My dash tachometer quit working. It will go back and forth when the key is turned on but stays on 0 when the engine is started.
The tach on my Silverleaf works fine. Do the get their signal from different places.
The '99 get the tach signal from the ecm same as silverleaf. Is the hour meter still working on the tach?
Don't know but will check.
Same with ours... I haven't gotten around to fixing it yet but you are welcome to beat me to it, as long as you share the answer! If the ISC in our 99' U270 gets the tach signal from the ECM as Craneman (Chuck) says the ISM does, I would suspect the tach. But the fact that it does the full sweep when turning the key on makes think otherwise... it will be interesting to see what you find out.
Don
Several years ago the tach on my '99 u320, which is only slightly younger than yours, exhibited the symptoms you describe (the engine hours did not increase). After many hundred dollars worth of diagnostics at MoT and Allison (where MoT referred me) the gauge still did not work. I decided to purchase the Silverleaf VMSpc and ignore the gauge on the dash. I have gone that route for at least five or six years. Last fall, after several forum members had reported great results having gauges repaired at Lauderdale marine, I decided to ship the tach off to them in Florida. They checked it out and said that there was nothing wrong with the gauge itself (same thing MoT had said years earlier). I have since been told that the sensor for the tach on my coach is on the M-11 engine rather than the transmission or the alternator. I understand that it is hidden below the air conditioner compressor. I have yet to actually find or see the sensor but one of these days will get ambitious and find it and replace it, then my dash gauge may work again. Until then I am content to live with the VMSpc display. Quite frankly, a tach on an automatic transmission coach with engine and transmission computer controlled safeguards, is rather superfluous.
Richard
Jan, I beg to disagree. You are right in the flatlands, but I find the tach critical for mountain driving.
Would any of the schematics show the wire coming to the tach? Not my forte and I am missing some schematics. Sometime in the past I called FT and when they asked me to look at a drawing number, I didn't have it so they emailed it to me.
I did some searching and the info I come up with is the tachometer sensor sends a signal to the ecm. Can't find any information about a sensor that goes directly to the front of the coach.
Therein seems to lie the crux of the situation. Why does my (and other people's) VMSpc tach and engine hour meter work perfectly but not my dash gauge? The gauge has been checked twice and the wiring from the dash to the rear of the coach, according to MoT, is good.
The VMSpc can get info only from the ECM. So how does the tachometer gauge receive input that is different from the VMSpc?
I have no wiring diagrams which address this kind of detail.
Richard
The answer may lie in the fact that there are 2 sensors in the pickup and when both fail the light comes on, maybe the tach signal is coming from one and the other goes to the diagnostic plug. Just a guess but seems possible.
Craneman, thank you. You say it is a fact that there are two sensors in the pickup. No one that I have talked with has mentioned that fact. That may very well explain why the tachometer gauge on the dash and the diagnostic plug which feeds the VMSpc are getting different info. Your information may spur me to investigate this further.
Thanks again.
Richard
One of my sensors was oil soaked and the symptom was an erratic idle. My tach always worked. If the other side had failed would the tach not work but the motor idle perfectly?
Part was inexpensive and external. ISM I understand has a harder to fail newer design.
If you replace the sensor and your tach works that must have been it?
I read about the two sensors in a previous post on the forum. I can see from pictures of the pickup, four wires.
Craneman I went out yesterday and found the sensor. I believe mine has four wires coming out of it which would be 2 senors.
I don't have time to do anymore trouble shooting right now as I'm getting ready to go away. As I have a tach working on the
Silverleaf I'm fine for now.
I stand corrected 4 wires. Changed the post with the wrong number
buy Position Sensor 2872362 for Cummins L10 M11 N14 Engine (https://www.fridayparts.com/position-sensor-2872362-for-cummins-l10-m11-n14-engine?gclid=EAIaIQobChMIoqms1Mig6wIVg8DICh1z9g7TEAQYASABEgIJP_D_BwE)
Thanks for the link Chuck. I just ordered mine. I will figure out exactly where it goes once I have it and get back to my coach.
Richard
Richard,
Here is a link to a post that has some pics. that may help you out on your search.
No start, nor CEL Please Advise (https://www.foreforums.com/index.php?topic=25678.msg203833#msg203833)
Mike
I pulled my sensor this morning, it takes less than 5 minutes and takes a 11/16th open end wrench. I checked the continuity in mine
and the 2 outer wires had continuity and the 2 middle ones had continuity, so I'm not sure that is the problem. As the Silverleaf
tach works I will leave it for now. Thanks for the advice Craneman it sure made it easier.
Wonder if that is 17MM instead of 11/16"???
Metric on a twenty year old Cummins engine?
Don't know, but 11/16" is NOT a common inch size.
Easy enough for someone to slip a 17MM wrench on it. 17MM is just a touch smaller than 11/16", but a very common metric size.
