1995 Saturn SL1 reverse/back-up lights & switch

Roger,

I have never had a problem with that circuit, but your troubleshooting logic seems sound and the single wire to the bulbs infers a chassis ground to complete the circuit (make sure the grounds are good and not rusted). That said, I do have some questions though that may help shed some light here:

Are you sure you have the correct fuse? (IMO Haynes is not a very good source to guarantee this is the correct one).

How are you measuring connectivity from the top of the reverse light switch to the "top" of the fuse?

When you measure 12.7V at the "right" terminal of the back up light fuse, what do you read on the left terminal (this assumes the fuse is in the circuit)?

Are there two gear selector driven electrical switches (one for parking/neutral safety interlock and another for the reverse lights) or just one and if so, are you on the correct one?

Are there any other symptoms/non-working electrical systems?

Do the reverse lights flash at all, even for a brief moment when the gear selector is moved through all the gears from park and back? (Safety first - This takes a second person inside the vehicle to see what is actually happening outside.)

What voltage to chassis ground do you measure on the input to the reverse switch when the ignition is switched "on"?

Bob

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....

Bob Shuman wrote: > Roger, >

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

Roger,

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.

Bob