Troubleshooting Error Codes SH and OL on a Tekonsha Prodigy Brake Controller # 90185


The trailer brakes do not work. prodigy code is 5.H. when you press on the brake a little square o. show in the upper left hand corner and the next is L. thanks for your help,

Expert Reply:

The first error code, SH, you are seeing on the Prodigy Brake Controller, # 90185 (instructions linked below) means the brake wire sees a short circuit during idle condition. The second code, OL, indicates an overload condition during operation.

For the first code, SH, the most likely problem is a pinched wire or at some point the wire insulation has cracked or been worn to the point where the copper wire inside is making contact with the trailer frame or another metal part. To find the problem, you will need to start at the trailer connector, making sure it is not corroded, dirty, or damaged, then work your way back to the brake magnets, examining the wire as you go. The fix is to replace the damaged wire and/or clean off the connector.

The second code, OL, could be related to the first. A short between the brake output pin and the ground pin on the 7-Way could cause an overload. Cleaning the connector of any dirt or corrosion would be the first thing to try. If you still have the same problem, sever the connection of the blue wire at the back of the brake controller. Leave enough wire to reconnect the wire after testing.

Once the blue wire is severed, if the brake controller returns to normal function and the decimal point returns on the display, you know that the problem is on the blue wire somewhere between the controller and the connector at the rear of the vehicle. You may need to run a separate 10 gauge wire, # 10-1-1, to the trailer connector to bypass the problem, unless you can locate, isolate, and repair the bad spot in the wire.

Last, the brake magnets themselves could be going bad or gone bad. I would check the magnets for wear before going on to test them with a meter. If the magnets show abnormal wear or if you can see the windings beginning to show through the friction surface of the magnet then they will need to be replaced.

To further test your magnets, first make sure the trailer is not connected when performing this test. If the trailer is connected, you run the risk of shorting out the brake controller or various other electrical components.

To test the brake magnets with an ammeter, connect the ammeter between the positive battery terminal of a separate battery and one of the magnet wires. Then, connect the other magnet wire to the negative battery terminal. Check the amperage, if the amperage is greater than the specified amount in the chart below, replace the magnet. If the reading is less than the specified amount, then the leads are bad and the magnet should be replaced.

Electromagnet Specifications:

7 inch Diameter Brake Drum:
Max Amps at 9-10.5 Volts
2 Brakes 4.7-5.6
4 Brakes 9.5-11
6 Brakes 14.3-16

Max Amps at 12-13 Volts
2 Brakes 6.3-6.8
4 Brakes 12.6-13.7
6 Brakes 19.0-20.6

10 and 12 Inch Brake Drums
Max Amps at 9-10.5 Volts
2 Brakes 5.6-6.6
4 Brakes 11.3-13.3
6 Brakes 17.0-20.0

Max Amps at 12-13 Volts
2 Brakes 7.5-8.2
4 Brakes 15.0-16.3
6 Brakes 22.6-24.5

Next, disconnect the negative wire from the brake magnet wire and connect it to the base, housing, of the brake magnet. If there is any amperage, the magnet is shorted and will need to be replaced.

Finally, using an ohmmeter, check the resistance between the brake magnet wires. If the resistance is not within the specified range below, the magnet will need to be replaced.

7 inch brake magnet resistance should be 3.8-4.0 Ohms
10 and 12 inch brake magnets resistance should be 3.2-3.5 Ohms

expert reply by:
Michael H

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Questions and Comments about this Question

Are the drum magnets polarity sensitive? My controller shows 2 dots in disconnect position. When trailer harness is connected I receive an SH on controller, if I step on brakes nothing changes. . If I turn lights on I get a normal reading on controller and a response if I step on brake pedal. I have a second trailer and when connected to it everything appears to be normal. All lights, on problem trailer are grounded through a common ground, which is also grounded with negative from battery to trailer frame, along with common brake negative. . All wheel brake magnets have been disconnected and reconnected to facilitate suspension upgrade.

comment by: John - 4/6/2013

Magnets are not polarity sensitive. Just get one wire to a good ground and one wire to a good connection for the controller output. Does not matter which. SH indicates a short on the brake output circuit somewhere. One magnet with a bad connection will cause it. Per the owners manual the probably causes are as follows: 1 - Brake wire sees short during idle condition 2 - Use of some test lights or non-Tekonsha testers can cause this problem

Patrick B - 4/19/2013

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