Instructions for Determining The Secondary Voltage of the Transformer{1555, 7620} Caterpillar

Engine:

G3516C (S/N: GSB1-119; GZZ1-252; RWA1-158; TJB1-UP; TJC1-UP)

G3516E (S/N: GAS1-246; SLY1-UP)

G3520C (S/N: B9P1-UP; CWW1-UP; CWY1-UP; GDB1-50; GHE1-251; GZJ1-328; GZK1-182; GZL1-145; GZM1-183; GZN1-615; HAT1-UP; HEA1-UP; HEB1-UP; HET1-UP; JBZ1-113; MAD1-UP)

G3520E (S/N: GHR1-152; GZG1-111; GZH1-133; HAL1-UP; SXY1-UP)

Introduction

This Special Instruction provides the procedure that is necessary to obtain an accurate display of the "% Secondary Voltage". The "% Secondary Voltage" of the transformer is used with the Engine Ratings Electronic Software Group. The "% Secondary Voltage" will be displayed on Caterpillar Electronic Technician. Refer to Table 3 for details about the transformer.

Important Safety Information

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools in order to perform these functions properly. Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. If a tool, a procedure, a work method or operating technique that is not specifically recommended by Caterpillar is used, you must ensure that it is safe for you and for other people to use. You should ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance or the repair procedures that are used.

Information for the System

The "% Secondary Voltage" is the portion of the maximum voltage of the transformer that is used by the spark plug.

Note: If the maximum voltage of the transformer is 35000 volts and the spark plug is firing at 3500 volts, then the "% Secondary Voltage" will read 10%. The "% Secondary Voltage" is obtained by dividing 3500 volts by 35000 volts.

The "% Secondary Voltage" display is provided as an indicator of the health of the spark plug and the gap wear. With new spark plugs, the "% Secondary Voltage" value will be low. As the health of the spark plug is decreased and the wear on the gap is increased, the "% Secondary Voltage" value will increase. The increase of the wear on the gap may cause the cylinder to misfire, even though the "% Secondary Voltage" has not reached 100%.

The Engine Ratings Electronic Software Group has been updated for the serial numbers listed above. If the new Engine Ratings Electronic Software Group is used, then the CAT ET Service Tool will display a more accurate "% Secondary Voltage" than the old Engine Ratings Electronic Software Group. Although the new software displays "% Secondary Voltage" more accurately, the CAT ET Service Tool may intermittently display "0" for a short time. Refer to Table 2 for the new software.

Note: The variation of a new set of spark plugs may have a range of "10 % and 30 % Secondary Voltage".

There are many factors that affect the "% Secondary Voltage" when misfire occurs. The factors include the age of the spark plug. Obtain a good historical record of the "% Secondary Voltage" when misfire occurs. The record provides an estimate on replacing the spark plugs.

Procedure

1. Use Table 1 to cross-reference the "% Secondary Voltage" for the replacement of the spark plugs.

   Note: For this example, if a system has been converted from the old software and an old transformer to the new software and a new transformer, then both Illustration 1 and Illustration 2 will be required in order to determine the new "% Secondary Voltage" for the spark plug replacement.

2. Use Illustration 1 in order to cross-reference the "% Secondary Voltage" of the old software to the "% Secondary Voltage" of the new software.

   Note: For this example, if the spark plugs were replaced at "50% Secondary Voltage" with the old software, then the spark plugs should now be replaced at "60% Secondary Voltage".

3. Use Illustration 2 in order to determine the new transformer's "% Secondary Voltage". Use the curve to identify the corresponding value for the "% Secondary Voltage" with new software and the new transformer.

   Note: For this example, locate "60% Secondary Voltage" on the x-axis of Illustration 2. The corresponding value for the new transformer "% Secondary Voltage" is approximately 63%.

   Note: Not all scenarios require the usage of Illustration 1 and Illustration 2. Refer to Table 1.

The testing procedures for the new transformers are the same testing procedures for the old transformers. Refer to Troubleshooting, RENR5944, "G3516C and G3516E Engines" and/or Troubleshooting, RENR5977, "G3520C and G3520E Engines" for the testing procedures.

Note: The new transformer has a different secondary winding resistance. Refer to Illustration 3 in order to identify the correct resistance for the new transformer.

Illustration 1	g01365195

Illustration 2	g01365198

Illustration 3	g01365199