Diagnostic of Broken Lumbar Support Switch in 1999 4Runner Limited

[Nairn]

Hi,

I just bought a 1999 4Runner (Limited, V6) and my lumbar support switch in the power seat on the driver’s side does not work. Normally I would live without this functionality, but the seat is uncomfortable if I sit in it for a long period of time. I don’t have cash right now to take it to the local Toyota dealership to get it fixed.

How can I tell if the switch is the problem as opposed to the wiring or the motor? The rest of the power seat works correctly. If I test the switch and wires with a multimeter, what would I be looking for (i.e voltage, resistance)?

Thanks

 

[Nairn]

Update:
Ok, so I tested the wires and the switch with a multimeter. There are four prongs that connect the switch to the wires. I do not have a background in electronics. Can anyone tell what these results mean?

1) Wires

a. Voltage: I turned on the power in the 4Runner and make a connection between one of the wire prongs to a ground (truck frame). Three of the wire prongs had no voltage and one had 12 V of voltage (lower left prong).

b. Resistance: I tested between the various wires. Top and bottom of each side showed a resistance reading. Across and diagonally did not have any resistance.

2) Switch
Resistance: I tested the resistance between the various prongs with the switch in the off (middle) position, the ‘ lumbar move in’ position, and the ‘lumbar move out’ position. Some of the positions showed resistance while others did not.

 

[Singtoe]

If you need to move the lumbar. You have figured out half the work.

The wire that has power is the power.

The wire that is white with a black stripe is the ground.

The other two wire are the lumbar motor wires.

Cut your self two jumper wires and connect the ground to one motor wire and the power to the other motor wire.

This should move the lumbar support. If not, reverse and try again.


This will work only assuming that your switch is bad.

If the motor is bad, you might have to get a pillow.

 

[LittleCaesar]

The switch on mine went bad, or more specifically one of the connecters on the switch corroded due to moisture I believe. I found one at a junkyard for $10. From the dealer they are about $50. Your motor is still good I would bet.

 

[Nairn]

Update:

I tested by running jump wires from Pin #4 Lower left (power, 12V) to the one of the motor wires (Pin #1 or Pin #2) while the other motor wire was hooked up the ground. Nothing happened.

From a suggestion on another forum, I added jump wires between the switch and the wires coming out of the seat so that I could test the voltage as I operated the switch (4Runner power on).

Pin #4 Lower Left (power, 12V)
Pin #1 Lower Right (wire to motor)
Pin #2 Upper Right (wire to motor)
Pin #3 Upper Left (ground)

Results:
a) At all times, I get 12V on the Pin #4 Lower Left wire.

b) With the switch in forward (out position) I get power (12V) at both Pin #1 Lower Right (wire to motor) and at Pin #2 Upper Right (wire to motor).

c) With the switch in Reverse (in position) I get NO power at both Pin #1 Lower Right (wire to motor) and at Pin #3 Upper Right (wire to motor).

Does this suggest the issue is more likely caused by the switch instead of the motor?

The other forum's poster suggested that I do the same test on the two wires at the motor, but I do not know how to access the motor.

Thanks!!

 

[Bearded Cabbage]

I have no idea what the solution could be. But I too have the same problem and I am looking forward to seeing where this thread goes.
Good luck with the fix!

 

[MCObray]

Any luck? My lumbar is stuck in one position, and not working at all.

 

[LittleCaesar]

I'd bet the farm the motor is bad. My switch was bad when I replaced mine two years ago but then the motor went.

There are two connections between the switch and the motor with the wires running in the rear of the seat. Pull one of the connections apart and see if you get 12v when the switch is pressed. If you do, then more than likely the motor is shot.

If you decide to remove the motor and housing, wear gloves for the seat metal housing is sharp.

 

[IBallEngineer]

Update:

I tested by running jump wires from Pin #4 Lower left (power, 12V) to the one of the motor wires (Pin #1 or Pin #2) while the other motor wire was hooked up the ground. Nothing happened.

From a suggestion on another forum, I added jump wires between the switch and the wires coming out of the seat so that I could test the voltage as I operated the switch (4Runner power on).

Pin #4 Lower Left (power, 12V)
Pin #1 Lower Right (wire to motor)
Pin #2 Upper Right (wire to motor)
Pin #3 Upper Left (ground)

Results:
a) At all times, I get 12V on the Pin #4 Lower Left wire.

b) With the switch in forward (out position) I get power (12V) at both Pin #1 Lower Right (wire to motor) and at Pin #2 Upper Right (wire to motor).

c) With the switch in Reverse (in position) I get NO power at both Pin #1 Lower Right (wire to motor) and at Pin #3 Upper Right (wire to motor).

Does this suggest the issue is more likely caused by the switch instead of the motor?

The other forum's poster suggested that I do the same test on the two wires at the motor, but I do not know how to access the motor.

Thanks!!

One thing I've noticed is you haven't confirmed you have a good ground at T3.

Assuming it is good, your test powering T1 and grounding T2 should have operated the motor, reversing these two also should operate the motor. Now if the wires all the way to the motor are good, the motor is bad.

Regarding the switch--

At rest T1,2,and 3 should all be grounded.
Forward position T2 should be 12V, T1 should be ground.
Rear position T1 should be 12V, T2 should be ground.
At no time should both T1 and T2 be 12V.
If any of the above conditions are not met, the switch is bad.

Double check your tests and decide accordingly. Not likely they are both bad, but it is possible. I'll follow to see how you do!

:couch2: