| Author | Message | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 654 Registered: 10-2004 Posted From: 216.9.250.97 Rating: N/A |
What is the "correct" way to find out what a single wire that is hot, is draining in amps? I have been told different ways and want to do this once! Ace | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 64 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
Ace, I have a small meter that is just placed over the wire in question, it reads any draw and how much.>>>Dan | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 168 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
You need an Amp Clamp meter like this one... http://www.calright.com/pd_987.aspx . | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 627 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
Ace, the clamp on meters are probably the easiest. If you have a small volt, ohm, amp meter, set the meter to the amp setting. Disconnect the wire you want to check and connect the amp meter in series with the wire you disconnected. If you do not get a reading, reverse the test leads from the meter. Make sure the meter is set for amps and not milliamps for the iniatal reading. | ||
| Chris Peters (Chris_85_rts)
Registered Member Username: Chris_85_rts Post Number: 49 Registered: 11-2006 Posted From: 66.194.150.45 Rating: N/A |
Followup to Jacks post: Most small cheap ohm meters will only measure small currents, say less than 10 amps. If you are measuring something like an AC unit or water heater, you will need to be sure the meter can support that current or you will fry the meter. A clamp on meter is typical safe to measure any current draw. | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 134 Registered: 12-2000 Posted From: 75.89.17.43 Rating: N/A |
Most clamp on ammeters are AC only (for the current measurement) Make sure you get one that is AC/DC amps. | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1068 Registered: 12-2000 Posted From: 74.12.87.79 Rating: N/A |
Those good folks at Fluke will have a meter that will do it all, for a price.... happy coaching! buswarrior | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 171 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
If you want a meter you can permanently install, go to http://www.mcmaster.com/ and search for panel meters.  | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 172 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
Or you can get one from WW Granger. http://www.grainger.com/Grainger/wwg/productIndex.shtml?originalValue=meter&L2=Digital+Mul timeter&operator=prodIndexRefinementSearch&L1=Meters%2C . | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 659 Registered: 10-2004 Posted From: 70.220.239.75 Rating: N/A |
Ok I have that part figured out with all the helpful hints I received from you guys but NOW what I would like to know is, is there a simple tool to check single DC wires to see if they are broken or shorted someplace where they cannot be seen or reached? In other words, how can I trace a single wire from point "A" to point "B" and make sure it is in good condition. What I believe I have is a drain going from the batteries to the ECM which has been determined to be one of two single 10g wires that each have a 15amp blade type inline fuse! Remove the fuse/s and no drain. Install the fuse/s and major drain overnight which ultimately brings on those nasty irritating codes and shut downs! I can NOW keep my batteries from discharging while sitting idle by simply removing these two 15amp fuses, but that's just a band-aid and I want to correct the problem! If the ECM is shorted out internally, that could be as much as $1500.00 (OUCH)! Thanks again... Ace | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 629 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
Ace, This is the only thing I can think of, but it might work and will not hurt anything. Can you disconnect these wires at the ECU? If you can, disconnect at the ECU, make sure the fuses are in and check the voltage at the end where the wire connects to the battery then check it at the end that plugs into the ECU. Use a digital meter so you can measure down to a tenth or better yet a hundredh of a volt. Voltage drop means a problem in the wire.(there will probably be a very slight volage drop but it should be very minimal) You might also disconnect the wire from the ECU and connect an ampmeter in series at the battery end of the wire. You should show zero amps. Hopefully, others will have some other suggestions. Jack (Message edited by JackConrad on September 12, 2007) | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 78 Registered: 1-2007 Posted From: 65.61.96.82 Rating: N/A |
Ace, Does the wiring diagram say both of those wires should be hot with the engine shut down? I can see one hot lead to the ECM to keep internal memory alive. Is it possible that something is not being disconnected as it should when shut down? Don't have a DDEC, just a suggestion. If you follow Jack's suggestions it should tell you if the ECM is drawing to much current as long as there is supposed to be B+ on both of those circuits. If it still draws current with the ECM unplugged, then those wires may be feeding something else. Just a shot in the dark, if you now have a clamp tester, check the alternator and any thing else you can 'clamp' in the engine bay. The B+ from the ECM may be back-feeding to something else. A meter in line will tell you which way current is flowing. Good luck, Don 4107 | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 173 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
