Inner Rear Turn Signal Bulbs Won't Work

[2seater]

I realized the inner turn signal bulbs do not work on my car. I thought it rather odd that the high filament for the inner left and right turn signals would burn out at the same time, but stranger things have happened. The outer two bulbs on each side work fine as well as the flash rate. All tailight bulbs also work correctly. New bulbs made no difference and the originals test good in any case. After consulting the FSM, I see the outer two on each side are controlled through the turn signal flasher in the dash. The third bulb (inner) on each side is operated from a micro-relay in the trunk activated from the turn signal wire for the outer bulbs. Checked the relays on the bench, all good, and can hear/feel them work when installed. Wiring continuity from the relay sockets to the bulb contacts and also ground check out good.

The one item that does appear to be failing is the available voltage to the relays in the trunk. I had a bit over eleven volts to start with, voltmeter load only. I thought the battery was running down due to the other things I had been doing to get the car ready to put away for the winter, so attached a charger. The 20A fuse that feeds the relays is good also. While testing the relay sockets, I noted the voltage was showing a steady drop, down to 8.5 volts at the end with the battery @ 14v. I don't "think" it is a ground issue as the voltage at the #3 terminal for both relays read the same using three different ground points in the trunk area. Apparently something is amiss with the power feed, at least that is my conjecture. Additionally, I also seem to have lost the trunk light, even though the bulb is also good. Checking with a voltmeter to the trunk light socket also shows some voltage but I believe it doesn't hold up with any real load. I am looking for suggestions as to where to look. Is this one of the infamous connections under the seats? Any thoughts appreciated.

[Guest Mc_Reatta]

How well do your power door locks operate?

Does your trunk unlatch when you use the key in the lock? (Not the remote or glove box switch)

They and the inner turn signal bulbs as well as the trunk light all get power thru splice S311 (orange wires) under the driver's seat.

If your not getting good voltage at those locations I'd suspect that splice.

[2seater]

Mc, many thanks. The rear trunk release is also non-functional. I don't know about the door remotes as the batteries are dead and won't be replaced until spring, but, the door locks have been acting oddly. The lock/unlock with the trans. shifter has been getting erratic. I guess this repair will have to wait until spring as well, so it will be added to the list. Must get it into storage before it snows again.

[Guest Mc_Reatta]

Sure sounds like a splice repair job will be needed in the Spring.

[2seater]

I don't know if this confirms or is a different issue, but the drivers door lights (red/white at bottom), don't work either. Bulbs tested good. All other interior lights work as they should. It's sort of funny, but in over twenty years of ownership, I've had almost no electrical issues, many of which have been reported over the years. I never joined in to help as I had precious little experience, but it looks like the shoe is now on the other foot. This has been a summer only car for over two decades, and never had any real moisture issues on the interior, so it will be interesting to see what the problem is. It's now sleeping fifteen miles away. Thanks for the help as always.

[Guest Mc_Reatta]

Well according to the FSM, power to those lights in the door is carried on an orange wire that just happens to go through a certain splice S311 under the driver's seat.

Who would've guessed it?

Oh I guess you did.

Hope it has a good hibernation.

[Barney Eaton]

I may be misreading your question, but on the rear there are a total of 12 double filament bulbs plus the single 194 marker on each end.

Disregarding the 194 end marker, there are then 3 bulbs on each side that are stop and turn signals. The middle 6 bulbs are only running/parking lights. The confusing part is that all 12 bulbs are double filament bulbs which would lead you to believe they should flash with the blinkers or light when the brake pedal is pushed.

I have often wondered why the Reatta has double filament bulbs in those 6 middle positions..... maybe they had some plan that did not work out or maybe it was cheaper to just use all the same sockets and bulbs across the assembly.

I would be fairly easy to make the middle lamps work with the brake lamps, but maybe it would blind the driver behind you.

[drtidmore]

The middle 6 bulbs are only running/parking lights. The confusing part is that all 12 bulbs are double filament bulbs which would lead you to believe they should flash with the blinkers or light when the brake pedal is pushed.

I have often wondered why the Reatta has double filament bulbs in those 6 middle positions..... maybe they had some plan that did not work out or maybe it was cheaper to just use all the same sockets and bulbs across the assembly.

Barney,

I think the most likely reason for the use of the same dual filament bulb across the entire tail light was to ensure uniformity of brightness in taillight mode. As GM did not include the wire for the second filament in the center 6 positions, they wound up with different sockets for the inner vs outer position so not likely much if any cost savings even though the actual mechanicals of the socket were the same.

