See if this helps your fan problem...
Problem
For C4 Corvettes with dual fans, the Aux Fan Sw only controls the auxiliary fan. The ECM controls only the main fan. When a low temperature Aux Fan Sw is installed to compliment a low temperature thermostat only the auxiliary fan comes On at a lower temperature; the main fan still comes On at the stock setting. This often results in inadequate air flow to properly cool the radiator in slow moving traffic.
Solution
Jumper the Aux Fan Sw Grn/Wh lead into the the Grn/Wh lead comming from the control pin of the main fan relay. This allows the Aux Fan Sw to turn On the main fan along with the auxiliary fan. The ECM can still turn On the main fan should the A/C pressure sw demand it.
Materials
- (2) insulation displacement wire splice connectors
- (2) crimp connector plugs to fit the splice connectors
- enough 18-20 Ga stranded jumper wire to reach from the Aux Fan Sw to the main fan relay (Grn is an appropriate color).
- several black wire ties
- black plastic electrical tape
Component Location
1) The Aux Fan Sw is located in the left side of the block below #1 & #3 spark plugs.
2) On a 1988 Corvette, the main fan relay is located on the inner rear of the left fender well; here the length of jumper wire was about 1 ft.
Preparation
1) Locate the Aux Fan Sw and the main fan relay and determine the correct jumper wire length.
2) Verify that the wire colors match those described here and update any differences.
3) Purchase the required materials.
4) Disconnect the battery lead.
5) Strip the ends of the jumper wire
6) Crimp the two plugs onto either end of the jumper wire.
Procedure
1) Pull some of the Aux Fan Sw Grn/Wh wire out of the wire harness that runs along the left inner fender well.
2) Carefully crimp a splice connector onto this wire so that it can be placed back into the harness.
3) Unwrap the wires comming from the main fan relay to expose a length of the Grn/Wh control wire.
3) Carefully crimp the other splice connector onto this wire.
4) Dress the jumper wire along the wire harness between the Aux Fan Sw and the main fan relay.
5) Plug the jumper wire into the two splice connectors.
6) Wrap each splice with black plastic electrical tape.
7) Open the wire harness, cutting any necessary wire ties and press the jumper wire and connector(s) into the harness.
8) Close the harness and secure with wire ties to prior configuration.
9) Reconnnect the battery lead, start the engine and observe that both fans come On at the temperature setting of the Aux Fan Sw.
NOTE:
1) The required mateirals can be purchased from a general electronics supplier like Radio Shack for $5-$10.