How to convert 3 wire headlights to 2 wire CHEAP. (long and photos!) – CorvetteForum – Chevrolet Corvette Forum Discussion

How to convert 3 wire headlights to 2 wire CHEAP. (long and photos!) - CorvetteForum - Chevrolet Corvette Forum Discussion How to convert 3 wire headlights to 2 wire CHEAP. (long and photos!)

How to convert from the 3 wire headlight system to a two wire system. (CHEAP!)


First a word of thanks for help in getting this together; To Greg (nobodyunknown) who figured this out on his own and gave me the wire color codes and hookup information from his project. To Danny (route66dan) for hooking me up with Pull-a-part to get the stuff I needed.

The three wire system uses 3 relays to control the direction of the headlight motors. Inside the motor are two limit switches that shut off the motor after the headlight has stopped moving up or down. Also inside the motor is a thermal switch that will remove power to the motor if it overheats. All these switches and relays add up to one thing: unreliable and intermittent operation.

From 88 on the relays were replaced by an electronic module. The module controls the direction of the motor and by sensing the current draw it removes power from the motor when the headlights stop moving. Because the module takes care of the power shut off, the two limit switches inside the motor are not needed. On the two wire motors the module is connected directed to each of the two brushes. It reverses direction by switching the polarity of the voltage applied to the brushes.

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So much for theory. The first step is to modify the motors and make them like the two wire motors. Pull the motor off and open it up. Remove the shaft and magnet by lifting them straight up. Under the shaft is a small board that has the limit switches and brushes. Two screws hold it down. Remove the screws and lift the board out. There is a green wire and a white wire. You need to cut them and solder them directly to each of the brushes. One of them is longer than the other so they will only reach one brush each. Cut the third wire and leave it in place. You will not use it.

Reverse the order and reassemble. The board goes in first then the shaft. Three things to watch here that are important. 1. Be VERY CAREFUL not to damage the brushes. Hold them out of the way when you put the shaft back into place. (Requires 4 hands) 2. There are two springs on the shaft, one over the top of the other. The top spring MUST be biased to the inside. If it is not the shaft will not be able to be seated all the way down and the cover will not fit. 3. There is a notch on the magnet that must be aligned with a

plastic piece under the magnet. Use some black silicone around the edge of the motor to seal it. You are done with the motor. Put it back on the headlight and mount it back on the car.

The module has two plugs. The output plug has 4 wires. A and B go to one headlight. C and D go to the other. You will find the head light wires on two of the relays. Cut them off and wire them to the connector on the module. Make this a temporary connection with wire nuts or tape since you will check

the polarity later. The other plug in the module has 5 wires. B and E get +12v. Use the two red wires from the same two relays previously located and connect the wires to these pins. The third relay is the isolation relay. From it you will want the yellow wire and a grey or slate colored wire. Verify you have the right wires. The correct yellow wire will have +12v when the headlights are turned on. The correct slate wire will only have +12v when the headlights are turned off. Yellow wire goes to pin A (up) and slate wire goes to pin C.

Get the connectors wired up then connect the 4 pin output plug first. Put your headlight switch in the middle so that the parking lights are on. This removes power from the yellow and slate wires. Put the headlights half way up. Plug in the input connector. Turn on the headlight switch. If they go up you are

all set. If they go down, just reverse the connections to the headlight motor. Test again.

Mount the module and dress the wires neatly and you are done.

Note: You can find these modules and connectors at salvage yards. GM used the same module on the 87 and later Firebirds. It is located on the firewall on the drivers side. Firebirds are much easier to find than

Corvettes and they don’t want as much for the parts from them. I have been told the Fierro used the same module, but have not verified it. I paid $5 for the module and $2 for the connectors. That was my total cost for this project.

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Note 2: according to Greg you can do this without modifying the motors. I chose to open up the motors and wire around the limit switches since mine were intermittent.

Here are some pictures of the project:

http://members.***.net/rmartin24/vette/motor-open.jpg http://members.***.net/rmartin24/vette/brush.jpg http://members.***.net/rmartin24/vet…shes-close.jpg http://members.***.net/rmartin24/vet…s-modified.jpg http://members.***.net/rmartin24/vette/module.jpg http://members.***.net/rmartin24/vet…ght-wiring.jpg

If you note any errors or if something is not clear, send me an email so I can update this. [email protected]



[Modified by LaVidaLoca, 11:33 AM 2/26/2003] [external_footer]