My thinking is along with Don's. Is there supposed to be power on those lines when the ignition is turned off? If not it may be in the ignition switch. If these are power leads to the ECM and need to have power at all times then maybe the ECM is not being turned off by another "trigger line". . | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 660 Registered: 10-2004 Posted From: 70.221.118.6 Rating: N/A |
OK here is how I'm told this works. The ECM has power to it ALL the time. That is why it is hard wired directly to the batteries. The amp draw on it from the batteries is supposed to be no more than 1/2 amp so I'm told. I feel that the amp draw on mine is more than that causing the batteries or at least one of them, to drain down low enough that it causes the ECM to send out codes from all the different sensors relating to low voltage even though the bus will start and run ok! Like I said, these two fused wires go to the ECM somehow and end up in the center top harness connection. When this harness is unplugged from the ECM there is very little drain. Hmm, it could be the ECM is shorting out internally and not the wires at all! If I plug in the harness on the ECM there is a drain at the battery connection of these two fused wires. It arcs when making the connection and the meter says so also. For the time being, I am just removing the 2 15amp blade fuses to keep the batteries from draining! The saga WILL continue but tonight is bluegrass JAM night at the market! Thanks... Ace | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1069 Registered: 12-2000 Posted From: 74.12.72.138 Rating: N/A |
According to the DD dealer guys I know, they say it is fairly rare to have a DDEC ECM fail. They get lots sent back claiming failure that prove to be fine. Misdiagnosed wiring problems (internal corrosion being the big evil) and bad sensors are the more likely culprits. Keep on with the diagnosis, Ace. It seems that the odds are on wiring, etc, not the ECM. happy coaching! buswarrior | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 663 Registered: 10-2004 Posted From: 70.221.118.6 Rating: N/A |
Let's hope so anyway!  Ace | ||
| Jack Campbell (Blue_goose)
Registered Member Username: Blue_goose Post Number: 42 Registered: 5-2007 Posted From: 71.101.55.168 Rating: N/A |
If you pull the fuse and connect the amp meter there it will show how much curent the unit is pulling. Put one lead in one side and the other in the other side where you pulled the fuse. Again like Jack said make sure it is on amps and Mil. amps. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 634 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
Ace, Do as Jack Campbell said. If you get no reading, switch test leads. Jack | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 664 Registered: 10-2004 Posted From: 70.220.193.189 Rating: N/A |
I pulled the fuses and attempted to get a reading on the volt meter. I had it set on amps and got a reading of something like 110.? and it counted downward. Thinking this wasn't right I reversed the leads and got the same thing. Still stumped! Manny came over today and I showed him everything I had done and we proceeded to try some different things. One was to disconnect the harness from the ecm and check the voltage at the batteries inside each of the fuse holders. Both read 12.5 volts. Each battery read 12.5 volts as well and did the two cables that make up the 24 volts. After seeing that the fuse holders were good, we inserted the fuses and we went to the harness that plugs into the ecm and checked the connections there by inserting red lead in each hole and grounding black lead to frame. We got 12.5 volts in each hole that actually had a wire. One or two of them were blank and got no reading! OK I THINK this tells me that the wires are good and not shorted anywhere between the batteries and the ecm. Am I correct in thinking this? Now when I put the harness back into the ecm and then connect either fuse back into either fuse holder, it/they will arc, just as they do when the fuses are in and I reconnect the single eyelet that the two fuses go to, back to the positive post of the battery. I strongly feel that my problem lies IN the ecm. Let me also add that prevost says and has always said, that before doing any welding on the coach you should disconnect the ecm. My coach had been welded on before I purchased it as they installed the trailer hitch prior to my purchase. Knowing the firm I purchased it from, I don't think they would have disconnected anything to do what they had to do. Again, it was welded on when I installed the hangers/braces for my tanks. Now thinking back, maybe I could have done the damage myself when this was done. I really don't think I have a sensor problem or a bad wire at this time. What I REALLY need is to know where to find the serial number for my motor which is a 8V92. DD says it is on a tag right below the water pump. Well guess what, it isn't there! It could have been removed when the motor was rebuilt but if it was, where do I go now? I need a serial number to re-program a NEW ecm. I can get "a" serial number from the pro-link but the seller told me that it, (the ecm) was changed because of a prior problem so that could mean that the serial number I am getting from the pro-link is from another 8V92 motor! Any ideas, comments, theories, plans to be near by soon, or thoughts on what or where to go next? Thanks... Ace | ||
| John Lacey (Junkman42)