Inquiring minds want to know.
It probably could be as the engine is metric. Over the years I have used 11/16th a lot as 7/16th nuts use 11/16th wrench and the bolts
use a 5/8th wrench.
I went out and checked and it is 11/16. 17 mm won't go on and 18 is too loose.
Well after a mouthful like that witworth doesn't seem so bad upon reflection, haha
Never could figure out why you needed two different sized "spanners"
Just a follow up, I replaced the sensor and the tach still doesn't work. I will keep looking for the problem when I have time.
I did the same thing a couple of weeks ago with the same results. Keep us posted as you try to sort this out. It might save me some effort when I get back to the rig.
Thanks,
Richard
SILVER LEAF LOL. Call Roger he can fix you up!
Chris
If you figure out what the signal is supposed to be at the tach, I can make up a tach generator crank trigger that will feed the OE tach.
Richard and I both have Silver leaf so that's why it's not a panic, I just like everything working
Still following. If the tach is hood and the sensor is good must be wiring? Mine doesn't work either.
I had time 2 days ago to do some checking. First the tach white wire 317 goes to the ECU C connector and 17 plug which is 3 rd. one
down and middle row. I have continuity to there. Yesterday when I checked it with a volt meter I have 4. something volts and
after I had the engine going it read 2. something volts. I don't know what that means. It still doesn't work. When I turn the key
the tach gauge does it's regular swing and then it stops at the high end of the scale.
Did the sensor fix the problem?
No. Still trying to figger it out. The odometer in the speedometer is going. Some times its there and sometimes its not.
Same here. My Speedo goes out once in a great while. The tach is out like yours. In the above wire chase it said the whit one goes to ECU? Not sensor? Is there a signal from ECU that may be the causing issue? Speedo intermittent, related. Doesn't seem like this is rocket science?
Craneman had asked if the hour meter had quit too and it has. I checked the wiring to the ECU and it seems fine. Maybe next spring or summer I might seen both gauges out as Jan suggested. Right now I have a Silver Leaf which I use as it easier to see. I just like the
gauges to work as they are there. The Silver Leaf is keeping trace of mileage.
Those gauges fail frequently(see lots of posts) and this is the common failure mode.
What is the fix? Heard on another site the wire goes to alternator and a blown fuse
The U320 doesn't get the tach signal from the alternator it gets the signal from a sensor on the front of the engine and then goes through ECU to the tach
So if u change the sensor and the gauge, is it the ECU?
I hear of a TACHS quiting. I do not heat about a lot of fixes?
If it was the ECM you would be setting on the side of the road.
There is a couple of companies that will check/repair tach if it is the problem.
Mike
Lots of speedometer shops deal with VDO so you might call one in your area and describe the symptoms, etc. The one I used in LA did a great job and had a fast turn around back in the '80's. Our U300 speedo only works part of the times so will be sending it in.
Pierce
Ecus can fail on one component, but be fine for everything else. The ECU was bad on my 98 Cummins pickup. The prob!em was the ECU had a built in alternator regulator that fails. ECU is good for everything else, but the internal regulator goes out as a common issue. I just set up an external regulator. No reason to change ECU out.
So it seems that tach failure is a common issue.
What is the fix.
Haven't heard of any fix, except maybe the sensor or the tach. Seems like I have heard more of the tach being good, and the sensor being good. So what have been the fix?
I have had my VDO gauge checked out by two different companies and both said that the gauge itself was just fine. I have replaced the sensor on the front (rear) of the engine. The gauge still does not work. My VMSpc gives flawless tach and engine hour information so the info from the sensor through the ECU apparently is working.
There is one more thing that I may investigate when I have the time and inclination to pursue it. The sensor has four wires with a short pig tail which plugs into a wiring harness. My understanding is that two wires go to the ECU and two wires likely go straight to the gauge, a redundant system. When I unplugged the old sensor, the plug had a good deal of oil intrusion. I cleaned up the plug with liberal amounts of spray contact cleaner and left it at that. When the gauge still did not work I just put this project on the back burner awaiting further inspiration.
I have since read a post here which made me think that maybe the oil had wicked up the wires inside the insulation and possibly found a weak spot in the insulation where the faint signal could short out between wires. My guess would be that this would not be too far up the wires. I may, at some point, investigate this further.
Unfortunately, I do not have an answer for you but this is where my story stands at this point.
Richard
The ECM has a "Digital Tach signal", at least that is what they call it on connector B pin 17 of the ECM and a "digital tachometer return" on pin 26 same connector. So if the sensor and tach is good, this would be the next place I would look. Still looking for ANY body that has fixed their VDO tach on near vintage 98, U320. Again, I hear a lot of broken tachs, but no fixes.
has anybody really verified where the tach wires go from the tach (other than power and ground, assuming they are good and not effecting signal from engine).
Thx!
