Electrical Gremlins

[Natural Citizen]

I finally got that wiring harness installed the other day.

I've got all of the gremlins worked out except for one.

Here's what I have going on.

I have the front turn signals/running lights and then I also have the side front turn signals.

On the left side, the side front signal works fine.

And the left front signal/running light works.

Except the left front signal doesn't blink when the running lights are on. It stays lit solid.

Only thing I can think of its a bad ground in the socket. But the socket is pretty clean.

 

[BULLDOG]

First thing I would check would be a short between the running lights and that socket. Of course, with everything being driven by computers and microcontrollers now days, a bad ground can cause problems that don't even make sense.

 

[HenryBHough]

I finally got that wiring harness installed the other day.

I've got all of the gremlins worked out except for one.

Here's what I have going on.

I have the front turn signals/running lights and then I also have the side front turn signals.

On the left side, the side front signal works fine.

And the left front signal/running light works.

Except the left front signal doesn't blink when the running lights are on. It stays lit solid.

Only thing I can think of its a bad ground in the socket. But the socket is pretty clean.

If the light is on at all it's not a bad ground. The ground is common for both filaments in a lamp (bulb) which serves for both running and signal lighting. First check to see that the right lamp is in the socket. It may be a single-filament lamp only with the center contact wide enough to touch both the two contacts that are part of the socket. Or there may be a short circuit in the socket itself. Also possible the lamp has an internal short circuit. An Ohmeter can tell you but if you don't have one try swapping the lamps between the left and right sockets - see if the problem "follows" the lamp or stays with the socket. If it follows the lamp get a proper replacement.

To do much more will require a voltmeter with one lead on a good ground and the other....now here's a trick. Remove the lamp. Stick a common pin through each of the 2 wires going to the socket (if there's a third wire it should be a ground - usually there are only two.) With all lights off, apply the ungrounded (other) lead of the meter to a common pin stuck through the insulation on the wires going to the socket - one at a time. With the running lights and signals turned off check for voltage between each of the pins and the ground. Then turn on the running lights and check both wires again. Only one should have continuous voltage. The other should have none. Then swap the lead to the other wire and turn on the signal. One wire should have a pulsing voltage; the other should have none.

If you have voltage on both wires with only one of the two sources (running lights/signals) active then you have a crossover short. It could be a bad socket or it could be upstream. Myself, I'd cut one of the wires and try the test again. If the problem goes away then you have a bad socket. Replace the entire socket. If the problem does not go away you have a major project. The problem may be anywhere in the harness but I'd be concerned that something is fried in the light control computer.

Good luck!

 

[Natural Citizen]

If the light is on at all it's not a bad ground. The ground is common for both filaments in a lamp (bulb) which serves for both running and signal lighting. First check to see that the right lamp is in the socket. It may be a single-filament lamp only with the center contact wide enough to touch both the two contacts that are part of the socket. Or there may be a short circuit in the socket itself. Also possible the lamp has an internal short circuit. An Ohmeter can tell you but if you don't have one try swapping the lamps between the left and right sockets - see if the problem "follows" the lamp or stays with the socket. If it follows the lamp get a proper replacement.

To do much more will require a voltmeter with one lead on a good ground and the other....now here's a trick. Remove the lamp. Stick a common pin through each of the 2 wires going to the socket (if there's a third wire it should be a ground - usually there are only two.) With all lights off, apply the ungrounded (other) lead of the meter to a common pin stuck through the insulation on the wires going to the socket - one at a time. With the running lights and signals turned off check for voltage between each of the pins and the ground. Then turn on the running lights and check both wires again. Only one should have continuous voltage. The other should have none. Then swap the lead to the other wire and turn on the signal. One wire should have a pulsing voltage; the other should have none.

If you have voltage on both wires with only one of the two sources (running lights/signals) active then you have a crossover short. It could be a bad socket or it could be upstream. Myself, I'd cut one of the wires and try the test again. If the problem goes away then you have a bad socket. Replace the entire socket. If the problem does not go away you have a major project. The problem may be anywhere in the harness but I'd be concerned that something is fried in the light control computer.

Good luck!

I never even thought of sticking pins through the wires, Henry. That's a darned good idea. Thanks. I'll go out tomorrow and try it that way. I've got the tools to do it.

The bulbs are right. They're also new, I went to NAPA and picked them up today. They're what the car calls for, the 2057NA.

I do already have two new sockets. The new sockets I have are double contact sockets. I didn't install them when I replaced the harness because the ones that were on there ''looked okay'', heheh.

But, now that you mention it, I didn't even think to check if the socket with the problem is a single contact socket. It might be a single contact socket on the one that's on the car now with a double contact bulb.

Good info, thanks, I appreciate that.

 

[Natural Citizen]

First thing I would check would be a short between the running lights and that socket. Of course, with everything being driven by computers and microcontrollers now days, a bad ground can cause problems that don't even make sense.