Registered Member Username: Junkman42 Post Number: 15 Registered: 3-2007 Posted From: 204.49.140.140 Rating: N/A |
Ace, some electronics have capacitors on the power input leads. When You disconnect the power the caps bleed down and upon recconect they pull current as they charge. If You connect a milliamp meter across the fuse leads and the meter peaks at some current and then starts decreasing I would assume that the reason is that there is a capacitor charging. The current should stabilize at a steady level as soon as the capacitor charges. John | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 79 Registered: 1-2007 Posted From: 65.61.96.82 Rating: N/A |
Ace, A few things to think about. The arc and the 'surge' that you see when you hook up the fuses/meter are filter capacitors in the ECM charging. They are part of the power supply built into the ECM. Sounds like a normal condition. Are you sure that both wires should be hot with the engine shut down? I still think it is odd that there are two hot leads to the ECM when the engine is not running. The schematic should help to determine this. The other thing that would help a bunch is another coach with the same or similar system. I would pursue this since I assume that when the engine is running that everything appears normal, ie the ECM is working. I agree with you, I would not go by the serial number in the ECM. If it has been replaced it may be the wrong ECM or wrong program for your application and thus the draining problem. Is it possible that Prevost could tell you what the original engine and ECM were? You said that 1/2 amp is normal draw. That should read on your meter as .500 or 500 milliamps. Add up the draw on both wires. That would equal a 12 amp drain in 24 hours. If I recall you said your start batteries may be getting weak. Would not take many days even with good batteries to draw them down at 12 amps per day if you are not plugged in. Is this draining problem something new? Could you let the coach set for a week and still start it before? Is it possible that the whole problem is weak start batteries? Is it possible that something else that is powered by the start batteries is also drawing current? Something plugged into a cigarette lighter or such? Good luck getting it ironed out. Don 4107 | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 665 Registered: 10-2004 Posted From: 70.220.193.189 Rating: N/A |
Yea the capacitor theories makes sense as it brought back memories of my electric RC car days. I remember having them do the same thing back then! As for the two leads being hot and going to the ecm? This is the way it was when I bought the bus and just took it that it was supposed to be this way. There is NO wiring schematic for THESE wires from Prevost as rightfully so. I guess because it is a DD part that were actually talking about. It's a pretty simple set of wires going from the batteries directly to the ecm and they are routed thru a split loom that measure approximately 10 feet from end to end. The problem is the ecm side has the plug that fits the ecm so making a new set of wires would be a little difficult for me anyway! I guess I could order a NEW complete wire harness from DD IF they supply such a thing! As for the batteries? They are fully charged at this point but have found that they DO stay UP pretty good while sitting idle as long as I remove the fuses from those two ecm wires! As long as they stay up, I can start the bus and it would probably run perfectly fine from here to wherever I choose but as soon as I leave the fuses in, the batteries, or let me say I found out, only the ONE battery, that the fused wires are connected to will drain overnight to a point where the bus will STILL start and run but evidently not supply enough voltage to the ecm which evidently supplies voltage to the 3 major sensors (low water level, low oil pressure, and high temp) that will cause an engine shutdown! Had I known before that it is only ONE battery being drained due to it's the only one that has the fused wires connected, I could have just switched those wires to another single battery and went on. Eventually from running, the low battery would be charged and evened out! It's still a band aid pulling the fuses just to keep the batteries from draining and that's why I want to trace the problem and fix it right! Yes I can keep it running and no codes but it took this long to diagnose what I have to do to keep it running. I want to diagnose what I have to do to FIX it! Thanks... Ace Also to add an answer to Don about if there could be anything else that could be draining the batteries such as a cigarette lighter etc.? The answer is NO! There is another 30 amp accessory fuse that is also hard wired into the batteries and it was removed when all accessories were removed! There is only a factory digital clock and the 30 amp fuse worked that and any interior lights that were removed along with the radio! It is completely separate from the ECM fused wires! Thanks... | ||
| Jack Campbell (Blue_goose)
Registered Member Username: Blue_goose Post Number: 44 Registered: 5-2007 Posted From: 71.101.55.168 Rating: N/A |
Why don't you give me a call, maybe I can help with your problem. We live close and my cell number is in my profile. Jack | ||
| Don Evans (Doninwa)
Registered Member Username: Doninwa Post Number: 80 Registered: 1-2007 Posted From: 65.61.96.82 Rating: N/A |
