MasonT

Hi All - I am having a strange electrical issue and have not been able to track it down.

I first noticed it when driving- the car would die when coming to the stop and applying the brakes - with the turn signal on.
At the same time the voltage meter would drop down to zero and sort of fluctuate.
The tranny and other grround connections (the ones that I know of) are all tight.
The car has a good battery with the correct voltage and the alternator is charging fine - the voltage is between 13 & 14 and I checked and tightened the fan belt.
All connections are clean and the car starts right up.
Next I noticed with the ignition on and car not running: Turn signals activate the correct tail-light bulbs but at the same time the interior light and the little heater indicator light start flashing in sync with the turn signal. Then I noticed if I turn the headlights on - the stop/brake bulb starts to blink instead of the outer bulbs. I also notice that the rear trunk light also blinks in sync with the turn signal. I checked the taillight wiring which is correct.
With ignition on - when I activate the turn signal lever the fuel pump starts whining along with the interior and trunk lights blinking.
With the car started it will run fine with headlights on and turn signal activated but the minute I hit the brakes it dies.
I took apart the center console and checked the wiring which is correct.
I removed the wires entirely from the front turn signals, and yet when I activate the lever the interior light still blinks and the fuel pump comes on.
I am going to check the headlight wires also - but at this point I took a break.
Now I am wondering if it is a problem with the turn signal switch itself (on the steering column).
I checked the wiring diagram but I can not seem to trace down the relationships between all the switches and connectors to figure anything out from it.

Any help is greatly appreciated! I had the car apart for rebuild/refurbishing and many of the components were reinstalled and as I went I checked that all the lights, turn signals, switches seemed to be working fine - I only really noticed it when I started taking it for short test rides when it would stall when applying the brakes and turn signal on as described above.

Thank you in advance - Mason

dr914

I would check the ignition switch, the wiring going to the switch, and check that the battery is being charged correctly, 13.2-13.9 volts at 1000 rpm, steadily. if the voltage as measured with a meter at the battery terminals if fluctuating then the voltage regular could be bad, be overcharging and causing your problem. The volt meter is on the brake circuit so it is normal for the volt meter to die when you hit the brakes.

MasonT

Doc - I believe it is the signal/hazard flasher. I noticed on the wiring diagram that the components acting strangely all share the same ground like 10 or 11 (on the wiring diagram.) When I pulled the Hazard switch ON, the fuel pump will go on/off in sync with the hazard clicking noise in the relay, the interior light goes on and off (as described above). I pulled the relay and now sourcing a new one. Without that relay plugged in, of course the signals don't work, however the other components are behaving correctly. All I can think is that there is a short inside the relay sending a signal to the ground terminal and activating the interior light, the fuel pump and messing things up in general. I also noticed that when I pulled the Hazard relay now the BRIGHT light indicator on the instrument panel works - whereas before it didn't. I hope this is the cause - I spent days checking ALL the wiring everywhere and found no issues. I even pulled apart that dreaded center console...
Cheers!

dr914

cannot imagine a turn signal/ hazard / brake flasher unit causing the problem unless it is the incorrect one installed, sounds to me like some wire is inappropriately touching another (so to speak) and causing the problem There are many times problems with this circuit starting with someone painting the car and plugging in the turn signals improperly. of course someone could have relocated the fuel pump to the front and just grabbed a hot wire!

MasonT

Well, I said I checked all the wiring but I did not check the fuel pump - I'll do that tonight and see.

MasonT

Doc - with engine off, ignition off - nothing turned on - when I have all the tail light wires disconnected if I put power to the GROUND wire that goes to either tail light the fuel pump comes on.

The fuel pump is mounted in front as stock (1975) and the posts are different sizes so they can only go on one way - also when the car is running the fuel pump works fine.

What does this mean? Power going to the fuel pump thru the ground wire....( I suck at electrics as you can probably tell.) If I pull the fuel pump relay of course this doesn't happen.

I noticed this because I checked the tail light wiring for the 10,000 time and started checking by putting power to each of the terminals on the tail light with the wires off except the GROUND wire - every time I put power any of the terminals the correct bulb lights up and I hear the relay clicking on the rear relay panel and the fuel pump comes on momentarily just like when the ignition is turned on. The front lights and front turn signals work fine. I did notice some paint on the ground connector spades at the front headlights which I scraped off but this did not help.

With car off ignition off - if I pull on the HAZARD switch the fuel gauge needle goes back and forth in sync with the flasher - I pulled of the top of the fuel tank and checked the connector there and it looks fine and the gauge seems to be accurate when the Hazard flasher is not on - it comes up whenever I turn on the ignition as expected.

I swapped out the turn signal/flasher relay with a known good one just to rule it out - but same symptoms. But 2 things I notice also the turn signal indicate on the tach dial never comes on and I have checked the bulb and it works fine - also the HIGH BEAM indicator never comes on except when I removed the turn signal/hazard relay.

Seems like there is something with the tail light ground wires - how to trace it down methodically? I checked the 2 ground wires under the rear relay board near the blower motor left side of engine compartment and they are bolted down to the body there and the nut is tight. Checked the ground wires at the front headlights 3 spades on each side with 3 brown wires, checked transmission ground strap, battery cables are tight and battery is charged whenever I do these tests.

dr914

So start with the grounds, remove the negative cable to the firewall from the battery neg post and clean, remove the rear transmission ground strap and clean and reinstall, remove the ground bundle on the drivers firewall to the side of the relay board and clean and reinstall, remove the white ground bundle at the right rear center of the engine case and clean, move the ground bundle to the left of the fuse block under the dash and clean

After all of that, please report back,. I do not know about putting power to a ground lead because we have never done that for fear of shorting something!!!!

MasonT

" remove the ground bundle on the drivers firewall to the side of the relay board and clean and reinstall, " BINGO!!!!

Hey Doc - got it! It was the ground connection on the left side of the engine compartment under the relay board. I had checked it before for tightness but this time I took the nut off and rubbed the connectors with my fingers a bit even though I could see bare metal against the firewall - but maybe the connector had some gunk on it or who knows - reconnected and tightened down and now every thing is working perfectly! Lesson learned folks - check them grounds - even if they look good - take 'em off and clean 'em up. I spent many many hours on this and although I am very happy it is solved I am kicking myself for wasting so much time. Thanks doc for your support! Cheers all.

Petza914

Glad you got it resolved.

Deoxit D5 is the absolute best electrical cleaner for this type of stuff. Dissolves any corrosion that exists, improves conductivity, and prevents new corrosion from forming.

cairo94507

Congratulations MasonT. Good work Doc.

dr914

good man for solving it! 914s for the most part have very solid electrical systems, that cause very few problems. MOST of the problems we encounter have been caused years ago by owners and or mechanics butchering the system trying to solve a simple problem.

I am always available for 914 tech advice by phone or e mail r914@autoatlanta.com