Blowing Turn Signal Fuse
 

My car developed a fast left turn signal about a week ago. The parking light is fine, but as soon as the left turn signal is activated, the fuse blows and the signal goes fast. The front bulb does not blink, the rear is fast. I also removed the front bulb and the fuse still blew, so it seems like something is wrong before the front bulb. Unfortunately, I am a complete electrical ignoramus with diagnostics. I think I understand basic electrical concepts, but the only thing I can do with my multimeter is to pound in a nail. My battle plan with electrical problems is clean, clean, clean, which often works...except this time.

I removed the left turn signal and cleaned all of the contacts. Most seemed Ok. I cleaned the G106 and G116 grounds. I also replace the flasher unit. No success.

I have read every post I could find on blowing fuses and fast turn signals, but too often they say things like 'find the hot wire' and 'it would be easy to find the wire shorting with an ohmmeter'. These may be true statements to most, but not to me. I have a Haynes Electric Repair manual and a Craftsman multimeter manual, but I feel like I am trying to learn Latin.

Is anyone that is well-versed in electrical diagnosis willing to give me a next step? I know others are as weak as me, so it would be greatly appreciated. I'll do my best to document my work.

Remove the turn signal housing again, and check very closely the wires connecting to the bulb housing--brown wires are ground, all other color combinations are hot. Remove the hot wire to the turn bulb and inspect it very closely for cracks in the insulation, especially around the spade connector. Check also that the connector on the bulb housing is not bent in such a way that the hot wire is close to the housing itself or a ground connection. You apparently have a ground fault in the lead to the turn bulb (sorry, I don't have the color combinations for the wire to your year car) and it is most likely to be somewhere along the wire once it leaves the wire loom.
Report what you find, and we'll go from there.

ossiblue - thanks for the next step. I removed the backing plate and photographed the wires. The insulation on the wire themselves looks pretty good and I tried to clean up everything. One thing worth noting. There was a clear cover over each spade. They seemed to have dried out with age. One tore badly enough that I threw it away, they other has a large tear.

I noticed the ground wire is attached directly to the backing plate. Could the current be arching from the spade to the backing plate and causing the circuit to gound? I don't think there is any direct metal to metal contact. Thanks.

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Bump. I removed the metal housing inside the turn signal, installed a new fuse and tried the turn signal. Blown fuse again. The wires look a little close together in the picture, but they are not. I assume this means that I have an issue with the wiring before it gets to the turn signal.

Can anyone suggest a next step to continue to diagnose? Is there a way to set the turn signal switch on the column? I really am at a loss and hate to replace parts that are still good. Thanks.

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Follow the wire loom back from the turn signal housing until you find a plug connector--I believe it will be round and have six pins and is usually located where the loom passes through sheet metal. Sorry, I don't know where it is exactly but you should be able to find it. Pull the connector apart, put in a new fuse, and try your turn signal again. If the fuse doesn't blow, the fault is somewhere between the plug connector and the turn signal housing, or the connector itself. If it does blow, the fault is between the connector and the fuse block. Let us know what you find out.

L.J.

Thanks, I will look tonight when I get home from work. I did try to follow the loom yesterday, but couldn't see where it went because of the wash fluid reservoir. I may need to remove some of that to see what is going on. I will post what I find.

Try disconnecting the engine compartment light.

L.J.

I looked tonight and there is no multi-pin connector for the front light for an '86. The wires come out of the harness through a grommet above the battery and into the front left headlight bucket. I could move the smaller loom of wires back and forth in the grommet, I am confident that I couldn't do that with a pin connector. I did disconnect the wires in the headlight bucket and tried again, the fuse blew.

The process of elimination now eliminates the wires after the headlight bucket. I am following the story pretty well, but I have no idea what to do next. Hope you or someone has some thoughts.http://forums.pelicanparts.com/uploa...1245115795.jpg
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JKelly - Thanks, I did disconnect the trunk light, but am starting to run a little low on 5 amp bullet fuses, so I will wait until I test take another next step. The trunk light should no longer be a factor.

Greg,

You may as well get some use out of your multimeter, and save your fuses. Set the meter to 12v DC. Remove the fuse from the turn signal circuit. Connect the + lead of the meter to a power source (use one of the fuse terminals that is always powered.) Connect the "- " lead to bare metal on the car and you should get a reading of about 12v. Now, leave the + lead connected to the terminal, and touch the negative lead to the terminal in the fuse block where the wire to the turn light is connected. If you get a voltage reading, then the wire leading to the turn light has a ground fault (as you suspect). Use this method as you trouble shoot the system. If the wire to the turn light is good and the spade connector at the end is not touching a ground, you should get no reading on your meter. This will save you fuses.

I believe your turn light wire is gray with red stripe. If you are getting a voltage reading from the above test, start moving the wires close to the fuse block and see if the reading changes (goes to zero.) Proceed along the wireloom toward the turn light, flexing it as you go to see if you can find where the voltage reading stops. You possibly may see a place where some damage could be causing your problem.

As far as the plug connector goes, I was using a wiring diagram from an earlier car, so you may not have one. However, follow the loom all the way back to the fuse block just to be sure.

most of these issues where the one flasher light trips a fuse is usually in the bulb housing where it fell apart, but you disconnected the wires to the housing and the fuse still blew?

so far I figure the ground is between the fuse and the turn light assembly?

