Keith Browning Posted May 6, 2009 Share Posted May 6, 2009 I am taking a phrase and a lesson from Bruce's books in saying CLEAN POWER is something to remember. The idea is that dirty and loose power and ground connections can cause problems that you never would have imagined possible. Sure, we all know this, but it is always worth reinforcing. Yes, I just had a head scratcher... wait while I pull the rest of the concrete from my hair... Had me a 2000 F350 in with a flashing TCIL and P0720 in memory. Passes KOEO and KOER. Performed the appropriate pinpoint tests and no concerns found - workshop manual directs to replace the PCM which I didn't as I wasn't satisfied with that. Data logger and a road test revealed an erratic VSS signal but the DTC was for the OSS sensor. This happens if you get a VSS/OSS discrepancy. Again I look over the wiring and again I find nothing so I slapped a VSS in it and let it go after a good road test. Comes back a week later, same concern, same code, same test results. "Let's try an OSS sensor for shits and giggles." Ummm, nope. Then the truck starts doing strange things like the dome light going on and off, the engine bucks and dies (PCM reset) and the turn/hazard lights stop working. I snooped around in other modules, no DTC's but GEM B+ and VSS are so out of range it was insane! B+ 16-17 volts and VSS 80 MPH idling on the lift? Long story short, the main battery terminal, which had been replaced at some point was one of those two piece deals with a clamp and bolt on section. Well, it was tight on the battery post but both parts were not bolted tightly together. I took it apart and cleaned off all of the carbon from the arcing, serviced the terminals and verified the repair. Sometimes we need to look closer and not overlook basic things. I am not totally embarrassed so I thought I would share my story as a reminder. An occasional kick in the ass helps keep us thinking! Quote Link to comment Share on other sites More sharing options...
DwayneGorniak Posted May 6, 2009 Share Posted May 6, 2009 One of our apprentices here just had a Superduty with a 7.3 L that would constantly kick out the AUX Idle Control anywhere form a minute to a couple of minutes after running. VSS was spiking and the PCM would shut down the idle control. Right from the beginning of the job, he had to constantly boost the truck because the batteries were absolutely screwed. He had been in contact with Hotline numerous times and told them about the batteries and suggested changing them. Hotline recommended against it and couldn't see how the batteries would cause the issue. Finally after a new Aux Idle control box and a new alternator and I can;t remember what else, the young lad said to hell with it and threw two new batteries in the truck. And low and behold: MAGIC-it's fixed. Simple electricity is something I "TRY" to never overlook. But we are all human and our job's can sometimes play tricks on our minds. I like the term "CLEAN POWER". I will remember that. Quote Link to comment Share on other sites More sharing options...
eastendpowerstroke Posted May 7, 2009 Share Posted May 7, 2009 A few years ago I had two E-450 box vans 7.3L's from the same moving company towed in two days apart both for a crank no start. I chased the problem around on the first truck for hours, no codes seemed to have everything it needed to start but wouldn't. I had the Ah Ha moment when I tried to monitor some pids with NGS because another tech was using the WDS at the time, when cranking the NGS would shut off. Long story short the vans had the setup with one Battery under the hood and one on the frame rail with the big brass nut connecting the battery cables together under the hood. when cranking the B+ would drop to about 8v just enough to shut the pcm off and not start because the big brass nut was a little loose so it was only cranking on the under hood batt. I don't know how long I would have chased that problem if I hadn't had to use the NGS. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted May 8, 2009 Share Posted May 8, 2009 Yep, that's the reason I put that material in my presentations. I've been burned by dirty power more times than I can count..... Off to ASE tonight. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted May 8, 2009 Share Posted May 8, 2009 Had a good one on a '08 E-450 ambulance. No start, ended up being the ground on the right front fender area. The glue had ran out of the heat shrink and got under the ground eye between the eye and the fender. Got lucky cause I found it pretty fast. It could have gone the other way and took forever to find, you know "in the last place you look" Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted May 8, 2009 Share Posted May 8, 2009 The rest of the story... The decision wasn't to "throw batteries at it" and I'll explain why.... Fairly early in the going, it was discovered that AC ripple in the charging system was high... too high. The decision was made to change the alternator.... Sidebar.... in years gone by, we would look at "alternator ripple" on a scope... We were looking for what you might call "gross defects". Shorted dodes, open diodes... If you had bad enough ripple, the worst that would happen would be noise in your speakers... Back then, most of us listened to 8 tracks or AM radio anyway.... Today.... there is an accepted spec on alternator ripple... 450~500 mVAC (milliVolts AC) but some delicate electronics can demand as small as 200mVAC. In this case the alternator was changed and the symptoms persisted... It took a while before AC ripple was retested and sufficient credence was given to that fact. In effect - the concern came up and kicked us all in the nuts and then laughed at us... Along the way, (and the VSS wasn't spiking - it was merrily cruising along at various speeds) it was noted that the ABS module was reporting a moving vehicle (the VSS is hardwired to the ABS module) yet it wasn't passing this info over the network... nothing to the speedo via the cluster and nothing to the PCM. Yes... we tried a known good ABS module with no change.... bells should have been ringing... So... ripple gets revisited... and there is still too much ripple.... (let's get a tattoo on our foreheads called "smack head here"). Flip the FEAD belt off the pulleys and retest.... Wait... did I just say "flip the FEAD belt off the pulleys?". And the concern is