SLC Free Troubleshooting

[Alan To]

I will continue to add to this post as time goes on.

Basic Functional Test:

With the sensor connected, power up SLC Free. 

Over a Period of ~1 minute the temperature displayed on the LCD should:

-For SLC Free A/B (LSU 4.9) go from 740 to ~825C, at the end of the minute it should settle to 780C +/- 25C

-For SLC Free C (LSU 4.2) go from 670 to ~800C, at the end of the minute it should settle to around 750C +/- 25C

Over the same 1 minute period the displayed Lambda value should change from ~1.00 Lambda (usually it starts off @ 1 Lambda, if it is significantly different it is still ok because when the sensor is cool; behavior is not always predictable) to 1.36 Lambda. 1.36 Lambda is the leanest SLC Free can read, so in free air it will show the max lean limit it can read. 

Over the same 1 minute period the sensor should get hot, be careful the sensor can get very very hot.

Once the Displayed temperature settles to 780/750, take a lighter and give the tip of the sensor some gas, do not light the gas, with enough gas SLC Free will show the max rich it can read; ~0.68 Lambda.

Basic Functional Test Failure- Displayed temperature does not change from 670/740, Displayed Lambda does not change to 1.36 Lambda, and sensor does not get hot:

Generally this is caused by the sensor not heating up

-Make sure that both the "electronics ground" and the "Heater ground" on JP1 is grounded

-Check over the power cable and the sensor cable with a continuity tester, and check that the sensor cable is properly made according to the SLC Free User Manual

Power off SLC Free, disconnect the sensor, power on SLC Free. With a multimeter check the voltage of the left most pin on Q1 (IRF3710).  When the unit is first powered on; the voltage on left most pin should go from 2.2v to 5v over a period of about 1 minute. If the voltage does not change, then Q1 is blown and needs to be replaced. 

Power off SLC Free, disconnect the sensor, Place a resistor (I suggest a 10k resistor) between terminal "3" and terminal "4" of the sensor connector, Power on SLC Free. Use a multimeter and check both ends of the resistor, when the unit is first powered on, one end of the resistor should be a constant ~12v, the other end of the resistor should start out at ~7v and slowly decrease to ~0v over a period of about 1 minute. If you get different behavior then either your cable is defective or Q1 (IRF3710) is blown.

The only reason Q1 will blow is that the user disconnects of connects the sensor while SLC Free is powered. The first page of the SLC Free User Manual in red bold letters under the "Warning" heading tells the user not to connect or disconnect the sensor while SLC Free is Powered.

Common Problems:

The most common problem is the power and sensor cable, specifically the molex contacts in the beige molex connectors. After you made your cables, plug the cables into SLC Free, use a multimeter and check the continuity between the pinheader (soldered to the PCB) and the opposite end of the cable.

[Paweł Sir_emak]

I am making test with 10k resistor between terminal 3 and terminal 4 of the sensor connector. After power on one end of resistor slowly decrease from ~7v to 0v, when it reach 0v then it rapidly increase to 12v and stay on it. Is it normal behavior?