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4327 OREGON ROAD March 11, 2007 90-96 Fuel Meter The 1990-96 Corvettes have a CCM (Central Control Module). The fuel tank sender sends a zero to 90 ohms resistance signal from terminal B on the fuel sending connector to the CCM. Zero ohms means empty, 45 ohms means half tank, and 90 ohms means full tank. The CCM looks at this signal and puts it in memory. Any radical change of resistance may not show up at that time. If the logic is pulled low a new reading is put into memory. This can be done by grounding the cavity B wire. An open signal is indefinite ohms. The CCM looks for a zero to 90 ohms signal. To test the fuel meter, remove the gas lid assembly’s four #15 Torx screws and remove it. Unplug the sending unit. If the tank is full you should read 90 ohms using a digital volt ohm meter on the sending unit’s plug. Remove the meter and with the float arm down, the ohm reading should read zero. It is a linear signal. This means a constant change rate to full. Move the arm upwards. The ohm resistance should change to a maximum of 90 ohms at the full position. If this checks out, check the connectors inside the car where the tail light harness wire connects to the rear body harness wire. COUPE: The connection is behind the right lower side glass garnish molding. CONVERTIBLE: The connection is under the carpet rearward of the right rear deck lid area. This is a common spot for corrosion. The next connection is under the right dash where the rear body harness wire connects to the dash harness wire. Go to Radio Shack and get a 45 ohm one-half watt, and 90 ohm one-half watt resistors. Use these to test the signal wire at each connection. If all checks are good, look for a defective CCM. Most commonly it is the sending unit in the fuel tank, or corrosion at a rear connection.
AC C60 & C68
If you have a C60 (manual AC) the fan switch on the dash control-head switch sends out a signal to a resistor module in the heater casing (under the hood in the AC evaporator casing). The wires are: yellow = 1st speed; tan wire = 2nd speed; and, light blue = 3rd speed. The proper voltage leaves the resistor module on a dark blue wire that goes to the blower relay that is also attached to the evaporator casing. The high speed signal leaves the fan switch and goes directly to the blower relay, cavity D. The blower relay is grounded along with the blower motor’s ground to the engine at the top left bellhousing bolt. This is the black wire in the relay connector, cavity C. The red wire in cavity A goes to a fuse link at the starter solenoid. If you have a C68 (automatic AC) the fan speeds are controlled by the dash AC control head and a blower module in the evaporator casing. It is in the place of the manual AC resistor module. If the blower feedback wire from the blower module to the control head goes open the fan will go high speed even in the off position. Check the blower module first.
GORDON KILLEBREW
To get your personal questions answered by Gordon, call 1-800-For Your VETTE (39 83883). |
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