Electrical System
348
Conductance Test
This type of testing is replacing the carbon pile testing method. It is reliable and can be performed
without charging (as in step 6 above). Since no high-current loads are applied to the battery with a
conductance tester, this test is safer to perform. Use a conductance tester such as the Micro 700 made by
Midtronics, and follow the instructions included with the tester.
Specific Gravity Readings
When using a hydrometer, always wear a face shield, gloves, and
protective clothing.
A hydrometer can be used to measure the specific gravity of the electrolyte in each cell. The hydrometer
measures the percentage of sulfuric acid in the battery electrolyte in terms of specific gravity. As a bat
-
tery drops from a charged state to one of discharge, the acid leaves the electrolyte and enters the plates,
causing a decrease in the specific gravity of the electrolyte. An indication of the concentration of the
electrolyte is obtained with a hydrometer.
When performing the hydrometer test procedures given on the next page, observe the following guide-
lines:
1. The hydrometer must be clean, inside and out, to obtain accurate readings.
2. Hydrometer readings must never be taken immediately after water has been added. The water
must be thoroughly mixed with the electrolyte by charging for at least 15 minutes at a rate high
enough to cause vigorous gassing.
3. If the hydrometer has a built-in thermometer, draw liquid into it several times to ensure correct
temperature before taking readings.
4. Avoid dropping battery fluid on the vehicle or clothing. It is extremely corrosive. Any fluid that
drops should be washed off immediately with a baking soda solution.
The specific gravity of the electrolyte varies with temperature as well as with the percentage of acid in
the liquid. As the temperature increases, the electrolyte expands so that the specific gravity is reduced.
As the temperature drops, the electrolyte contracts so that the specific gravity increases. Unless these
variations in specific gravity obtained by the hydrometer are corrected for temperature, the hydrometer
will not give a true indication of the concentration of acid in the electrolyte.
Summary of Contents for LOW FLOOR
Page 18: ...Specifications 18...
Page 58: ...Preventive Maintenance 58...
Page 110: ...Engine 110...
Page 138: ...Transmission Driveline Rear Axle 138...
Page 182: ...Suspension 182...
Page 260: ...Air System 260...
Page 420: ...Electrical System 420 Deutsch DT Series Connectors...
Page 421: ...Electrical System 421...
Page 422: ...Electrical System 422 Deutsch HD 10 Series Connectors...
Page 423: ...Electrical System 423...
Page 424: ...Electrical System 424 Deutsch HD 30 Series Connectors...
Page 425: ...Electrical System 425...
Page 442: ...Heating Air Conditioning 442...
Page 492: ...Body and Interior 492 Figure 11 33 USSC Seat Assembly...
Page 493: ...Body and Interior 493 Figure 11 34 USSC Seat Suspension Assembly...
Page 495: ...Body and Interior 495 Figure 11 37 Seat Air Connections...