For the past six months I have been hunting down an electrical problem I have been having. I have an electrical draw somewhere and can't figure it out. The emissions light flashes intermittently, the radio will short out especially when the headlights are on, my gauges are reading high (before I replaced with mechanicals) and the headlights will flicker. This happens whether I hit a bump or not. Could the alternator be going bad? Where is the common link between radio, headlights and the emissions light? I need to get this solved getting really frusterated!!!! Owe by the way...the cruise control has also stopped working!

 

WHAT ARE YOU WORKING ON!!!!!!!!!!!!! First of all, they all are electrically common as is ground.What is your voltage reading when all this is happening? Also, run a ground from engine to frame and to battery neg post.If external voltage regulator is used- make sure it is grounded-ohm meter will come in real handy to check how good a ground you have.Guessing you have pre 92 Bronco because you mention emission light- and why to you think you have an electrical draw? Does battery go dead over night(like something left on-example, glove box light,sunvisor vanity light etc.....)

 

Yeah that would help...86 XLT Bronco fullsize (302 EFI). Prior to turning on the headlights, radio, heater etc. The voltage is 14...after 11-12. The battery never goes dead...of course most of the time I'm only going 3-4 miles per trip. By the way Internal Voltage Regulator.

 

The problem sounds like you are getting a backfeed somewhere. All of the accessories, radio, clock, power windows etc. are fed through the ignition switch. BEFORE the power even gets to the fuses (6, 11, and CB 14) for these circuits, the ignition switch has to be in the RUN or ACC position. I only say this as it may be helpful in hunting down you intermittant power surges. With the ignition switch OFF, fuses 6, 11, and CB 14 should have no voltage reading to ground. If they do for any reason pull fuse 6 and recheck 11 and 14 for voltage to ground. Repeat this for 11 and 14. If the voltage to ground does away with the removal of any of them, you have a power backfeed from the circuit on that fuse/CB. If the voltage does not go away with the removal of one at a time, try removing all three and rechechikng for voltage at the upper end of fuse positions 6 and 11 and the lower end of CB position 14. If there is voltage to ground from any or all of these positions then the ignition switch is suspect. If there is NO voltage reading to ground at any time through this process, then the problem doens't exist between the ignition switch and the circuits that feed the components in question.

The only location where the headlights and the radio may have a problem backfeeding is in the illumination circuit for the radio. If for some reason the illumination circuit OR radio power circuit has a bad wire somewhere, its possible that the power is backfeeding.

The emissions light would suggest situation is creating enough of a change in voltage to the system that triggers the light. Call it a a short, call it a backfeed, its probably not going to be an easy find unless you can readily see some sort of breakdown in the wiring or a switch somewhere. I know I haven't necesarily answered the question here but if you can use this to help troubleshoot you may be able to narrow down the location of the problem.

 

I'll do some checking. I could not find any suspect wires or fusable links under the hood. I suspect it is in the cabin somewhere. Thanks grey!

 

Bad grounds will cause as Grey stated a back feed situation seen this often back in mid 70s.Ground cables left battery and had a bracket soldiered onto it midway- attached with bolt securing it and voltage regulator than continue on to engine block-thus ensuring chassis and engine are grounded.You coulded buy the replacement ground cable with the bracket on it- without it , yes backfeed problems- all backfeed problems are ground related!!!About the only 11-12 volts when everything is on-- is this at idle(very low idle I would think)and does it go up as rpm increases.There is a test pin(bolt head) on back of voltage regulator you ground to see what max voltage the alt will put out. You can replace the regulator as well as the 2 brushes.Biggest problems(electrical) we encounter and have to call Ford Hot Line are always asked-Have you checked all grounds first.

 

if you suspect the problem is intermittent and somehow related to move ment as in a bad wire or connection get yourself an ameter and put it in series with the battery.while an assistant monitors the reading you can go to any components or wiring you suspect and move/shake/unplug/evenheat if you suspect a component that becomes corrupt with rise in temp.keep in mind that when an accessory is turned on the reading on the ammeter should corispond to a certain value.if you turn on the radio and see a draw of 20 amps you know there's a problem.jc whitney sells an inductive type dc ammeter thats said to pinpoint shorts through insulation and metal.knowing a little about ac theory i don't think it will read through metal but reading through insulaation is definitely do-able
good luck shovelhead

 

Trublu...the 11-12 volts is when the truck is at warmed up idle...apprx. 1000 rpm. Does not appear to increase with RPM output. I know for a fact the negative ground cable gos from the battery to the engine block...no intermediary bracket. Sine I am not very good with the electronic aspects what would be the best way to test the alternator...I do have a brand new multimeter. What is the best way to test the battery? Thanks for your help it is really appreciated!

If it is the alt. I will make the move to a 3G alt.

 

3g would be a wise move. I don't like 1 wire alt. because they need certain rpms to excite(start to charge-that is above what the bat volt is,runing or not) and sometimes below that rpm they quit charging(engine load, ac on ,heatlights on, radio on, and in drive sitting at stoplight and not charging untill bat. goes dead) At 1000 rpm the alt should be excided(will be excited when engine is running) and charging at least 13.5 or more.On the back of the voltage regulator the one exposed torx head bolt should say test on it- ground it with a jumper wire with truck running- read voltage with multimeter , should go to approx 15 volts or higher-If it does, alt is good, volt. reg bad. as top bat.- a good tester will show cold cranking amps- hard for me to suggest a good tester, used to use Bear tester but now we use our Ford brand(and supplied by them) tester in my dealership.Do me a favor and take a vise grip and grip frame somewhere and take a jumper cable and hook to bat. neg. post and vise grip(after getting charge system up to par) and let me know if other wierd things still happen or not.

 

[quote]On the back of the voltage regulator the one exposed torx head bolt should say test on it- ground it with a jumper wire with truck running- read voltage with multimeter , should go to approx 15 volts or higher-If it does, alt is good, volt. reg bad.[quote]

I'll try that! This thing is REALLY starting to **** me off! I go to work when it is dark out (hense use of headlights) and come home when it is dark out...and all the while the radio is shorting out ever 30 seconds! I need my music...ok done venting!

As far as the vise grip idea, the shorting out of the radio, headlight thing emission light thing dos'nt fail until I am heading down the road. Everything is ok sitting still...when there is no load on the alt maybe?? Still may be a short somewhere??

TRU...thank you very much for your insight I will do the tests you suggest and let you know. May not be for a couple days...Keith Urban concert tonight! Maybe on Friday or Sat. Thanks!