I guess I would test that the upper part of the fuse connector is flashing by using a test light at the connector.

if the test light flashes it would confirm the ground problem between the fuse and light housing. Then I might run some test wires between the lower part of the fuse connector connected directly to the housing to see if the fuse still blew?

If I still couldn't find the ground I would use a ground fault tester aka short finder. One part connectes where the blown fuse is and the other part is traced around the wiring to pin point the ground. It should cost about $25 at the auto parts store?







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Greg,

As you've discovered, the wiring to the turn light is secured in a loom that has very little chance for vibration or abrasion, that's why it's a puzzle where the fault is. Look very closely all along the loom, where possible, searching for any signs of cuts, abrasions, or heat/melting. I suspect if you ran a long jump wire from the fuse to the turn light as RoninLB suggests, it would work correctly without blowing a fuse. It is so unlikely that a car of your vintage would have a ground fault in a secured loom that I still suspect some mechanical damage or touching of uninsulated wires. Keep up the hunt, and keep us up to date.

I have the Carrera Bentley book w/wiring but I think it's unnecessary?

You guys are too kind and I am really appreciative. Unfortunately, I am in Portland, OR tonight and tomorrow night. I am home Thursday and will follow all the instructions. I think some of this might actually be sinking in, I have just never had any teachers.

RoninLB - If I install a new fuse, the left front never blinks, but the fuse blows. The left rear blinks at the same speed as the dash indicator. This occurs even in it's current state with the bulb removed at the blinker, the blinker disassembled and the wires disconnected in the left headlight bucket. I have the Bentley book for '86 and can scan any schematics if needed.

L.J. - I will examine the loom more closely. It is really tight in there, but I will figure it out. I will run a test wire to confirm. Would I need to disconnect the existing wires as part of the test? I am assuming that I would disconnect them from the top of the fuse, not the bottom.

Also, I want to invest in a short finder. I have looked for reviews on them, but haven't found much. Is one brand better than another? I have seen things like the ECT2000 to an old used Mac tools unit with a needle gauge. Thanks again to both of you.

One of the best forest trails in the country is about 60 miles SE of Portland. It's in a Nat'l Forest and is called Bagby Hot Springs. Park in the lot, trail is 30 minutes walk to a group of hot tubs. I spent a week in its campground. The area is some of the finest of the Cascades.

The short finder is a simple tool sold by many. Either go snap-on or walk into a parts shop the pros use and see what they're selling.

The top part of the fuse receptacle should be power in? Disconnect wires that are on the lower section and attach a new wire there.

That should work as it's difficult giving advise without being there.

I had a similar problem, as you describe. I'm also fairly unhandy with a multimeter. After going through the local autoparts stores' supplies of 5-amp bullet fuses (man, are those impossible to find), a fellow Pelican promptly popped out the headlamp on the same side, noticed what looked like a bit of chafing on the inside of the bucket, pulled apart the spade connector and plugged it back together, and voila--no further sacrificial fuses. What I thought was a bit of chafe in the paint was actually a loose connection, and the slight burn on the paint due to the arcing of current to the headlight bucket.

I did a little diagnostic work with my multimeter this evening. The battery was 12.6 and always hot circuit was 12.59. I tested the circuit without the ignition on and got 0, but then it struck me that there was no power in the circuit so I turned the ignition to on and got .2.

Next, I disconnected the wires on the bottom of the fuse, ran a test wire to the light and it worked properly, fuse was fine. So, it appears as though there is a problem with the wire between the fuse and light. My body has run out of gas this evening, but tomorrow morning I will hook up the turn signal light to the wires in the headlight bucket to see if I can isolate the location of the fault to between the fuse and headlight or headlight and parking/turn signal.

If either of you have any additional suggestions, I am all ears. Thank you again. I can't tell you how much money I am saving by doing this myself. I sent Wayne a note to remind him how important the board was to so many of us. I probably couldn't afford to keep the car without the board, so thank you for making it so worthwhile.

I will post the results of my test tomorrow morning. I am leaving on family vacation on Saturday so would love to figure this out tomorrow if possible.

I hooked up a test light to operate in place of my turn signal at the headlight bucket this morning. Unfortunately, the fuse blew. I am going to assume this means the problem lies between the fuse and the headlight bucket. At least that is my current theory. I am going to test it again, before I rip into everything, just to be sure.

Is is correct to assume that since the fuse is blowing that there are two hot wires touching somewhere and that is causing the fuse to blow? It seems to me if there were a bad ground, the light might be dim, but the fuse would not blow. Other than looking for a cut or abrasion, I have no idea what I am looking for.

I think I will buy a short finder since I know the approximate location of the fault. There sure isn't much room in there, so I am going to remove the windshied washer bottle and approach it from the wheel well. Any thoughts from anyone would be greatly appreciated.

A view of the loom access point under the fender looking in from the turn signal opening.http://forums.pelicanparts.com/uploa...1245441132.jpg

The whole metal body is ground (or one of your "hot wires"). When you disconnect the wire at both ends do you get an ohms reading to chassis?

In your picture that flange hasn't worn through the cable has it?