Help Requested - 1991 Astro Turn Signals

Hello, I am having difficulties with the left turn signal on my 1991 4.3 Astro RWD. It has about 150k miles. As I realize there is more than one potential cause for such as broad issue (turn signal not working), I will try to provide as many details as possible.

I first starting having issues about a month and a half ago. The left turn signal started having intermittent issues. It would have difficulties for about a day, then work without problems for several more, or even "fix" itself during a single commute.

Now, it appears to have finally ceased functioning all together. The right signal works fine (far as I am aware). However, when I turn the left signal on, the light on the dash goes on, but does not blink nor make any sound. Earlier today, I wanted to see how it look from the outside. Neither the rear nor front driver's side/left signals blink function. No blinking or anything. Furthermore, I tried my emergency flashers - the right rear turn signal blinked as it should, but not the left one.

I have to admit, I am not quite sure what the issue is. If it were a bulb, I do not see why both the front and rear signals would not work. I also thought (and I could most definitely be wrong on this), after doing some research online (not always the best source - I know!) that if the turn signal flasher were faulty, nothing would be working - no lights on the dash, no right signal, etc.

Thanks so much for any guidance and please let me know if need to elaborate more.

Sounds like you may have a break or corrosion in the left turn signal wiring somewhere. You would need to look at schematics. You need to verify if any of those bulbs wor at all with the turn switch, hazards, running lights, or brake switch. Use a buddy. Guessing the right side works is not good enough.

Thanks for the response. I tried some more testing and received some very peculiar results.

My right side works just fine. No issues. The left side, on the other hand, is mostly dead. When I apply the brake, the left light does not come on. As noted, the left turn signal also produces no light. However, the light DOES come on when I have my headlights on. The front turn signal does not work either. However, when I turn my emergency flashers on, all lights except the left rear one work.

I would really appreciate any help, it seems like a strange combination of functional and non-functional to me. Thanks.

Hmm, that is quite weird. I'd pick up a cheap Haynes manual if you don't have one. There are schematics in the back. It'd be nice to see where the headlight intersects with the left turn signal.

Another question, both left turn lights turn on with the headlight? Are the turn signals 2 filament, as in, One bulb with a low (parking light) & high (for signaling) setup? If it has the dual filament, can you tell which one is lighting with the headlights? low or high turn?
I hope I can express myself well enough...
I apologize for not replying earlier, but I was setback with work.

Thank you so much for the reply; I am sorry that I neglected to respond sooner. As it turns out, the reason for this strange combination of working and non-working lights and signals was due to the fact that I had two distinct issues - my turn signal flasher was bad, and one of my rear lights is dead. I was able to fix the turn signal, so now both front signals work; however, I have encountered another road block with repairing the rear light.

To my understanding, one needs to open the van's rear door to remove the taillight fixture to access the bulb. The problem is my rear door will not open (no handle on the inside either). The handle just feels loose; it is fully manual, not electric. How would one approach troubleshooting this problem?

Again, sorry for my extremely late response. I really do appreciate the response, and any help I might receive for this question.

Thanks.