'77 Bronco Electrical Problems, centec wiring harness isntalled.

[Acwood04]

I'm having an electrical problem with my dash board. I have a 77 Bronco with a Centech wiring harness. When I turn on my turn signals I get a small pulsing drop in power across my gauges and radio power line. I also see the same thing when I put on the brakes. I see a minor drop in voltage at the radio power line from ~13.5 volts to ~12.3 volts when the turn signals or brakes are on. I have a new 100 amp (single wire) Alternator installed that puts out 14.5 volts at the battery no matter whats running. I've checked grounds and they seem to be OK. Is it a problem to have multiple ground lines all connected to the same ground? Anybody got any thoughts?

 

[ransil]

I'm having an electrical problem with my dash board. I have a 77 Bronco with a Centech wiring harness. When I turn on my turn signals I get a small pulsing drop in power across my gauges and radio power line. I also see the same thing when I put on the brakes. I see a minor drop in voltage at the radio power line from ~13.5 volts to ~12.3 volts when the turn signals or brakes are on. I have a new 100 amp (single wire) Alternator installed that puts out 14.5 volts at the battery no matter whats running. I've checked grounds and they seem to be OK. Is it a problem to have multiple ground lines all connected to the same ground? Anybody got any thoughts?

does that "same ground" make its way back to the battery negitive terminal with a heavy wire?

 

[Acwood04]

That same ground does not have a dedicated wire back to the negative battery terminal, however I tested the grounds with a test light and the power source off the fuse box and they seem to be working fine. I replaced the head unit and put everything back together only to find out the same problem that blew the older powermaster alternator perisists. When the truck is running the radio works perfect, but flip on the headlights and the radio cuts off for a second. Sometimes also happens when you hit the brakes. The turn signals also dim the headlights a TINY bit when the headlights are on and you turn them on. The indicator lights for the turn signals on the speedo also seem weaker with the lights on. Also, the gauges fluctuate a little when you turn the headlights on or they kinda tick with the blinker (aftermarket oil pressure,fuel,h2o temp, and amp.) I tested the voltage to the battery and no significant drop like before I replaced the alternator. This is the 2nd high end alternator and I don't want to fry it or the voltage regulator inside. Trying to trace the problem back to the source but It seems there is ample power at the fuse box.. Any thoughts or suggestions would be helpful.. Thanks

 

[Viperwolf1]

That same ground does not have a dedicated wire back to the negative battery terminal, however I tested the grounds with a test light and the power source off the fuse box and they seem to be working fine.

And the test light draws what, 10mA of current? It's easy to push 10 mA through a bad ground. Not so easy to push 40 amps through a bad ground. Take Randy's advice and run a heavy ground cable. Or you can measure the voltage difference between your common ground and the neg batt terminal with everything on. If it's more than .5V your ground is bad.

 

[Acwood04]

And the test light draws what, 10mA of current? It's easy to push 10 mA through a bad ground. Not so easy to push 40 amps through a bad ground. Take Randy's advice and run a heavy ground cable. Or you can measure the voltage difference between your common ground and the neg batt terminal with everything on. If it's more than .5V your ground is bad.

Awesome I will try that right away y'all are great. I had this truck and have been working on it for almost 13 years, put ab 20k in to it, and and makin the home stretch for this to be a daily driver that TURNS heads in Atlanta. Thank you so much for the advice I wish I had found this forum earlier! Here are some pics of the truck, it's originally but I reprinted it with a red off a c-series Mercedes AMG. 105,000 here is what she looks like.

 

[Acwood04]

Well I just got some 8 gauge wire and ran it from the dash grounds to the negative battery terminal, and it seemed to work. In double checking everything I also found that I had a 15 amp fuse for the headlights when it called for a 20. I also installed that. I also ordered a headlight illuminator switch from wild horses that supplements the power to the headlights directly from the battery. I read that it. An help if you get a little headlight flicker when you have the turn signals on so I went ahead and ordered it, probably going to need a bigger battery now as the one I have in it is small in size compared to the size of the tray. I also checked the battery with the voltmeter and the engine running and it stayed around the 12.5-12.6 area while a helper would turn on and off the headlights and blinkers with the truck running. Is this average? I know in my 97 BMW M3 there is a trick with the inboard computer you can do to have it show you the voltage, and I am running like 13.7 or so. What's the normal range I should be seeing on the bronco at the battery with the engine running? I've got a Tuff Stuff 100 amp 1 wire alternator made for the bronco, the pulley and brackets are all correct. Anyways, thank you very much for the help y'all have saved me lots of time and frustration, just wish I had found this forum sooner!!!!!