Page updated on 06-21-2018

86 Pontiac Bonneville electrical issue

11-25-2006, 09:57 PM
I have an 86 bonneville in amazingly good condition --- everything works! Well, almost --- when it rains the left turn indicator malfunctions and rarely the drivers side window stops working but as soon as it dries out everything is all good again.

I don't have a lot of experience on autos but I'm willing to try --- I know DC circuits and have a multimeter.

11-26-2006, 11:11 AM
I don't think your Bonny is classified as a Classic so this thread has been moved to the Bonneville forum.

11-26-2006, 02:25 PM
Check for 12v at the lamps that are inop, then check for grounds in the same circuit. You can get a basic diagram at, just basic circuit tracing here no quick fix.

11-27-2006, 11:23 PM
Max --- thanks for the advice about the wiring diagrams on autozone, I had no idea you could get detailed circuit info like that for free.

I measured the voltage at the light and its too low to light the bulb, so bulb probably isn't the problem. If i'm reading all this stuff correctly, then the thing that actually flashes the turn indicators on and off is a round canister-like thing on the lower, right corner of the fuse block. Presumable, if this thing is getting the right voltage then this is where the problem is and it needs to be replaced --- the other possibility is that the turn-flasher isn't getting the right power and the issue is electrically upstream from there.

I got half a meter of snow all over the Bonny and it's arctic outflow conditions right now and minus 8C outside so I'm not going anywhere til we get our normal warm and wet weather back and the snow melts and I can get back at this.

Umm, anybody have any idea roughly how much a new turn-flasher is?

Am I doing this right?

11-28-2006, 08:54 AM
I would not rule out a flaky electrical socket for the left turn signal lamps or associated wiring. If the right side turn signal is working correctly then it is probably not a bad turn signal flasher unit. Another possibility is a bad contact in the multifunction/turn signal switch.

Also, to clarify are the front and rear left turn signals the problem or is it just the indicator (idiot light) at the Instrument Panel Cluster?

11-28-2006, 11:25 AM
It's a strange one --- it's only when it's wet out, the problem happens and when it dries out it goes away completely. The indicator inside the vehicle for the left turn doesn't flash when you activate the left turn indicator, it just stays lit but very dimly --- the actual left turn indicator lights on the exterior of the car, front and back don't even light up dimly, they just stay off completely. Right turn is fine --- it always works when activated, both the idiot light and exterior flashers.

Sometimes, if you turn the wind-shield wipers on and off, it will make the left turn work again, but only sometimes.

11-28-2006, 03:10 PM
Starting to sound like the signal switch but confirm your socket grounds, flasher would disable both sidea as Bnaylor stated.

12-22-2006, 10:43 AM
In case anybody is interested, the problem with the flashers turned to from too low a voltage level. The old battery crapped out entirely and I got another one and instantly, all the little electrical system idiosyncracies vanished.
Good thing I decided to wait til I got another battery before I started doing brain surgery on the old girl.

04-22-2007, 01:55 AM
Well, the problem is back again, despite the new battery and now it doesn't go away when it dries out. Another thing I noticed is that the idiot light stays lit all the time, but is so dim that you can only see it at night. When I try to turn the left-turn-indicator on, the idiot light comes on and just stays brightly lit without flashing, and there's no clicking noise. Right turn indicator works fine as always. I located what I think is the thing that makes the lights flash, it's in the fuse panel and is cylindrical --- is this the thing I need to replace, assuming this is what's causing th problem? Do they even make these things any more? It's a 20 year old car!

auto trainy
04-22-2007, 05:17 PM
If I remember correctly there are two flashers,one at the fuse panel and another on or near the stearing post,turn the emergency flashers on to see whitch one works and while its working check all your lights to see if there are any out.Good Luck

04-22-2007, 06:23 PM
If I remember correctly there are two flashers,one at the fuse panel and another on or near the stearing post,turn the emergency flashers on to see whitch one works and while its working check all your lights to see if there are any out.Good Luck

With the emergency flashers turned on,

-Both left & right, dash indicator lights(idiot lights) flash and I hear a clicking noise.
-Rear: all lights flash
-Front-right: both flash (front-main & front-side)
-Front-left: front-main, visible-from-front remains off, but the smaller, front-side light flashes.

I might not have noticed this before, but when I activate the left-turn indicator, the rear, left-turn indicator light (which is supposed to flash) comes on and simply stays on, as does the smaller, visible-only-from-the-side front, left-turn-light. The main, front, visible-only-from-the-front, left turn light, simply does not come on at all.

04-22-2007, 07:18 PM
Seeing as how it's not raining outside for a change, I thought I'd try working on it.
I unscrewed the light panel, removed the bulbs and hooked them up directly to the battery - they work, so it's not a bulb problem. I went to measure the voltage going to the turn-indicator light sockets but the battery in my multimeter is dead, so I tried the turn indicator one last time before buttoning it back up, and it worked (left turn indicator flashed properly)! I screwed in the first panel holding in the bottom lights, tried it again, and it didn't work, so I took it back off, and made sure the wires weren't being bunched up and put the lower panel back, tried it, and now it worked again. So I put it all back together and now it works.
When I get another battery for my multi, I'll try some things, but does anybody know what happens when a turn indicator bulb goes? Does it make the turn indicator stop flashing? If so, then I think for sure the problem is bad contacts on the bulb/bulb-socket. If not, I still don't know. In any case, it works (for now).

Add your comment to this topic!