spitzair

Hello all,
I'd like to pick the brains of electrical geniuses here... The other day I was driving in the company's 2002 Sterling dump truck and suddenly all the engine gauges went to near zero values, and the caution light came on very dimm. Everything else worked as normal, but just the electronic gauges went for a dump. The voltage went right to the bottom, the fuel gauge showed only 1/4 tank even though it was full, the tach was stuck at 600 RPM and the temp. gauge was also reading quite low. The engine ran normally, the jake worked fine and all other electrical equipment was operating normally. Today it happened again 4 times in a row. I found that if you shut the truck down, waited a few seconds and started it again it would go away. The last time it did this, I put my voltmeter to the leads of the alternator, and got reading between 0 and over 200 volts. Yes that's 200 Two Hundred! I don't know if it's my cheap voltmeter or what, but I figure it would be somewhat accurate. The alternator was also VERY hot, I couldn't touch it for more than a second. None of the leads on it were hot at all. ??? And she didn't throw any codes either. Of course when I drove around with the mechanic in the truck it didn't do it. So, I'm very confused. Anyone have any ideas? Could the alternator be taking a trip south anytime soon? Any help would be great since we were standing around poking and proding with no results. :-[ ??? Oh yeah, it's a C15 Caterpillar engine. Thanks for any help.

Alan_Reagan

Sounds like the ECM connector might be loose or dirty. I'm not a CAT mechanic so you'll have to get with one of them for the correct terminology. If the CAT is like the Cummins with the gauges controlled by the ECM, then a dirty or loose connector could cause the problem you are having. Also, the voltage regulation is controlled electronically by the PCM or ECM (ECM if I remember right). I'm surprised at no codes, but that would lead me to think that it's the connector going to the gauges that is causing the problem. As far as the alternator being hot, that's not abnormal. Look across the battery leads though and measure the voltage. Measuring 200 volts, you may have had it on AC and not realized it. You should measure about 13.6 with the engine running and the voltage regulation working properly.

Mexstan

As Smoke Dog says. Could be any of those things. Also check the voltage at the battery. When you eventually resolve this problem I would not be surprised that the culprit is just a bad ground.<br>Keep us posted on the fix.

MikeyB

Check the grounding. I have seen bad grounding cause these same issues.<br><br>MikeyB

Monty

I agree. Check the ground first. There should be a couple of ground studs on the frame rail. Start from the battery box and work your way up making sure all ground studs are tight. Also, if it has the Freightliner battery cable terminals. Make sure they are not stacked wrong. I have seen alot of wierd things happen just because the terminals were not stacked from large to small. Be sure and check the tightness of the battery studs. They should be tightened no more than 10ft. lbs. If this does not help. Then check the ECM plug on the C15. I dont know if your mechanic has a schematic of the bulkhead for the ECM, if he does, trace the ground wire out in the bulkhead. Be careful not to poke any foreign object to far down into the pins. As they will spread easily. Check all pins and make sure they are pushed all the way into the bulkhead and not spread. Ohm from the ground pin to the frame rail and see what you get. I am sure there are more than one ground pin on the bulkhead, so make sure they are all covered. As Alan said, check for a loose connection to the ECM or for any dirt in the bulkhead socket. While your at it, dab a little dielectric grease on the socket. Hope this helps. Let us know.

bneaves

Also check ground studs under the dash that are spot welded into the firewall of the cab. Remove nuts and all leads to those studs, clean and re-install WITHOUT any corrosion inhibitor or and star-type washers.

spitzair

Hi guys, <br>Thanks for all the relpies so far. I'm still stumped stupid. We took the whole truck and checked EVERY SINGLE ground and lead! We left NOTHING alone. Then we drove around. Everything was normal. The voltage coming out of the alternator was a steady 14.8 while running and 12.9 with the engine off. This morning, after about 15 minutes, problem comes back! Did some more poking and proding, nothing. Still no codes or anything. ??? I didn't check the temperature of the alternator this morning, but yesterday it was so hot you couldn't touch it. So, I think the next time this happens I'll be doing an alternator transplant. Thanks so much for all the input so far.<br>

Dojman

Might try taking the belts off the alt. and turning it by hand to if it turns free. I dont guess its making any unusual noises? If your prior readings were taken correctly, I would watch the alt. pretty close. I personally would have also checked those grounds first. Open or intermittent grounds can make you wanna pull your hair out. : You might just have to &quot;run'er out&quot; and see what eventually gives

rattle_rattle

Close encounter! Check your rear view mirror!

mac1

I have worked on a few C-15's and the ecm will log high voltage or any other sensor that reads out of range. If your alt put out 200 volts the ECM would shut down to protect itself. Usually the gauges are seperate from the Cat ECM. The truck manufacture installs its own gauges. This is not always the case. The C15's I work on are in large logging trucks and they get fairly beat up, but the engine keeps pulling hard. I agree with the other reply's about the wiring and grounds, will be a hard one to find until it acts up. The ecm logges all harmful and abusive events for ever, or until the technician gets two passwords from Cat to clear them. Take a inductive type amp meter and read the amperage that the alternator is putting out. With the engine running and no other accessory turned on and assuming the batteries are fully charge and in good condition 10-30 amps would be the norm. <br><br><br>Malcolm

spitzair

Hi Guys,<br>The problem has disappeared now! We checked absolutely everything you guys mentioned and found nothing. Maybe we fixed the problem without knowing it. It's been problem free for a few days now and hopefully that keeps up! Thanks for all the suggestions and helpful hints. They're most appreciated. I'll let everyone know as soon and/or if it happens again...<br>Thanks.