What happens if I connect the lift retrofit kit with reversed polarity?
Reversed polarity carries a serious risk of damage; the LFT20 has no protection circuit. Red positive, black negative; wire it with the battery negative off.
Connecting with reversed polarity carries a serious risk of damage. The LFT20 contains no board, processor or sensor, so there is no protection circuit; the motor can run in the wrong direction and strain the mechanism, and the product is in any case sold outside warranty coverage. The LFT54 has a control board embedded in the motor, but reversed polarity is not a normal operating condition on any product. The red wire goes to the positive terminal and the black wire to the negative.
The situation by model
| Model | Electronics inside | What to expect with reversed polarity |
|---|---|---|
| LFT20 | No board, processor or sensor | No protection circuit; the motor turns the wrong way and the mechanism can be strained |
| LFT54 | Control board embedded in the motor | It is supplied through the board; even so, reversed polarity is not a normal operating condition |
What sort of circuit reverse polarity protection is, and what it does and does not cover, is a separate subject in itself. That protection is present only on products whose technical specifications state it explicitly; the specification list of the HCT402, for instance, includes reverse polarity protection. There is no such declaration for the LFT kits, so protection is not assumed and the connection is made correctly. You can compare which model has what under which model has reverse polarity protection.
The sign of a reversed connection is not always smoke or a smell. In most cases the kit gives no response at all, or the mechanism moves in the opposite direction to the one expected; either is reason enough to disconnect at once.
The order that prevents the mistake
- Do the wiring with the power off. Disconnect the negative terminal of the battery, complete all the connections and reconnect it last.
- Verify the colour code. Red means positive and black means negative. Do not trust wires already run on the tractor; measure them with a multimeter.
- Confirm negative ground. Modern tractors are 12V negative ground, meaning the negative terminal of the battery is connected to the body. You should read about 12.6 V between the chassis and the positive line.
- The bench test. The test that is mandatory before installing the LFT20 already lets you check that the polarity is right; the red wire is touched to the battery positive and the black wire to the negative.
- Fit the fuse last. Do not energise the line before the connections are complete; a correction made with the fuse in place brings a short-circuit risk with it.
If you suspect you have connected it the wrong way round
Do not keep trying; every attempt enlarges the possible damage. Disconnect, check the fuse, measure the polarity with a multimeter and report the situation to technical support. You can read why the LFT20 is sold outside warranty coverage, and what that means in practice, under the relevant heading.
Against that, not every failure to work means a reversed connection. A blown fuse, a loose chassis terminal or a faulty switch give the same symptom. So once you have measured the polarity and seen that it is right, carry the search on at those three points; removing the kit is the last step.
The other moments that carry the same risk
The danger of reversed polarity arises not only at first installation. The same care is needed when connecting a jump battery, when changing the battery and when welding on the vehicle; the precautions to take where the welding current travels through the chassis are collected under protection before welding and jump starting. Show the same care over the direction of the terminals when connecting jump leads.
What to do in practice
Measure the polarity before connecting the wires, write the value you measured on a label on the wire and switch the power on last. These three steps almost completely remove the most common wiring mistake seen in the field.
The full topic: Converting a tractor hydraulic lever to electronic control