As to why only the outer 3 bulbs on each side vs all six for turn/brake signal, most likely answer, the amount of current that doing such would involve. Those 2057 bulbs are hungry beasts on the high output filament (2.1amps per bulb). Granted when the brake lights are active (i.e. 6 each 2057 bulbs running) is the SAME as using all 6 on either side for turn signals, but having all 12 running for brake lights would have required double the output from the turn/hazard/stop module (88/89 models)and a redesign of an existing expensive electronic component. Always remember that the Reatta inherited a LOT from the existing mid-80s Riviera design in order to keep engineering and manufacturing costs levels down. Even with the 90/91 changes, those were totally inherited from the Riviera once again.

FYI, making those center 6 bulbs high output filaments active is a recipe for problems as the factory wiring is too small the handle the additional current as is the turn/hazard/stop module on the 88/89 models years. Even though the 90/91 models returned to using a mechanical "can" flasher, it would likely not be up to the doubling of current nor would the brake light switch. We are talking about a significant amount of amperage (all 12 running on high output is 25.2 amps).

As a DIY mod, adding relays to power an alternative tail bulb setup IS totally possible as long as the power to those bulbs is run separate from the factory wiring. FYI, doing this will require mod'ng the burned out bulb indication feature (I did this for the opposite reason when switching over to LEDs across the rear)

Of course, the above is just my opinion, but there are sound engineering factors that support what I have stated.

[2seater]

Mc, I didn't really guess, but I thought perhaps it was another clue as to the malady. It sounds like you confirmed my additional info.

I am not sure GM was concerned about brightness of twelve brake light bulbs all at once, but possibly so at that time. If you follow a Chrysler model with the full width LED tailights (and probably others) today, they are WAY brighter than anything we might be capable of. Too bright IMHO. My best guess as to why two lights on each side operate in a conventional manner (from the front) is as conjectured, it probably matches the Riviera rear lighting. The cost to add two relays at the rear, one each for the third bulb on each side would seem to be relatively costly for what gain? I haven't looked at the power capacity feeding those relays, but I would guess it could certainly fire more than one bulb? Perhaps they wanted to maintain a clear seperation between the turn signals? Probably never know what they were thinking? It would be relatively simple to add a heavier power wire to the rear and use a higher capacity relay to power more bulbs but again IMHO, movement draws the eye more effectively, such as the sequencing turn signals. Pesonally I would like to see four bulbs on each side, but as drtidmore pointed out to me, the sequencing must take place in the time for a single normal flash, so the number of bulbs in the sequence will make a difference in the appearance. A small amount of amperage (about .2A each on high) could be be saved by installing all 1034 bulbs in the rear but I believe the rated life is less and the savings doesn't even add up to 1/2 of one additional bulb even with four on each side.

[drtidmore]

As the issue of brightness came up, here is a pic with two of the LEDs installed flanked on both sides by the 2057 incandescent. As you can see there is a massive difference in brightness and this is NOT the high output levels. I have asked numerous people that have followed me at night if the brightness is TOO much in taillight, turn or brake modes and no one has indicated so. FYI, the yellow appearance in the pic is an artifact of my camera. The actual color is pure red. The exposure needed to show the other bulbs simply caused the LEDs to be overexposed.

Here is a short clip of the sequential turn signal in action. At this point all the bulbs are LEDs. The clicking you hear in the video is the one of the relays that I added to preclude sequencing during hazard as well as the single sequence that would happen with each brake pedal application otherwise. I used diode protected 30amp auto relays, but have since purchased a bunch of 12V reed relays that are silent and since this application simply grounds an inhibit wire on each sequencing module, there are NO amps being drawn via the relay contacts.

http://www.youtube.com/watch?v=QQLeh0XS7k8&feature=youtu.be

Edited December 2, 2013 by drtidmore (see edit history)

[2seater]

Very nice. I suspect the pure red light of the LED does help preserve night vision even though quite bright.

[2seater]

I resurrected my old thread to post the results and add an observation.

The giant orange splice of eleven wires was indeed bad. Not just corroded but two wires actually broken. One other splice, three light blue to three light blue was bad also. All others proved to be good, as well as all splices under the passengers seat. All operations are now restored. Many thanks for the help.

The observation is the same as the '89 I was trying to resurrect. There was a lot of water under the carpet on the drivers side only, passengers side completely dry. This one actually had what I would term standing water. The padding was so saturated there was visible liquid on the top. Both cars were garage kept for nine months prior to pulling the carpet, so it appears the water infiltration does not evaporate over a considerable period of time. Neither car had evidence of leaks at the rear window, the hatches behind the seat were completely dry and no telltale tracks were visible. My guess is the poor water control due to lack of drip rails allows more water in than suspected and while the top of the carpeting does dry to the touch, what gets underneath, stays there and builds up over time. Just a guess.