Has anyone changed the ECM?
Did it fix the problem?
The
Larry
All four wires from the sensor go into the ECM and one wire goes from the ECM to the tach. One day someone will find the
problem I hope.
Swap ECM with someone that their tach works?
I was thinking about disconnecting battery and then disconnecting all of the connectors on the ECM. Spray them with contact cleaner and reconnect them. Fixed a lot of problems that way. Don't want to open a can of worms though. Maybe I will just do the connectors with tach in and out signals.
Larry
That might be good idea. My tach quit after I had one of the plugs off to hook up my Jake brake.
So your tach quit when you unplugged a connector on the ECM (and obviously plugged it back in)?
Thx
It didn't work after I put the Jake brake in. I don't know if that had anything to do with it or not. I didn't start the engine for a few
weeks when and after I put the Jake Brake in.
Still looking for a fix to tach not working.
Anybody?
I'm with you, still looking.
Last resort, have you "broken tach" guys considered replacing the stock instrument with a aftermarket product? Couple ideas below (I know nothing about either of them):
Electric Tachometers for Diesel Engine | 15,000 Satisfied Customers | Diesel... (https://dieselpro.com/engine-gauges-detroit-diesel-cummins/gauges-electrical-12-volts/tachometers-tacometros.html)
Search Results - Stewart Warner (https://www.stewartwarner.com/products/gauges/search-gauges/search-results/?fwp_gauge_type=tachometer&fwp_gauge_type_description=d2988ea7c8ce8560867177eed5161a0a&fwp_scale=0d098c601af0d584978a711d6894337c&fwp_diameter=93658b2385157ad9216410075b606313&fwp_bezelfinish=black&fwp_voltwattcurrent=12-v)
Could some computerized Cummins Foretravels still use a magnetic tach pickup located on engine bell housing like non-computerized engines use. The bell housing pickup wire connection can come loose.
Just a thought reinforcing Barry's suggestion. When we installed the Rostra aftermarket cruise control (on the death of my King unit) the tech discovered the signal from the top of the Allison was very weak. He pulled the magnet and found it to be worn paper thin. Replaced the magnet and greatly improved the tach signal. Might be some value in this.
Anybody have any update on a tach fix? Replaced tach, no joy. Certified wire from tach to ecu. Still thinking it could be the ECU
If the magnet or wiring is not the problem, send it in to a speedo shop. They do fast turnaround, repairing any speedo, tach or auto clock. VDO gauges are sure a lot better looking than SW stuff. I sent all my Grey Market speedos down to North Hollywood Speedometer Repair - NH Speedometer (https://www.nhspeedometer.com/) where they put the U.S. face and ODO gears in them. Fast and reasonable. Call them first and explain the problem.
Pierce.
Barry,
I don't suppose you have a picture of specifically where on the bell housing PU wire attaches? I have looked and looked but there are a lot of wires in that area on top of the bell housing.
Don
Ldillow already stated that they replaced the tach, so advice to send the tach in for repair probably not useful.
If the tach is new, and the wire from tach to ECU checks out good, then that just leaves whatever generates the signal that goes to the ECU. If you can identify and locate the source of the RPM signal as mentioned by Barry and Alan (above), try replacing it and see what happens?
New signal generator will certainly be cheaper than getting into repairing or replacing the ECU.
There is a few of us with the tach not working. As I have a Silverleaf and the tach works
with Silverleaf it isn't a priority with me as I don't look at the dash much anymore. I have
wonder if the connection on the ECU is bad as mine quit after I had the ECU connection
off when I need to add the connection for the Jake Brake when I put it in. If it was easier to
get at I would have checked it out. Maybe some day.
Don,
No photo, but the C8.3 without a computer had a single long sensor with a single wire that was bolted to near top of bell housing which could be observed by looking down at rear of engine with bed up. Bell housing is between engine and tranny. Don't think there are any other wires in this area.
Barry
Not the same, but my book shows the tach grounding through the oil pressure switch . Bad switch and the hr meter and tack dont work .
I had the wire integrity checked by cummins. From connector B pin 17 to tach, they said it was good and the proper signal is being offered to tach. They said bad tach, it is the second tach so not sure that is true. The saga continues
Fixed my tach after 2 years of trying and roughly 400 in troubleshooting costs. FT took the tach back so that helped.
There is a diagnostic button under dash cover. If it is pushed, the tach does not work.
Just that simple
Is that the button beside the button that raises and lowers the RPM, key on, engine on?
Surely it can't be that simple. Several of us here have had this issue and like you spent years and hundreds of dollars trying to resolve it. I will check my system out in the next few days and hopefully have a tach again. Thanks.
Richard
When in doubt, add a ground wire. As I said above, Mine grounds through the oil pressure switch . Grounds corrode on these old things .
I tried the button nest to the tach adjustment and nothing, the tach still not working.