Ace, you need to find out what the ECM is actually drawing for current. Remove one fuse at a time and measure the continuous amp draw with a known good meter. Add the two together and let us know what the total amp draw is. If it is 1/2 amp as you said was normal and your fully charged batteries will not supply that over night and still function you need some new start batteries. If that draw is normal you only have three choices. Keep it plugged in with some type of charger maintaining the start batteries. Install and use a battery disconnect if there is not one. Drive the bus every couple days (with good batteries) to keep them charged. Does every DDEC equipped rig have a battery disconnect? If not and they have this kind of continuous draw there must be a lot of DDEC rigs with dead batteries. | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 135 Registered: 12-2000 Posted From: 151.213.160.43 Rating: N/A |
I don't know squat about DDEC but a half amp seems like a very high current just to keep the memory alive. 5 milliamps would be more like it. Len | ||
| niles steckbauer (Niles500)
Registered Member Username: Niles500 Post Number: 776 Registered: 11-2004 Posted From: 72.91.168.92 Rating: N/A |
Ace - how many, and what type, start batt's do you have hooked up? The ECM is taken off the center tap, correct? | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 667 Registered: 10-2004 Posted From: 75.200.240.152 Rating: N/A |
Thanks everyone for the help! I haven't worked on THAT part this weekend. I just had to get away from it for a day or so! Clearing the cobwebs so to speak! I WAS busy working on the entry steps and final hand rail. If it's ever one thing I DON'T want to tackle again is a hand rail! Well a curved one anyway. The straight ones are easy enough but forget the curved ones! I should have it installed and stained by end of this week and will post some more pics! I wouldn't have had to go thru this IF my friend NILES would have come thru with the one he has in his bus but he surely forgot... Oh HI Niles! Niles I have 4 group 31's to start the bus. The ecm wire harness is what I have found to be in the center top plug. There are two large plugs on the bottom that are held in with a 3/8 bolt. There are 3 smaller plugs along the top, right above the other two large ones and they are simply snapped into place and the middle plug is the power TO the ecm coming FROM a direct connection of ONE 12v battery! Don, there IS a battery cut-off switch but it does NOT cut off the power going to the ecm as it is hard wired directly to a positive post of ONE of the four batteries. The battery cut off switches are actually two separate. One for 12v and one for 24v and neither cut power to the ecm. Yes I know what my choices are and a friend with an almost identitcal bus even had to install a battery charger to keep his batteries up to snuff. I can do this but I would really try and FIX the problem more so that just putting a band-aid on it, if you know what I mean! Len, the 5 amp draw is what I am getting from DD. Now whether or not this is a fact or just someones fly by night answer, I couldn't tell you without further asking or deeper researching in which I am in the process of doing this coming week! Jack Campbell, thanks! I just may take you up on your offer if your still available. Are you free any day this coming week besides Monday? Ace | ||
| Jack Campbell (Blue_goose)
Registered Member Username: Blue_goose Post Number: 45 Registered: 5-2007 Posted From: 71.101.55.168 Rating: N/A |
The offer is still there, I never know when I will be here. Just call and if I am home will be glad to help. I don't have a manual on the DD2, but I think you said that you did. I have one on the 3 and 4. You shouldn't be drawing 5 amps on stand by. In your manual check the parts number and see if you have a 12 or 24 volt ecm. I wouldn't think they would put a 12 volt ecm in a 24 volt bus. | ||
| niles steckbauer (Niles500)
Registered Member Username: Niles500 Post Number: 777 Registered: 11-2004 Posted From: 71.43.39.156 Rating: N/A |
Ace - I didn't forget - I'm still using it - you were supposed to find me a deal on a matching new extra long left handed J-couch, and then I wouldn't need the brass rail (its not curved anyway) - I'm glad you didn't wait cause your install looks better On the other prob - My guess is you have 1 bad batt (I know you've checked them, but ...... another "load test" on each would be in order -JMO) - or the center tap on your batts may be connected wrong - if you need the schematic on the batt wiring send me your address and I'll mail you a copy (not clear enough to scan or fax) - HTH | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 670 Registered: 10-2004 Posted From: 216.9.250.97 Rating: N/A |
Niles, I figured since the guys at CDB's said you had a year long outstanding unpaid food and beer tab that it might take a while for you to get out of the pokey and I really wanted some sort of hand rail before then! By the way, thanks, the food and beer was great! LOL Ace | ||
| niles steckbauer (Niles500)
Registered Member Username: Niles500 Post Number: 778 Registered: 11-2004 Posted From: 72.91.168.92 Rating: N/A |
Darn - quit that - now I know where those unsigned tabs came from - BTW it hasn't been a year .... YET! | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 674 Registered: 10-2004 Posted From: 216.9.250.102 Rating: N/A |
$32,493.17 to date! Sure seems like it's been a year! Now when I look back, that WAS a lot of beer! Oh wait, maybe it was the dancer that one night! Heck we still have a couple more months left so.... LET'S PARTY! Everyone is invited to CDB,S complimets of Niles! Ace |