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70 ElCo front signals don't work when headlights are on

5K views 28 replies 10 participants last post by  KevMc 
#1 ·
All signal indicators work fine when the headlights are off but the front signals will not blink when the headlights are on. Dash indicators (sweep dash) blink fine headlights on or off, rear indicators work fine all the time. I have tried several different relays (thanks cool guy at AutoZone). All screws are tight that hold the lamp assembly. Took out the bulbs and rotated them 180 no difference. Hazard lights seem to be struggling to work with the headlights on. Left side was trying to blink, right side no so much.
All worked fine when I got the car, have a new AAW harness up front since I had the clip off.
 
#2 ·
It'll either be a ground problem or a loose wire on the ribbon cable towards the bottom passenger side of the steering column. That loose wire nearly drove me insane a year ago trying to figure out my turn signal problem. I had no problem with my AAW wiring harness other than self-inflicted problems by me.

Rick
 
#5 ·
The pins on the Chinese bulbs aren't as prominent as before and its very easy to put them in wrong. I have found that the bulb itself is often cocked even when installed correctly because the pins don't fully engage the channel. I buy old NOS or German bulbs and have zero problems.

In regards to the OP, with an ohm-meter, make sure the socket housing is grounded correctly to the bumper and the bumper to the frame. I too had the same problem and had to replace the fixture due to excessive corrosion inside the socket preventing a good ground.
 
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#6 ·
On my one owner 70 SS 454 El Camino, I had Turn signal//Parking light issues. Here is how I solved the problem. I started by using a LARGE Alligator Clip: with a long wire attached. Attach the Alligator. Clip to the bulb HOUSING, ( It has the brass looking color, and the indentations for the bulb pins.
Now ground the wire to the bumper. With the clip & wire on the bulb housing and the other end clipped to the bumper lights are OK.
SO,,,,,,,,, I pulled the light housing off of the Camino. Then I soldered a small stranded piece of wire to the " Brass looking bulb housing". The other end of the wire, Drill a small hole in the housing ( drill the hole on top ,,So you do not see the wire). Now a small eyelet crimped to the wire and a small metal screw through the eyelet and attach to the housing.
My problem WAS........... Where the Brass bulb housing is crimped to the lighthousing, Dirt,Debris and standard corrosion,,, The brass was " NOT" grounded very WELL " AT THE CRIMP " to the housing.
New ground wire in place......... All is well,
With the ground wire attached to the top of the housing, ( from the brass to the lamp housing,, You can not see the NEW stranded ground wire.)
Bob
 
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#7 ·
Played with the test light, I have good ground to the bumper and bulb housing. With headlights off both contacts in the housing show good ground, lights on, the test light flashes when touching the upper contact (in the housing socket) but no ground at the other contact. I guess I will try separate ground as suggested above. I'm out of roach clips at the moment.
 
#8 ·
Found a bit more free time...I took one housing out, grounded it back to the bumper and made another ground to the brass bulb housing, same deal, no blink with the headlights on..fine with headlights off.
I do have a ground off the battery to the core support.


Edit, I didn't try with the test light...more to come


Edit again, same deal with the test light.
 
#9 ·
Hook your test light roach clip directly to the neg batt terminal on the batt and test with the headlights on and the right turn signal on. Is your dash indicator and rear turn signal flashing and what are the results of the 2 contact tests?

The ground is supplied through the base of the buld and lamp socket assembly. Ond contact is for parking lights and should give a steady burn on the test light. The other is the turn signal contact and should flash in sync with the rear turn signal.
 
#11 ·
Did this and it did exactly what you said it should, without grounding the housing or the brass socket.

I'm chalking this up to either garbage Chinese bulbs or possibly the socket is worn just enough to cause issues.
Both sides work fine now after putting the bulb in and out three hundred times but now the pass side dash indicator light stays lit with the headlights on.

Where can I get quality bulbs? What I have are Sylvania, stamped China.
 
#10 ·
It sounds like you have a drop in voltage when the headlights are on. Check battery voltage with headlights on and off. Next check voltage to the socket with headlights on and off. Pierce the wire to do this check. Use a straight pin, place a piece of wood behind the wire for back-up when pushing the pin into the wire. Have you tried a solid state flasher ?
 
