Kriss Motorcycle Products

Analysis of those things that cause damage to our circuit board.

The results shown in the examples below are very simple to evaluate as soon as a technician inspects the circuit.
The diagnosis in this autopsy cannot be more definite! It's simple indisputable and revealing engineering science.
The mosfets in this circuit simply sit and wait for something to be connected. They don't short, overload or reverse connect themselves.

We as the manufacturer make all determination of damage and cause. We do not accept assessments from untrained persons outside our company.

Nowadays, it's not often that someone tries to convince us their mistake was a faulty device.

Reverse Polarity Connections
This suppression diode can only be blown from one of the two causes.	1. When one of our units is connected with the power and ground wires reversed a typical reverse polarity situation occurs and shorts out the "Reverse polarity diode" that's installed to help protect the circuit board from suffering catastrophic destruction. After this occurrence connecting the unit, even in the correct direction, will blow the fuse in the motorcycle circuit where the unit is being connected. This design protects the circuit board in most cases. We can identify this circumstance very quickly by removing the shorted diode which then allows the unit to function correctly. The component should be replaced to offer continued protection. 2. If the unit was installed correctly and didn't suffer reverse polarity and the unit has been working fine for an extended period of time and then blew it would indicate that there is a problem within the bikes electrical system that's caused a over voltage (above 18 volts) or high voltage spike in the circuit. The component can be replaced but until the voltage regulation problem is fixed it's likely the diode will blow again.

MOSFET DESTRUCTION (Metal-oxide semiconductor field effect transistor) These are the components that control switching of power to the lights or accessory.
The Mosfets we use have positive voltage applied to the input side and are controlled by a positive signal applied to what's called the gate to turn off the positive output. Since negative voltage isn't applied to the Mosfet it's not possible for it to short circuit itself. The device simply acts like a switch that sits and waits for something to be connected so it doesn't short out internally on it's own resulting in these kinds physical damage.
Results of a short circuit
Left circuit Mosfet is in good condition. Right circuit Mosfet has top blown off.	When the Mosfet device is connected and is subjected to an excessive amount of current flow in a very short period of time, due to a simple short circuit in the external wiring for that part of the circuit, the component blows apart. The Mosfets we use are normally ON and turned off only when needed so in most cases the Mosfet will not turn off any longer after this kind of failure and the light remains ON steady. Overload from the use of a larger bulb than the Mosfet is rated can result in cumulative heat damage.
Result from reversing the in and out connections
Heat melted the solder and the lower Mosfet fell off of the small solder pads on the circuit board.	When the Mosfet is connected backwards (in and out are reversed) the internal structure will permit current flow by what's called the intrinsic diode. The light or bulb being powered will come on for a brief period because the current is flowing uncontrolled and then go off after the Mosfet is burned up. The Mosfet will heat up significantly, during the reverse current flow, over a period of a few seconds and burn up (disintegration) because of the high heat accumulation. The generated heat is usually significant enough to damage the circuit board and the pads that the Mosfets were sitting on.

Results of no ground connection

When the ground connection is overlooked or comes loose the Mosfets go into a high
speed oscillation because the gate doesn't know what state to be in and doesn't
control the current flow. This generates excessive heat in a period of a few seconds
resulting in melt down.

Closer view

Reverse connection and lack of ground are the most catastrophic type of failures.

September 2007 - In an effort to conform to today's market place and recognizing the importance of prices to the American consumer it was necessary to streamline our operations offering services in line with the rest of the industry. For years we were the only company spending valuable resources offering repair services for items damaged during installation or other events, like an accident, however we can no longer provide repair services or custom modifications or custom built electronics. Allocating fewer resources meant our repair services had to be eliminated. We wish this could have been avoided but when people want to buy something at the lowest possible price some kind of service always has to be cut.
Damaged items will need to be replaced.