1970 Electra Delay Wipers
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Background

First up, you should probably go read my page on delay wipers - there is a lot of good info on there, and the details on converting my 1973 Electra to delay wipers are the background information for these notes. I am using the 1973 -> 1974 delay wiper conversion as the basis for this conversion work. GM did not offer delay wipers until 1974 and the dash switches changed a lot between 1970 and 1974, so I can't simply use the later model dash switch. However, the motor wiring is the same, and a quick check of part numbers on http://ww.rockauto.com shows that the wiper motor used in 1970 until part way through the 1973 model year were the same part number. I already know that the 1974 delay style wiper motor should interchange with the 1973 non-delay wiper motor, so chances are that the delay style wiper motor will bolt right up to my 1970 Electra. If so, that would leave wiring up a suitable switch to control things. They key here is to get this to work without drilling holes in the dash and without doing massive non-reversible surgery on the wiring harness.

This was originally part of the main page about my 1970 Electra, but it got too long and was moved to it's own page.

 

Washers

I'll start with the washer system because I figured that out first. In the non-delay systems, pushing in the washer switch when the wipers are off physically moves the wiper switch to the low position. The delay style switch does not do this, instead it uses the delay controls and wiring to accomplish a few sweeps of the windshield and then automatically turns off the wipers. I've taken apart the switch from a 1973 Electra, and the mechanical change should be pretty easy - there is a ramp underneath the washer button that causes the switch lever to move when the washer button is pushed in. Physically cutting that ramp off should cause the washer button to act like the delay style switch from a mechanical perspective. From an electrical perspective, on the delay style switch there are three wires connected to ground by depressing the wash button - the pulse relay (terminal #6 on wiper motor, dark green wire in separate delay harness), the gearbox relay (terminal #1 on wiper motor, light blue with black in harness), and the washer pump relay (terminal #4 on wiper motor, dark blue wire in harness). The original switch only grounds one of these wires - the washer pump relay. The other two wires can be connected to the washer pump wire using diodes (to prevent the power from feeding back into the harness) to get the same effect.

 

Switches

For the original non-delay switch, I need it to control the low and high wiper speeds - I'll have to put the delay wiring into a separate switch. For the high speed setting, It looks both the non-delay and delay style switches simply ground the light blue with black wire connected to terminal #1 at the wiper motor. For the low speed setting, it looks like both switches simply ground the same wire as the high speed setting plus the black with orange wire connected to terminal #3. For the off position, both switches ground the black with orange wire from terminal #3 only. This gets us the basics, except for the dark green pulse relay wire from terminal #6 - the delay switch grounds this wire in the low and high settings, but not in the delay setting. This can be accomplished by connecting it to the light blue with black wire from terminal #1 with a diode to prevent power from feeding back through the system.

The problem then becomes how to recreate the wiring for the delay section of the switch. In the original delay switches, the low setting was the same as the shortest delay setting, and there was a variable resistance (0 to approx 1.2 meg ohm) to set the delay intervals. The variable resistance is also inline with a fixed 400 - 1500 ohm resistor such that power flowed into the fixed resistor, then to the variable resistor in the switch, then out to terminal #7 on the wiper motor via a white wire. When in the delay setting, the delay switches did not ground the dark green pulse relay wire from terminal #6 - this was done by the timing circuit internal to the wiper motor for each cycle. This can be accomplished external to the original wiper switch by using a variable resistor with a separate contact in the "off" position. In the "off" position, the pulse relay wire would be connected as a "pass through" to go to the original switch for connection there. In the "delay" position, the pulse wire would not be connected, and the variable resistor would be. In the "off" position, the variable resistor would be connected via the fixed resistor to give a minimal resistance value to provide low speed operation. This type of variable resistor with a switch is commonly used for volume controls in stereo equipment and is available in various resistance values - look for a "potentiometer with a combo switch". I got mine at Fry's along with the diodes I needed.

For those trying to keep track of this but failing, I created a small Excel spreadsheet to list out all of the connections and what they needed to be.

 

Wiring Diagrams

Digesting all that and messing about with some wiring diagrams, here's what I came up with as a first attempt using all relays. I knew it would be a basic first attempt, but it was a start and I've preserved in here to demonstrate the thought process I was going through.

After completing the "All Relay" diagram, I realized that two of the relays could be eliminated and while doing that I found a flaw in the circuit that needed to be fixed. The pulse wiper relay wire - the green wire - needed to be grounded directly when the wiper switch was in the "off" position, but still needed to be controlled by the relay that controlled it in the diagram above. So, I added an extra relay for that and eliminated the two high/low relays for a net gain of one relay.

After that, I realized that the relays used here are all controlling very low power - each only controls the relay coil of a different relay - and thus they can be small PC board mountable 1A relays. That meant the diodes, the resistor, and the relays in the circuit could be combined onto a single circuit board and mounted into a simple box. There are thirteen wires that need to go to this section of the circuit, breaking them down logically you get one six wire connector for the wires coming in from the wiper motor, one six wire connector (installed backwards from the first one so they cannot be interchanged accidentally) to connect to the wires going to original dash switch and to the new delay control potentiometer, and a final single wire connector to provide a ground connection. This circuit is the one I will attempt to build and verify if this works as expected or not.

 

Control Inversion

This last diagram was something that resulting from some of the thinking I was doing on this project. It's an idea for taking a GM "ground side controlled" wiper switch and using it to operate a "power side controlled" wiper motor and washer pump - aka, for use in controlling non-GM wiper motors. It also adds a separate delay settings knob. The separate control is a simple on/off volume control style potentiometer that is wired into the circuit such that when the main wiper switch is in the "low" position, the delay control allows you to select either "low" mode (potentiometer in the "off" position) or a variable delay mode (potentiometer on and set to any setting). A wash wire is provided to turn on the washer pump and an Off connections are also provided for motors that require power to park.

To make the wash circuit work right, you need to modify the original GM wiper switch to not push the lever to "low" when you depress the wash button. Column mounted switches may or may not have the same problem - I can only speak for the dash switches I've been working with.

The relays used here would need to be sized to match whatever they were controlling. If they had to take the full power of the wiper motor, 15A relays would be a good guess. This is quite different than the circuits above where the relays shown in my circuits are only controlling other relays and thus I could use very low-capacity 1A relays.

Please note that this circuit is completely unsuitable for controlling a GM wiper motor. The whole purpose of this circuit is to control a non-GM wiper motor with a GM dash mounted wiper switch. With any luck, GM column mounted wiper switches will be wired similarly to the older dash-mounted switches and the basic principles demonstrated here may be able to be applied to column mounted switches as well.

Various wires in this circuit can be removed or modified if desired for your particular application. This is just an idea to get you started and was an outgrowth of work I did on adding delay wipers to my 1970 Buick Electra.

 


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Page last updated 01/02/2009 01:51:39 PM