I'm gonna try Henry's checks tomorrow and see if that solves it. I hope it's not a short, I don't feel like snaking that thing back out, it took six hours to remove the old one and get the new on routed all through everything.

 

[HenryBHough]

I'm gonna try Henry's checks tomorrow and see if that solves it. I hope it's not a short, I don't feel like snaking that thing back out, it took six hours to remove the old one and get the new on routed all through everything.

I think it unlikely but do make sure it's not a situation where they use separate lamps and separate sockets for running/signal. I don't recall your mentioning what breed of vehicle. Beware systems with positive grounds (many european models and the occasional oddity like some of the AMC Eagles that were secretly Renaults). In those the wires are very small gauge and every thing goes back to a central computer separately.

I used to nick insulation to get a probe onto the conductor but got tired of having to tape it over. Removing the pin pretty much self-seals the hole.

I'm hoping the "calls for" statement means read from the owner's manual not a chart in a parts store or off the lamp that was in the socket.

 

[Natural Citizen]

I think it unlikely but do make sure it's not a situation where they use separate lamps and separate sockets for running/signal. I don't recall your mentioning what breed of vehicle. Beware systems with positive grounds (many european models and the occasional oddity like some of the AMC Eagles that were secretly Renaults). In those the wires are very small gauge and every thing goes back to a central computer separately.

I used to nick insulation to get a probe onto the conductor but got tired of having to tape it over. Removing the pin pretty much self-seals the hole.

I'm hoping the "calls for" statement means read from the owner's manual not a chart in a parts store or off the lamp that was in the socket.

Oh, no, I go by the manual that came with the car. It has a page that says which specific bulbs to use.

It's my old Corvette. It's thirty years old. So just the single socket for the dual filament bulb that works both the running light and the blinker.

But those sockets come in single contact and double contact. And when I put it together I don't know if I installed a single contact socket or a double contact socket. You know how sometimes you just grab one off the wall? Well, I do anyway. That one I did put a new "old" socket on that I had. It might be the wrong one.

The whole reason I bought that car was to have something to tinker around with in my spare time. I didn't even really need to replace the harness, I just did it because it was the age of the car.

Hopefully that's it. If not, I'll try your checks.

 

[HenryBHough]

I think it unlikely but do make sure it's not a situation where they use separate lamps and separate sockets for running/signal. I don't recall your mentioning what breed of vehicle. Beware systems with positive grounds (many european models and the occasional oddity like some of the AMC Eagles that were secretly Renaults). In those the wires are very small gauge and every thing goes back to a central computer separately.

I used to nick insulation to get a probe onto the conductor but got tired of having to tape it over. Removing the pin pretty much self-seals the hole.

I'm hoping the "calls for" statement means read from the owner's manual not a chart in a parts store or off the lamp that was in the socket.

Oh, no, I go by the manual that came with the car. It has a page that says which specific bulbs to use.

It's my old Corvette. It's thirty years old. So just the single socket for the dual filament bulb that works both the running light and the blinker.

But those sockets come in single contact and double contact. And when I put it together I don't know if I installed a single contact socket or a double contact socket. You know how sometimes you just grab one off the wall? Well, I do anyway.

The whole reason I bought that car was to have something to tinker around with in my spare time. I didn't even really need to replace the harness, I just did it because it was the age of the car.

Hopefully that's it. If not, I'll try your checks.

I DO hope you saved the old harness!

On the plus side, with a 30 year old Corvette you likely don't have any computers to worry about. I'm not familiar with that model but it is of a vintage where the lighting control may involve "K-logic" which is to say a flock of plug-in relays. Stuck contacts can cause strange things. It's something I'd look into before putting a lot of effort into tracing wires.

 

[fncceo]

 

[Damaged Eagle]

Try switching the left front bulb with the right front bulb and see if the problem moves.

If it does > Bad bulb

*****SMILE*****

 

[Natural Citizen]

I DO hope you saved the old harness!

On the plus side, with a 30 year old Corvette you likely don't have any computers to worry about. I'm not familiar with that model but it is of a vintage where the lighting control may involve "K-logic" which is to say a flock of plug-in relays. Stuck contacts can cause strange things. It's something I'd look into before putting a lot of effort into tracing wires.

It was a bad ground in the socket itself, Henry.

I just came in from replacing the socket. Works now. Ha! Victory!

But yeah, I kept the old harness until I was sure all the electrical gremlins were worked out. There's still a few other pigtails I can steal off it and stash in a drawer in the garage in case I ever need one. Then I'll salvage and wrap up the old wire. May as well, it's in good shape. I might even steal some loom off it and fill in a few places under the hood where it could use a little more, since the loom is good, too.

Anyway. Thanks for chiming in. I learned something new with regard to using the pins. That'll definitely come in handy in the future.

 

[Natural Citizen]

I actually tried that initially, believe it or not. Heh heh.