RTE Switch Faq
From RTE
How do you test a 1970-71 Ebody 3 speed wiper switch?
This originally came from a switch testing document I found on www.moparts.com. I decided to add some more info to the original faq and make it a little easier to read, and added some pictures.
The 3 speed wiper system controls the speed by use of a resister in the switch, not in the motor. The switch also reverses the current to the motor in the "off" position, which causes the motor to seek the "home" position. There is also a circuit breaker built into the switch to protect the circuitry.
Testing the switch
There is a test for the switch that can be done with a continuity tester or an ohmeter. To do this test, on the back of the switch, the terminals are marked with an"A", "B", "B/U", "F1", "F2", "P" and "W". In the tests, "Ground" is the switch casing. (Note: The 72-4 3 speed wiper switch has the same terminals in a slightly smaller format, so the same instructions should be applicable with some changes).
- Step 1: Check for continuity between B and B/U. In between the B and B/U terminal is the internal circuit breaker inside the switch. If there is no continuity between B and B/U, then the circuit breaker is open. This part of the switch is in the back of the switch and it is probably not possible to repair it if it is open, since it is covered up even when the switch is open. Make sure that there is no glass beads in the middle of the breaker contacts by blowing out the contacts with air. The contacts are underneath the copper about in the location where the X is. The contact is between the silver metal and the B terminal on the back of the switch. The copper pointed to by the arrow is not connected to B or B/U.
- Step 2: The windshield washer switch motor is controlled from the W terminal. When you press in the switch rotor, then the B/U and the W terminals should be connected togther, and W should be open when not pressing the switch rotor.
- Step 3: Switch the switch to the off position (all the way counter clock wise.) Check the following for continuity:
B/U to P
A to F2
(If these two fail to work, sometimes you can bend the two wipers so that the middle where the spring pushes up is lower. As you can see I bent these.)
F1 to Ground (If this fails to work, sometimes you can bend up the copper on the back of the switch where the wiper contacts. This tends to get bent down away from the wiper over the years. As you can see, I bent this one up.)
- STEP 4: Move the switch 1 click clockwise. Now test the following for continuity:
“LOW”
B/U to A
A to F1 (Should be 0 ohms)
F2 to ground
- STEP 5:
As you move LOW to HIGH, the A to F1 reading should vary from 0 ohms at low, to 25 Ohms when on high.
"HIGH" B/U to A
A to F1 (vary from 0 Ohms on low to 25 Ohms on high) F2 to ground
The wiper is connecting between this copper contact and this wirewound resistor as you vary from low to high.
How do you test a 1970-71 Ebody 2 speed wiper switch?
- Step 1: Check that B and B/U terminals have 0 Ohms between them. There is a circuit breaker between B and B/U terminals. If this breaker is open there is no known way to fix it, other than wiring in an external breaker.
- Step 2: Check that the ground strap on the side of the wiper switch has 0 ohms to the case of the switch. If this is open or high resistance, resolder it to the case.
- Step 3: Check the switch against the following table for each position:
| A | P | H | F2 | |
|---|---|---|---|---|
| Off | GND | B/U | OPEN | OPEN |
| Low speed | B/U | OPEN | OPEN | GND |
| High speed | OPEN | OPEN | B/U | GND |
How do you test a 1970-74 Ebody dimmer switch?
The Ebody dimmer switch is the same between the Rallye and non-Rallye, and it is the same from 1970 through 1974.
The dimmer switch has two functions. The first function is to turn on and off the dome light when the switch is rotated to the most counterclock-wise position. The second function is to control the brightness of the dash lights. The dash lights are most bright when the switch is rotated all the way counter clock-wise. The dash lights are off when the switch is rotated all the clockwise.
There are three terminals on the dimmer switch, and the case of the dimmer switch is connected to ground. The three terminals are labeled D, R, I on the dimmer switch:
The dome light function is activated by the terminal D being connected to ground. +12V is supplied to the dome light all the time, and the 2nd wire going to the dome light is grounded to turn the light on. The dimmer switch can ground the wire, or the door switches can also do this function.
To test this function, you should get continuity between terminal D and the case of the switch when the switch is rotated all the way counter-clockwise. Note that the switch knob is required to be on the switch in order to get enough torque to be able to get the switch rotated so that the copper strip contacts D (or you can use a pair of pliers). If you don't get continuity, then there are two possible problems: 1) the copper strip is not contacting terminal D, or the copper strip and the terminal are corroded. Both of these problems can be fixed by bead blasting the copper strip and terminal D when the switch is not closed. When bead blasting the switch don't blast the wiper contact, if you do it will knock off or bend the wiper contact. 2) If the copper strip doesn't contact the casing of the switch, then you can bead blast the area where it contacts and then solder the copper strip to the aluminum casing. You can tell that this is the problem by checking continuity between the copper strip and the aluminum case.
