[Shop-talk] electrical problem with truck

Thu Aug 12 15:39:17 MDT 2021

Glad you found it!

Peace,
Pat

Pat Horne 
We support Habitat for Humanity

On Aug 12, 2021, at 4:34 PM, john niolon <jniolon at att.net> wrote:

well, that's three days or so I'll never see again... started over on the diagnosis... A fellow ford guy in Canada mentioned something about the alternator exciter wire being used when alternator was larger than 80 amps. I didn't use one... I called EZ-wire tech guy and we discussed it. He assured me that with a one wire unit the exciter wire wasn't used (it gets itself excited ) As we talked he asked what my battery voltage was when the alternator was above 1500 rpm and I told him in the 13 volt range. Then he asked what my alternator voltage was and it was 14.6 or so... He said just to check it and bypass all the wiring to run a wire straight from the alternator to the battery +... I asked him if it cured the problem should I just leave it in place... he said sure , that way you are getting charging voltage straight from alternator

So I built a #4 cable and installed it from alternator to battery +... guess what ??? 14.6 at alternator and 14.6 at the battery... All this high tech diagnosis... was just an exercise... At least I know that all my connections and terminals and electrical stuff is good and well grounded and blessed ., I think I'm gonna call him back tomorrow and get him to explain EX-wires reason for not having that direct charge wire in the first place. Thanks  for sticking with me trying to figure this out and for all the information, ideas, suggestion, CWAGs and un mentioned comments about how I can be so dumb and yet so good looking at the same time...

john

John, here’s a little electrical theory for you, hope it helps. 

Resistance measurements on a vehicle are not generally useful for circuits that handle higher currents but works better for circuits that deal with signals. It is useful just as a open/short diagnosis. Here’s an example. A wire carrying 40A current with 1V drop will have a resistance of .025 ohm, much too low to be a real indication. Voltage, either to ground (the same ground point for all measurements) or voltage drop across a wire is the best way to find bad connections or undersized wires, your readings will not be near the end of the range or the meter. That’s why I recommended the series of voltage readings all along the wire from the alternator to the battery. 

This approach also works well for grounds. When working with grounds it is best to use a single ground reference point or do voltage drops across each ground wire. 

Peace,
Pat

Pat Horne 
We support Habitat for Humanity

On Aug 9, 2021, at 3:10 PM, john niolon <jniolon at att.net> wrote:

 Pat, while the battery was out I checked resistance on all battery, starter and ground cables... all read from .003 to .004 ohm resistance end to end
 also rechecked the charging voltage again with engine at 1200 rpm  14.6 volts... as I increased the rpm the voltage flickered down to 14.3 - 14.4 to  then
back up to 14.6 as rpm decreased back to 1200

did this both with VOM leads on battery terminals AND alternator terminals

j

----- Original Message -----
From: Pat Horne <patintexas at icloud.com>
To: john niolon <jniolon at att.net>
Cc: shop-talk <shop-talk at autox.team.net>
Sent: 8/9/2021 1:30:34 PM
Subject: Re: [Shop-talk] electrical problem with truck
John,
Check charging voltage @ alternator post, alternator terminal, terminal on other end of 1/0 cable, post that terminal connects to. If you can get to the conductor in the 1/0 cable, get that too. That should be enough to find the problem. 

Peace,
Pat

Pat Horne 
We support Habitat for Humanity

On Aug 9, 2021, at 1:02 PM, john niolon <jniolon at att.net> wrote:

sorry for slow response... helping daughter and sil move...priorities!!!

Monday a.m. report

fresh charge on battery 40 amp for 30 minutes on saturday trickle charger since then .. battery voltage 13.4 this a.m. checked with two different meters

hooked up H.F. 500 amp load tester, voltage reading same as VOM at 13.4
voltage at frame rail terminal also 13.4

battery has 800 CCA capacity
started test... over 15 second test the battery slowly dropped to 320 amps and voltage read 10.8 (still in the green scale)
stopped test at 15 seconds and two minutes later battery was back up to 12.7

next step will be check alternator output at battery and terminal point

ok... started truck... engine at 1200 rpm
meter on alternator o/p- voltage is 14.6
meter on battery voltage is 13.5

hmmm...1.1 volt drop in 4' of 1/0 cable....that don't sound right
need to measure resistance of cable I guess...

as an aside... checked voltaged between frame ground and the case of the alternator... 0.0001 volts

I also took battery back to Wal mart and Quintella checked it...  battery is good based on her years of
battery experience

----- Original Message -----
From: john niolon <jniolon at att.net>
To: shop-talk <shop-talk at autox.team.net>
Sent: 8/6/2021 8:58:12 AM
Subject: [Shop-talk] electrical problem with truck
jeff….     regular led acid battery ??     Everstart Maxx27 800 CCA  regular Walmart battery

When it died, did any of the electrical items still work?  Lights, etc.?  when it first occurred ,, when I tried to restart, .. starter just clicked and I remember the a/c fan still blowing

Donald...  How large is the cable from the alternator to the battery?   feed from battery to alternator is #4 wire

Dave... I was thinking a dirty battery clamp.    battery clamps are new this year and clean, no corrosion on connections

John...   How is the volt meter in your truck grounded, to the frame or to the motor?    voltmeter in dash is grounded to dash frame  voltmeter used to check under hood is grounded to frame not engine.  I'll go back and check ground connections. Alternator has a ground terminal of it's own... it's #10 wire grounded to the frame and of course the alternator is grounded through it's mount.

Pat...  what is the relationship between the frame terminal & the rest of the electrical system?  Terminal on the frame rail is fed by a 4' piece of  #4 wire from the i/p solenoid lug where the cable from the battery is connected to the solenoid.

Jimmie..    What's the voltage at the terminal with those accessories 'on' but the engine 'off'    hmmm ?? don't remember checking that, …  I'll do that
 How big is the alternator?    100 amp single wire from CVF racing

ya'll have given me lots to check and recheck and some I haven't thought of...   going back through my diagnostics and check connections too.  I bought a 500 amp load tester yesterday and will put sufficient load on the battery.  Battery is under the cab and I have to lower it to check it out and with the low truck, I have to raise truck on jackstands.. silly me, I thought battery would be a low maintenance item ...duh.   so checking at a shop somewhere is a very large pain.

points I'm considering.... larger ground wires from frame to engine.... alternator to frame and check resistance from solenoid lug to the terminal on the frame...   the saga continues

thanks for all the replies and points to check..   you guys are the best

john

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