#12 · (Edited)
Does your fuel gauge work and read correctly?

I don't know where to find "good" bulbs. Phillips is made in Taiwan. I saw some other brand made in Mexico. I've never had an issue with any bulbs, they work or don't when the filament is broken. I don't know where NAPA bulbs are made, but we use lots of them at work without issue.

I think all your issues are ground related. The AAW wire kit only covers half the circuit in the Chevelle. The other half is the ground circuit. If your car was restored, there a good chance that some components are not being grounded correctly. Some times when parts are disassembled and painted then reassembled you won't get a good ground between the components. Ground wires and ground straps are often deleted or ignored. A rusty crust body can have the same issues. Poor ground connections between panels due to corrosion.

The dash indicator lighting with the headlights tells me that the headlights or parking lights are seeking ground when turned on. The test you did with the test light connected to the neg battery tells me the power circuit is ok. It's when you rely on the ground system itself when you have issues.

Let's look at the ground path to the turn-signal housings. The housings are grounded to the bumper. The bumper is grounded through the bumper brackets to the frame. The frame is grounded to the firewall. the firewall is grounded to the engine and the engine is grounded through the alt bracket to through the batt cable. Technically, your engine is isolated from the frame by the rubber engine mounts and the rubber trans mount. The body is isolated from the frame by rubber mounts aswell. So ground straps are installed to connect each section to ground. There is the additional body ground off the battery to the inner fender. Almost all these connections can be crustily corroded, painted and insulated or missing.

I suggest you check and clean all your ground connections to bare metal. This includes the headlight ground wires that screw into the radiator support. Replace any missing ground straps. Engine to the firewall, firewall to the frame. There's a ground wire to your instrument panel and the last picture shows the ground wire for the headlight switch to the instrument panel. If this doesn't do the job, run a self-tapping screw directly into the turn signal housing and a wire to a good solid ground bypassing all the bumper mounts and the rest of the ground path.

When you turn on your headlights the parking lights also come on. There's a good chance that lack of ground to the turn signal housing is causing the dash indicator to light.

If you pull the bulb from the offending housing, the indicator light should go off...I think. If you turn on the signal without a bulb, the indicator should light and possibly not flash if there is not enough current draw to trigger the flasher.

There is no ground wire on the front turn signal housing. It's grounded through the mounting bracket to the bumper. The 2 wires that come into the housing run power in for the park light and turn signal. They come painted up which could insulate the ground path. The screws tighten up on a clip type nut that may also be insulated by paint or corrosion.

Problems started when you removed the front clip, so think about what has happened since then. Repaint? new bushings, Some original ground straps not replaced. Painted bumper brackets and bolts. Anything that could hamper a good ground connection.

This can be frustrating, just go one step at a time and you'll get it.
 

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#13 ·
I really appreciate your homework. I honestly don't recall any ground straps around when I pulled the motor and clip, but I do need to add some. Here's what's odd, I took both housing off the bumper, so they're not grounded now, and the flashers work fine, but the dash indicators stay lit. Put a ground to the housing and they don't work, dash indicators work as should. All this is with headlights burning.
 
#14 ·
Almost sounds like they are grounding THROUGH the headlights. The ground is connected to the headlight power side. So when they are on, they ground through the filaments of the headlights. But when the headlights are on, there is +12v on both ends of the signal bulbs, so nothing happens.
With the headlights turned off, If you unplug all 4 of the headlight bulbs, do the turn signals still work?
 
#16 ·
All signal indicators work fine when the headlights are off but the front signals will not blink when the headlights are on. Dash indicators (sweep dash) blink fine headlights on or off, rear indicators work fine all the time. I have tried several different relays (thanks cool guy at AutoZone). All screws are tight that hold the lamp assembly. Took out the bulbs and rotated them 180 no difference. Hazard lights seem to be struggling to work with the headlights on. Left side was trying to blink, right side no so much.
All worked fine when I got the car, have a new AAW harness up front since I had the clip off.
Just noticed this part of your post and this should not be possible.An 1157 bulb has 2 small nibs or tits on the side of the bulbs that locate them in the lamp socket.One nib or tit sits a lot lower than the one on the opposite side so if both nibs are equal the bulbs aren't 1157's.If the nibs are offset then there may be a problem with your bulb sockets being worn out or corroded.
 
