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tduncan001's Avatar
 
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Weird electrical problem

So, everything electrical has been working great on the 71 914/4 up until today. you have to love old cars.

After 3 months or driving and not a single blown fuse, I blew the 8 amp fuse that operates the turn signals today. I put another one in and it blew again ( I did this 3 times). I then started to look for causes. When I pressed the brake pedal, my tach and gas gauge would go to zero. When I flipped the turn signal switch, the red alternator light came on within the multi function gauge. I checked again and every time I pressed the brake pedal, the tach and gas gauge would go dead. When I clicked the turn signal, the fuse would blow. All other lights work.

I pulled the emergency flasher switch and it lit up and blinked and then after a while that died.

Now neither my blinkers nor emergency flasher switch works - but everything else does again (all lights, gauges, washer switch, etc. - but no blinkers). I press the brake and no problem with the gauges goign dead or alternator light going on.

Do you think my flasher relay went bad, the emergency flasher switch or something else?
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Old 11-16-2010, 06:16 PM
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I think the problem is in the tail/brake light connections since I had this happen after Garage Los Ponchos did the last paint job and did not hook up the tail/brake light connectors correctly. If nothing was done back there then it could be corrosion or a bad connection.
Old 11-16-2010, 08:44 PM
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The tach dropping to 0 when you step on the brake is a well-known symptom of a blown fuse. I think it's fuse #8 which does this, but I could be mis-remembering. Double-check your fuses; they can be popped but still look OK from the outside. If you remove one and the metal falls apart, it was already popped.

Could also be due to corrosion on the fuse and/or fuse holder. Take a wire brush to the contact surfaces of both to clean them up.

--DD
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Old 11-18-2010, 06:57 AM
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Don't wire brush with the Battery connected.
Old 11-18-2010, 10:03 AM
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I figured that part out. However, after the blinkers and emergency flasher stopped working entirely, and I put a new fuse in, the tach does not drop to zero any more.

That is why I am wondering if the flasher relay or somethign else may have died. I think the post by John Rogers is worth me checking out too.
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Old 11-18-2010, 03:34 PM
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John is correct...it is very easy to get the rear tail light wires mixed up...I have seen this many times after a paint job or the unit was taken out for cleaning or to reseal...it only takes one side to mess things up since the tail and brake light leads are the same....the flasher relay usually doesn't go bad...
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Old 11-18-2010, 05:32 PM
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Maybe something got loose or a wire cover deteriorated because I have not done anything to the brake lights. It just started out of nowhere. Intermittant at first, then the blinkers died 100% but everythign else works fine. Before the blinkers stopped working - when I hit the blinker switch - the fuse would pop. Now with a new fuse in, which also controls the dash lights - my blinkers and emerg flasher does not work at all but everythign else does. And the tach does not go dead when I press the brake pedal.

I am out of town so need to dig into this when I get back.
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Old 11-18-2010, 08:58 PM
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even if you have not done anything to the F/R light units they can be very very corroded from many years of moisture and not ground properly....take the lens off of one and remove the bulbs to check the bases and contacts...good time to replace old bulbs with the proper wattage type...good luck you will find the problem
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Old 11-19-2010, 05:11 AM
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All of my lights and the associated contact points are fine (I double checked them all). There is something else wrong. I took out the relay today and then ran a jumper wire between 49 and 49a (on the relay plug connector) for a test. When I switched the turn signal lever to the right side, both front and rear signal lights came on but did not blink of course. OK - so the right side of the car is fine and yes the relay is bad as the lights do not come on at all with the relay plugged in.

I then switched the turn signal left and blew the fuse (#8). No wires behind the fuse box are burnt or otherwise look like they are touching. I put another 8 amp fuse in and then tried the emergency flasher. Worked briefly and then blew out fuse #11 (Interior light, warning light, buzzer). Don't know why fuse 11 would be a 25 amper either.

So - any further suggestions? I wonder if whatever happened smoked my relay too?
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Old 11-23-2010, 12:30 PM
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maybe the lever switch itself is shorting out????
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Old 11-23-2010, 12:45 PM
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Mine has similar symptoms. I had the signals working fine then I fooled with the door buzzer under the seat. I put a piece of paper between the relay so the door buzzer would stop. Coincidence? I put it back the way it was and no difference. My tail lights could be mis-wired. I didn't install them. Also, with my key in the off position the right tail lamp is on.
Old 12-22-2010, 04:45 AM
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Update!!! I just went out there and fooled around with the e-brake switch. Now:

Ignition switch off- turn signal switch turns on left or right indicators (steady)
Ignition switch on- signals do not illuminate at all

My MGB works better than this, LOL
Old 12-22-2010, 05:04 AM
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The circuit that lights up the turn signals when the key is off is different from the one that makes them blink when the key is on. It even uses different contacts in the turn signal switch, I believe.

The blinking circuit gets its power from the flasher relay. Is yours working? Do the hazard lights work?

--DD
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Old 12-22-2010, 08:32 AM
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Yes. Hazards are fine.... for now. They were blowing fuses the other day.
Old 12-22-2010, 09:34 AM
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I think the next step for me is to actually start testing for resistance on the left side lights as the symptoms point to a short somewhere. The right side works but the flasher relay is fried (I verified that by bridging connectors 49 and 49a on the flasher relay.

Dave, should I test for resistance between the flasher light bulb connection and the flasher relay or is there somewhere else you would approach first?
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Old 12-22-2010, 09:38 AM
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My hazards crapped out the same time as my flashers.
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Old 12-22-2010, 09:39 AM
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Below is a simplified wiring diagram for the turnsignal section.

Measuring resistance to ground is a good way to isolate a short.

Remove the flasher relay and measure resistance from the wire of 49A to ground. Try turnsignals left and right as well as 4-ways on. You should see low resistance of the lamps but not zero resistance. If you see zero resistance, you've found the short.

Old 12-30-2010, 05:56 AM
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This is good, thank you. Question for you as I am in learning: I purchased a continuity tester (basically an inverse test light - has a battery in it). Knowing that my right turn signals work without blowing a fuse and the left turn signal blows the fuse, I was thinking of disconnecting the battery, attaching one end of the tester to ground and then placing the continuity tester on various wires that are not suppose to be grounded. If the test light comes on, I know exactly which wire is grounding out somewhere and can then trace back. I am assuming that the short must be in the left side flasher wires or the switch itself (I hope the latter is not the reason) because if some other wire in the diagram was grounding, both sides of my flashers would blow the fuse.

Does this sound like a good approach?
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Old 12-30-2010, 06:53 AM
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That sounds like a good approach. Try this: do your test with and without the bulbs in place. Remove the bulbs from both the front and rear turn signals and do your test. Your lamp should light for both with lamps in and should not light with lamps out.

I would recommend that you borrow or purchase a Volt-Ohm-Meter. A VOM can be had for as little as $10 and as much as you want to spend. Home Depot, Lowes, Sears, Radio Shack all carry VOMs of varying qualities. $25 should get you a good one.

Being the owner of a 914, this likely will not be the last time you need to break out the VOM.
Old 12-30-2010, 07:08 AM
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I think you are correct as I spent a lot of time figuring out what was wrong with the rear heater blower motor and switch - it works now. I actually have a really nice digital multimeter that I received as a gift a logn time ago and have never used it. Need to find the instructions online as there are 7 different dial functions and a bunch of buttons; looks like way more than I will ever need.

Thanks again for the help.
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Old 12-30-2010, 08:56 AM
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