Ahhh, 'lectickcity, you say?

Jim Warman · March 26, 2008

I have an 07 F350 sitting on one of my back burners... A host of electrical problems are plaguing this thing... no 4X4, no turn signals, can't remember what else....

For some reason, they keep giving electrical to apprentices when we are busy..... too busy to spend several days having someone furble around with errant electrons.

Again, when I say "good ground" - I mean battery negative post.. and when I say B+, I mean battery positive post..... "convenient sources" aren't reliable.

Step one, naturally, is going to be to test all the fuses. All of them because the manuals never have misprints, right?

Step two is going to be looking at the wiring diagrams. And this has two reasons. First, if we didn't find any blown fuses in step one, we are now going to see if any fuses are missing.... Giggle if you want, you will not believe how many guys get hung because a customer stole a fuse from another location to get is phone/Ipod/whatever working and "forgot" to mention it.... and the number of hours spent by a tech testing circuits that simply aren't powering up.

The second reason for going to the manual, is to see what the circuit does. For "my" truck, the apprentice found F2.27 open. For some reason, he'd decided to go to the vacuum pump before checking fuses.... He disconnected the plug and probed the power side with a test light to find no power....

And here's where attention to details is going to help.... After he found no power at the vacuum pump plug, he decided to check the fuses. Finding the blown fuse, he replaced it, turned the key back on and remembered that he'd left the pump connector unplugged. The pump ran for a couple of seconds and stopped. Not a big deal, but it kept him from seeing where all the smoke that filled the cab was coming from. It took a while for the fuse to blow... long enough to smell really bad (and yes, the fuse was correctly sized).

So... how are we going to attack this? We know that F2.27 blows pretty quick.... So we're going to go to section 13 in the wiring diagrams and see what this puppy protects. To make life easier, we know that the vacuum pump is one of the affected components. Let's go to the vac pump in the manual and look at the fuse. Just below the fuse, there is a little arrow pointing to a link to page 13-15. If we click on that, it takes us to the power distribution section. And this shows us everything that fuse protects....

Just to add some drama... and because it is very late, my floor still isn't finished and tomorrow is going to be a f#ckshow.... we'll leave you in suspense. And this will give you all an opportunity to consider the next step.....

slim · March 27, 2008

Hey Jim, you should write an article about how true professionals diagnose electrical problems. Then you could get paid for standing on your soapbox./forums/images/%%GRAEMLIN_URL%%/grin.gif You do have a way with words while explaining elec diag.

LARRY BRUDZYNSKI · March 27, 2008

Jim I feel for you, but you have been working on that floor seems like weeks now.

Quote:

Just to add some drama... and because it is very late, my floor still isn't finished and tomorrow is going to be a f#ckshow

By the way how did the f#ckshow go today? /forums/images/%%GRAEMLIN_URL%%/grin.gif

Jim Warman · March 27, 2008

Larry... according to the Town of Slave Lake, I've been working on stuff for five years now (when my permit was issued). As of tonight, the diningroom floor is done.... One wall to finish and it will time for trim.

The f@chshow went like a f@ckshow.... I have a Service Manager putting on coveralls.... How the f@ck are you going to steer the boat of you are busy paddling????? This bothers me... The more SMs we go through, the closer they will be to asking me to fill the position... Read my lips.... "I am NOT a service manager". I am a "dink"... I have reached my goal in life and I refuse to change....

But now you gone and done it.... We'll come back to this repair tomorrow.... tonight, I file my kids income tax return on the net...

I figured that I'd given guys enough info for a scenario....

Jim Warman · March 28, 2008

When we laast left our "hero"... He was staring at the power distribution cells counting how many devices fuse F2.27 protects... How in Yahwehs name are we to decide where to go? Stick a 30 amp fuse or maybe a straight jumper in and see what melts? Hmmm, not a good idea when we look at the routing of some harnesses...

But if we look close at what the diagrams are trying to tell us.... F2.27 feeds three separate connectors on the back of the CJB. Drop the CJB and disconnect those three connectors... IIRC C270A, C270H and C270J... Just for shits and giggles, we ohm test the circuits to ground.... We aren't looking for anything specific... we are looking for something "odd". In this case, the odd one was the branch from C270A. I came back as less than 1.5 ohms while the other two came in at ~ 12ish ohms. If you feel you need more proof, install a new fuse and insert the connectors one at a time... The cab of this truck had already been filled with some pretty rancid smoke once.... I didn't press the matter.

C270A feeds stuff in the instrument panel... flasher relay, shift interlock and PAM module.... The wire itself, doesn't look like it's been hot - so we can infer that it is likely a fried component. We can resist the urge to go looking for a chaffe on all that sharp stuff under the dash for now...

So... let's look at our diagram again and see what else it can tell us.... And we find C300 behind the right hand kick panel feeding the PAM module. Unplug that and resistance on this branch climbs to about 14ish ohms.... AHA!!!!

Removing the PAM reveals that it has suffered at the hands of a leaking windshield.

Now... I realize that using an ohmmeter for this repair seems to fly in the face of what I've been saying about voltmeters. But, for something like a short to ground, the voltmeter isn't really the appropriate tool.... and picking the appropriate tool is an important decision.

But this particular story isn't about the voltmeter... it's about using the wiring diagrams effectively. Total time on this repair.... including replacing that friggin' module (but excluding the windshield reseal).... less than 2.0. If I was on flat rate, that would put me back on something with gain time that much quicker....

Tony302600 · March 28, 2008

I remember one of these situations. I had a 05 F350 blowing a fuse(cant remember what fuse) but it feed a crap load of stuff. I spent 2 hour's putting 5 fuse'd jumper's after the splice going to each CKT that branches off. ( i used 5amp fuse to see what would blow first. After 30min of test driving i found the ckt that cause the main one to blow. Guy paid for all of it which was cool.

LARRY BRUDZYNSKI · April 2, 2008

Quote:

Read my lips.... "I am NOT a service manager". I am a "dink"... I have reached my goal in life and I refuse to change....

Ahhh, I think I understand the Canubial your speaking...

Back In the day I was offered a Parts Mongers job, stupid me /forums/images/%%GRAEMLIN_URL%%/banghead.gif. I accepted it and made decent money, but wasn't happy, I pretty much lived there(Sorry Jim we know that you still do), had no my time. The worst thing about it was my mandatory labotomy and become a yes boy to the G/M and the D/P. I have to be able to think for myself, had a great crew but had no lust for the job, did it well, but wasn't happy. Did it for about a year, gave it up and had the labotomy reversed, have been offered the same position numerous times but have laughed and refused graciously. I would rather be a "DINK" as you call it, I get more done and am more valuable to the company doing my job.