#18 ·
I've added a big ground strap to the frame and made one from 10ga wire to the inside of the fender, both directly off the neg post to clean metal., haven't really made any progress, but it does look like the signals are just barely trying to blink. Will be adding one to the firewall and another off the frame to sheetmetal in the rear somewhere.
 
#20 ·
Rear lights work as should under all conditions, brake, signal and hazzard. Still the same issue on front signals.

Added firewall ground, off the battery with 10 ga wire, and another ground off the frame in the back to the sheetmetal with a short 4ga battery cable. I put new bulbs in the front signals just because..


So, currently (pun) I have a fat ground strap off the neg post to the frame. I have a 8 ga wire to the core support and a 10 ga to the fender sheetmetal, and another 10 ga to the firewall. These all branch off the neg post of the battery. Also 4ga from rear frame to the body. No paint under any connections.

This things more grounded that a flight full of coronavirus.
 
#21 ·
There's not much left. Still suspect a ground path issue to the light housing. With the lens off the turn signal housing run a wire from the neg of the battery and turn on the signal and touch the ground wire to the exposed bulb copper base. If it works, you know you still have a ground path issue.

Is your dash properly grounded and I forgot how the indicator lights were grounded, either by individual wires or directly to the grounded dash. For the dome light to work by turning the switch, the h/l switch needs to be grounded to the instrument panel. for the wipers to work the wiper switch needs to be grounded to the dash and then the dash is grounded.

We can check the power coming out of the turn signal switch under the dash on the column there is a connector, see attachment. Check it with a test light, not led type, and if the front signal leads flash there you may have a connector issue or wire issue in the circuit to the lights. The circuit runs through the bulkhead connector to the forward light harness. You can leave the connector connected and push the probe up the wire into the connector. If the probe is too thick, make a crutch with a paperclip and insert it in the wire end of the clip into the connector. Poor contacts in the bulkhead connector can cause issues. If you're a big guy, pulling the front seat makes this easier.

Light blue wire = left front turn
Dark blue = right front turn
White is power from stoplight switch
Green right rear turn
Yellow = left rear turn
pink w/ black tracer = key buzzer
black next to the pink w blk tracer = key buzzer
Black is the horn, It will show a ground signal when tested with an ohmmeter, No power runs here.
Brown is the signal lead from the 4 way flasher
 

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#22 ·
I had an issue with my front parking lights not working when my headlights were on and I spent a long, frustrating time trying to find that damn gremlin in my wiring. All my grounds are good too. I ended up using a short piece of wire with connectors in each end. I screwed one into the housing with a sheet metal screw and connected the other end to the screw in the bumper. I realize that it's not factory correct, but it got rid of that gremlin. Sorry that the pic isn't that good. Hope this helps.
 

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#25 ·
Just a quick and simple check; With the bulb in, pull back on the harness and let it snap back into the socket. It should be easy to pull and snap back. Any resistance means there's corrosion or dirt behind the terminals. As mentioned above in post #5, I ended up replacing the fixture. It was worth buying new rather than spending so much of my time trying to repair the old one without success.
 
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#28 ·
The ground wire needs to go to the ground side of the housing. The 2 wires going into the light socket, 1 is for the power for the park lights, it should light up the taller element in the bulb. The other is for the turn signal and it lights the shorter filament in the bulb. When I say shorter, that looking at trhe bulb from the side, not the length of the filament.

If the housing wasn't connected to the grounded body of the car, say you had it on a bench, you would need 3 wires to get it to function as a park lt and turn signal. One ground to the metal base, and 1 for park and one for turn.

Keep at it, you'll get it.

What might be messing with you, the turn lamp is made from 2 pieces of stamped steel that are crimped together. You might not be getting a good ground between the 2 stamped pieces. That's why I suggested pulling the lens and using a wire connected to the neg lead and touch the other end to the brass of the bulb directly. No chance of being a ground interruption in this test.
 
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