1995 Saturn SL1 reverse/back-up lights & switch - resolved thanks

Discussion in 'Saturn S-series' started by Roger, Nov 20, 2008.

  1. Roger

    Roger Guest

    Thanks Bob & Folks

    My problem with the reverse/back-up lights switch is resolved. I was
    examining the wrong switch to be honest. There are two sensors that
    appear similar on my manual transaxle case. One sensor (2 wire) is near
    the back, which I saw when looking from underneath the car. The other
    sensor (also 2 wire) I noticed later is on the top of the transaxle near
    the dip stick, but somewhat hidden from view by the components over it.
    The tests I mentioned below in previous posts were on the lower sensor
    underneath the car. Saturn tells me that this is actually a speed
    sensor..... I found the other sensor later and it is indeed the backup
    lamp switch. I repeated the tests on it and everything measured as
    expected. Also shorting this switch did keep the lamps on with the
    ignition on. I see no parking/neutral safety interlock switch though.

    I did buy a replacement backup lamp switch from Saturn ($14) and
    replaced it myself.... bingo.... backup lamps work correctly now.

    Cheers, Roger

    1995 Saturn SL1 reverse/back-up lights & switch

    Car: 1995 Saturn SL1 SOHC.

    Symptom: Both reverse/back-up lights do not turn on when in reverse gear.

    My troubleshooting: From reading my Haynes manual.... I located the
    Back-up Light Switch on top of the manual transaxle.
    1. The Back-up Light fuse is good.
    2. Bulbs test fine.
    3. There is circuit continuity between Back-up Light fuse (at front
    engine fuse box) and lamps and also from the Back-up Light fuse and the
    right contact of the switch plug (view w/ clip @ top).
    4. With ignition ON (engine not running) I read 12.7V at the right
    terminal of the Back-up Light fuse. In this state I read only 60mV at
    the right contact of the switch plug and the lamp terminal with the bulb
    5. Wires and Wire-harness look in good shape.

    From the circuit diagram I should be reading Voltage on the battery
    side of the switch connector, then also on the ground side of the switch
    when in reverse if the switch is good. Right now it seems that I cannot
    conclude that the switch is bad by testing it properly. This looks to be
    a simple bulb circuit, power is switched ON/OFF by the transmission
    (manual) Backup switch alone.... am I correct?

    *from a suggestion on another forum....
    Is this a feasible way to troubleshoot this circuit? Because I'm getting
    no light but have continuity, I wonder there is some other component in
    the circuit.....
    With ignition key OFF, I unplugged the 2-wire connector from the switch,
    closed (short w/ wire) the circuit on both terminals of the
    connector.... turned ON ignition key.... still no light, also ran
    engine.... still no light.

    The bulbs are type 1157. These have two filaments/terminals, but I
    notice that the sockets only have one positive terminal, I assume ground
    is in a connection to the base body. The sockets are keyed, nothing
    looks physically broken.

    It looks that if I'd replace the switch the problem would not be solved.

    Any thoughts? Thanks very much for your assistance, much appreciated.
    Cheers, Roger

    Thanks very much for your assistance, much appreciated.
    Cheers, Roger

    Hi Bob

    Thank you very much for your reply, much appreciated. Sorry I did not
    reply sooner, I had to find some time to look at the circuit again. I'll
    answer your questions below....

    The socket single contact looks fine, no corrosion, but I'm looking for
    the 2nd contact (ground), it may be recessed in the sleeve or the 2 key
    notches may act as this terminal. I looked on the net for the 1157 bulb
    specs... found them but no specific details confirming the common ground
    electrical connection. All the bulb sockets are lined with a cream
    inside, (original).

    Yes, 10A fuse, also labeled as such on the fusebox cover. Fuse is good.

    I removed the switch plug/connector and inserted a 22 AWG wire into each
    terminal of this plug.... one at a time .... used this as one circuit
    node and the other at the terminal socket for the fuse in the fusebox
    (fuse out), and checked electrical continuity.

    No I had the fuse out (open circuit), the left terminal reads 0V.....
    ignition ON (engine not running).
    Only one switch. On the top/back end of the manual transaxle.... also
    referenced in Haynes manual.

    No other electrical problems/symptoms.

    No flash or light at all. I opened the rear lamp case on each side,
    removed the backup lamp socket, and rested it with the bulb in on the
    case peeking out along the side of the car so that I could notice any
    light as I watched in the mirrors when shifting to reverse.
    Only about 60mV, not zero....

    I examined both 1157 bulb's sockets again. They are coated with a
    anti-corrosion cream on the inside. I also notice on both left and right
    sockets that the ground terminal, a flat metal prong is recessed
    somewhat, not touching the brass cylinder case of the bulb. It is also
    situated higher up at the point where the brass cylinder case ends and
    the glass of the bulb begins. There definitely is no electrical contact
    here on both Lt & Rt sockets. It appears that this may have been the
    design during manufacture. Strange then were exactly is the ground
    terminal? I also sprayed contact cleaner into both sockets. The
    terminals are free of oxidation.

    Thanks, Roger

    Author: Bob Shuman
    Date: Sep 3, 2008 08:11

    The 1157 is a two filament, 3 conductor/contact bulb that has been
    around for many, many years. It is usually used for a combined turn
    indicator/brake light function. Are you sure this is the correct bulb
    number and does it have 3 contacts (two soldered dimple contacts on the
    base and a brass base for the common/shared ground)? I would have
    expected you would have found a two contact, single filament 1156 bulb
    for the back up lights. BTW, The anti-corrosion grease used in the
    socket is normal, but the contacts from the socket should make good
    physical/electrical connection with all 3 of the bulb's contacts. That
    all said, it doesn't seem likely that both contacts in both sockets have
    connectivity issues and this is why I had suggested that you make sure
    the grounds are there to both sockets (I assumed they may share a common
    lead and physical connection to the chassis).

    I'd suggest that you measure the resistance from the ground pin of the
    socket to the vehicle chassis. You should see roughly an ohm or less of
    resistance from both of these contacts ion the sockets.

    Also, please re-verify you are looking at the right sockets and have the
    correct bulb number. Is it possible that a previous owner put in 2 of
    the wrong bulbs? How many contacts are in the socket and do they match
    the bulb?

    I have other questions as well on the reverse light gear selector switch
    too. I really would expect there to be two switches: one for the reverse
    lights and another for the starter safety interlock (park/neutral)
    switch. I'd expect these to both go "hot" (12V) as soon as the ignition
    gets switched on. If there is truly just one switch, then I'd also
    expect to see more than one output from that switch since it needs to
    validate that the vehicle is in either park or neutral to start as well
    as light the reverse lights when in reverse. If you can get a copy of
    the schematic and trace the circuit from the fuse box where you see the
    12V through to one of the reverse bulbs that would be the best way to
    troubleshoot this issue.

    At this point there is too much apparently conflicting information in
    what you have shared thus far for me to try to troubleshoot this remotely.

    Roger, Nov 20, 2008
  2. Roger

    Bob Shuman Guest


    Congratulations on the fix and saving yourself a lot of $ by diagnosing and
    fixing it yourself! Thanks for closing out the thread and letting us know
    how it worked out.

    Bob Shuman, Nov 21, 2008
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