Here is a picture of the copper strip that contacts terminal D:
The second function (dash light brightness) is controlled by a wire wound resistor and a wiper that touches the resistor. The R terminal is connected to the wire wound resistor through the center of the bottom of the switch. The I terminal is connected to the wiper that contacts the wire wound resistor. As the switch is rotated, then the resistance between R and I will be varied from 0 Ohms to about 20 Ohms. If the switch won't go all the way down to 0 Ohms, then you may need to open the switch up and gently bead blast all the copper contacts and the wire wound resistor and the wiper. Note that the switch opens up to infinite resistance (to turn off the dash lights) when the dimmer switch is rotated allt he way clockwise. In this case the wiper is no longer touching the wire wound resistor at all.
How do you test a 1970-74 Ebody Headlight switch?
The Ebody headlight switch is the same between the Rallye and non-Rallye, and it is the same from 1970 through 1974.
The headlight switch has two functions. The first function is to turn on and off the driving lights and internal dash lights when the switch is in the middle position. The second function is to turn on the headlights when the headlight switch is in the top position. When the headlight switch is in the bottom position, then all lights are off (except that the dome light can still be turned on from using the dimmer switch).
There are four terminals on the headlight switch: B1, R, B2, H.
When the headlight switch is off (i.e. the switch is all the way down, near the H terminal), then none of the terminals are connected. When the headlight switch is in the middle position and top positions, then the R and B2 terminals are connected together (to turn on the park lights). When the headlight switch is in the top position (near the B1 terminal), then the B1 and H terminals are connected together to turn on the headlights. When you are testing continuity between these terminals, they should be near 0 ohms, and they should not vary much when the switch is jiggled. If they vary when the switch is jiggled, then the switch should be opened and bead blasted to clean the contacts.
How do you test a B-body 68-70 Rallye dimmer switch?
This dimmer switch has the same connections as the Ebody dimmer switch, but the mechanism is slightly different. Since the connections are the same, for now please refer to testing the Ebody switch.
How do you test a B-body 68-70 Rallye washer switch?
This switch is basically a normally open momentary contact switch. To test it, just set the ohm-meter to the lowest scale (usually 0-200 ohms), and connect the two leads to the two terminals on the switch. The switch should measure infinite when not pressed, and less than 1 Ohm when pressed.
How do you test a B-body 68-70 Rallye light switch?
There are five terminals on the headlight switch: B1, R, B2, H, and P. According to the wiring diagrams, P is only used on 1968 chargers.
- B1=Battery 1
- B2=Battery 2
- H=Headlight
- R=Rear lights (and on 69-70 it is also the front park lights)
- P=Park lights (only used on 1968 charger?)
The headlight switch has two functions:
1) Turn on the park lights when in position 1 on.
2) Turn on the park lights and headlights when in position 2.
- Power is supplied to the switch at terminals B1 and B2 from the fusebox.
- When the switch is off, there should be no connectivity between any of the terminals.
- When the switch is in position 1, then B2 should be connected to P and R.
- When the switch is in position 2, then B2 should be connected to R, and B1 should be connected to H.
How do you test a B-body 68-70 3 speed wiper switch?
- Step 1: Check that B and B/U terminals have 0 Ohms between them. There is a circuit breaker between B and B/U terminals. If this breaker is open there is no known way to fix it, other than wiring in an external breaker.
- Step 2: Check that the ground strap on the side of the wiper switch has 0 ohms to the case of the switch. If this is open or high resistance, resolder it to the case.
- Step 3: Check that the resistor on the switch is 27 Ohms.
- Step 4: Check the switch against the following table for each position:
- NOTE: The terminal R is not labeled, but is the top right terminal connected to the resistor.
| F1 | F2 | P | B | A | R1 | ||
|---|---|---|---|---|---|---|---|
| Off | GND | OPEN | BU | BU | OPEN | OPEN | |
| Speed 1 | 27 Ohms to R1 | GND | OPEN | BU | BU | OPEN | |
| Speed 2 | 0 to R1 | GND | OPEN | BU | BU | OPEN | |
| Speed 3 | 0 to R1 | GND | OPEN | BU | BU | F1 |
How do you test a B-body 68-70 2 speed wiper switch?
- RTE needs help on this one, anyone out there have instructions on this one?