasn’t grounded properly, then you would have more problems than just the
convertible top not operating.
Since you said that you checked fuses 14 and 31 at the battery junction box in the trunk, that leaves the
FEM and the REM. This is where you need a scan tool, preferably one with bi-directional control. When I was at the dealership, I would start by checking for faults in the
FEM and the REM and if there no faults present, I would then command the
convertible top to raise and lower using the scan tool. Remember if the CAN or Data bus wires were open or shorted, there would be CAN bus faults stored.
As biddle said, the
convertible top not functioning is a symptom of a defective
FEM, but before you start replacing the
FEM or the REM take the vehicle to the dealer, or a repair shop with the proper tools and knowledge to properly diagnose the system.
doug7740
1955 Thunderbird Blue
View attachment 20723
One other thing I forgot to mention is the
hardtop sense switch. If the sense switch is defective the REM would think that the
hardtop was installed, when it was not, and would not allow the
convertible top to operate. The sense switch can be checked with a scan tool monitoring the sense switch PID in the Rear Electronic Module.
doug7740
1955 Thunderbird Blue
The signal sent to the
FEM from the switch would go through the CPU, meaning if that was the issue there should be other issues related to the
FEM functions that were not functioning properly.
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