GONE? Lessons learned to this point.... We set out to get rid of high ripple.... Along the way, we lost sight of our goal and all we did was change an alternator... In years gone by, we checked for alternator ripple... gross amounts of it.... Today, we are looking for charging system ripple... tiny bits of it. Automotive batteries have internal resistance - a properly functioning, fully charged, lead/acid battery was, to my training, about 1 ohm. Working properly, the battery acts as a buffer for ripple.... but if we change that resistance... increase it as in what might be a failing battery (or even dirty terminals or similar concerns), this can exacerbate the ripple. At one point, we were so obsessed with having the appearance of doing <something> that we began to neglect thinking about what we were doing. Until we flipped the belt off the pulleys. - until we saw the ripple disappear and the concern evaporate along with it... How many times have you quoted for batteries AND alternator because something didn't "feel right"? There is a lesson to be learned from this incident... it's called "pay attention". If you make a repair decision - have a reason.... with this in mind, we should be able to measure a difference in SOMETHING from the pre-repair state to the post repair state... In this case... if you set out to reduce charging system ripple - don't stop simply because the alternator is new.... This repair should have been a lot fucking easier than it was.... Of worthy mention.... TSB 06-19-12 addresses an alternator frequency concern using the lab scope in VMM. This test is NOT the one I was referring to for alternator ripple.... This test is looking for RFI over VRS sensor circuits. Do not confuse RFI with AC ripple (though they can mimic each other). FWIW, newer vehicles have a GEN_HZ PID - google "synchronous speed". For a better understanding of batteries (and I will let you know if I ever finish reading this dry shit) CLICKY . The best part about this trade? No matter how much we know.... No matter how much we think we know... there is always something new we will learn tomorrow.... Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted May 8, 2009 Share Posted May 8, 2009 The best part about this trade? No matter how much we know.... No matter how much we think we know... there is always something new we will learn tomorrow....That is so true. What is worse is knowing something and then forgetting it because you didn't use it and having to learn it all over again the next time you are faced with the same problem. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted May 8, 2009 Share Posted May 8, 2009 Today.... there is an accepted spec on alternator ripple... 450~500 mVAC (milliVolts AC) but some delicate electronics can demand as small as 200mVAC. I suggest you revise your spec for AC ripple. 500mv is an antiquated number that was set when dirt was still white (remember? ) and not appropriate for modern vehicles. Most vehicles measured today are about .02VAC (20mv) measured at the battery and .05VAC (50mv) measured at the alternator. In doing our electrical classes we've tested literally hundreds of vehicles. I suspect diode technology has improved over the years and the need for cleaner power has obviously increased with the level of electronics we see these days. I recently sent an new IH back to the dealer for a replacement alternator that measured 400mv, and they did replace the unit. It measured 20mv after replacement. Have a great weekend! Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted May 9, 2009 Share Posted May 9, 2009 Thanks for the heads up, Bruce... The spec we used was, indeed 50 mV but my old memories got in the way... In my defence, I did search the net and the only reference I could find was the 200 mV suggestion... For a spec this important, one shouldn't have to search so hard... Considering that alternators were still one of the latest amazing steps forward in automotive technology, I can vouch for the advances made in all facets of semi-conductor technology. Even as late as 1970 you would sometimes hear someone ask how you polarized one of them... was it like a generator? Truthfully, now... what do you think of the colour we finally chose for dirt? Quote Link to comment Share on other sites More sharing options...
Jeff Adema Posted May 20, 2009 Share Posted May 20, 2009 Dirt is still white, Jim. Just look out your window! Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted May 20, 2009 Share Posted May 20, 2009 Yep... I think we have close to 8 inches of "new dirt" so far today (that's about 20cm for the inchamacallitly challenged)... and more dirt is still falling... Quote Link to comment Share on other sites More sharing options...
Aaron Posted May 23, 2009 Share Posted May 23, 2009 I had to fix the air conditioning in my truck today. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted May 24, 2009 Share Posted May 24, 2009 I came across an excellent example of clean power the other day. So I thought I would share it here. A guy that I work beside (who shall remain nameless to protect the innocent), had an issue with clearance lights on a dump body. He gets his handy dandy test light out and gets to work on finding the problem. Well a few short minutes later (actually 30 of them) I here swearing and small fits of rage ensue. Seems this fellow gets agitated easily, which would lead me to think he is in the wrong field. Anyway another co-worker walks bye and starts to observe the “show”. Then he asks if he could be of assistance. The tech being somewhat proud of his own capabilities declines the help but can’t resist taking the opportunity to vent. He procedes to say that he has no power to any of the clearance lights, including the ones that are lit up at that very moment. The other fellow suggests that his test light might not be grounded properly. Tech “A” steps back in a huff, and exclaims I’ve got the alligator clip grounded directly to the negative battery post, see! Tech “B” follows the cord of the test light out of the guys hand and directly to a 12 volt car battery lying on the floor at tech “A’s” feet. Which makes me comment that just because you brought your car to a dealer, does not mean you are going to get dealer quality work. Quote Link to comment Share on other sites More sharing options...
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