alternator gauge

[cerberusiam]

I fail to see the difference. Perhaps you would like an ociliscope so that you could see the peak values from the full wave bridge rectifier that the alternator is using to covert the AC that the alternator puts out to a very lumpy DC voltage. Using a DMM you can even see the spikes in voltage if your meter is good enough. Heavily dampend readings are the norm in this type of application.



Thanks rbattelle for researching what the service manual actually says.

Never said it wasn't normal or useful, just that the gauge is essentailly a fake representation of what is actually going on. In this whole description of all the electrical stuff, tell me how you trouble shoot the potential problem when all you have is is a heavily dampened gauge that does not show the real story?



Your missing the point of the thread, the gauge will suddenly go to zero and show errors then return to normal. It doesn't matter how the reading is generated, what matters are the failure points in between and how to determine which ones are the culprit.



The FSM description is great reading but how accurate and how useful is it? It basically says you to have to error points that the gauge will go high or low and the rest of the time its in the middle range. The FSM also states very clearly the ECU monitors engine oil pressure at all times yet all the evidence suggests the main sensor is only a switch. Not enough in-depth info to say either way if the gauges are accurrate.



The alternator will completely quit charging, to the point where the test machines fail every test, and the gauge will just go to the low side of the middle range and sit there. No lights, no codes, and it is definitely putting out less than 9 volts.



A bad battery connection will will boil the passenger side battery and even blow it up before there is any indication of problems. The gauage does NOT show excessive charging.



All these things have been documented and lamented more than once. The actual fixes for the gauge reading a problem have been:



Failed batterie(s)

Failed alternator

Failed ECU

Failed Cluster controller

Failed Cluster

Corroded battery connections

Corroded grounds

Corroded ECU connectors(s)

Other connection issues





Thats the trouble shooting list, the only question left is where to start.

 

[mwilson]

Oil pressure gauge

As you two are explaining the gauge/buss system I would like to ask the following question about my '06...



The oil pressure gauge is operated by a switch with a 6lb go/no go sending unit. I buy that.



How does the oil pressure gauge show a high reading on a cold start and then drop to normal pressure after the engine warms up??? Does the ECM use block temp and ambient air temp to establish the supposed pressure shown on the gauge???



I know if I start it at -20 zero it goes up a lot further on the scale then it will at 50 degrees on first start.



Just curious.



Mike.

 

[cerberusiam]

Thats the whole question about any of the gauges, overhead, and even the data streams off the data bus; how accurate are they really?



Any data stream can be manufactured and tweaked to be seemingly accurate and still be totally fake. One of the pros\cons of having a computer interpreting and transmitting the data.

 

[rbattelle]

Does the ECM use block temp and ambient air temp to establish the supposed pressure shown on the gauge???

In my opinion, yes. Although I've not seen the actual algorithm, I believe it's a function of water jacket temperature and engine RPM.



I think maybe some of us are confused by Cerberusiam's use of the word "fake". I don't think he means "fake" in the sense, "not real", so much as he means "not a direct analog reading. " In other words, a signal that has gone through an A/D and subsequently D/A conversion. Some of us might call it a "conditioned signal" instead, but it's really just semantics.



As Ken points out, there's no such thing as a digital voltmeter that doesn't do exactly the same thing. Maybe the right question to ask is, "how much do you trust the gauge you're looking at?" I suspect everyone has different answers to that.



Steved brings up an excellent point about the alternator brushes. Volsfan, I strongly suggest inspecting that alternator.



-Ryan

 

[cerberusiam]

I think maybe some of us are confused by Cerberusiam's use of the word "fake". I don't think he means "fake" in the sense, "not real", so much as he means "not a direct analog reading. "

No, I mean "fake" as in "not real", "bogus", "fabricated". At least as far as the gauge readings go. Everything I have tested so far on charge, oil pressure, and water temp leads me to believe the signal is fake and bears no resemblance to actual.



Funny thing is the temp readings and oil pressure readings seem close off the data stream. Not the gauges.



There is a difference between a conditioned data stream that has been converted, and, a data stream created from several interpolated sensor readings, BIG difference. It seems all the gauage readings are the result of interpolation, and not a very granular result either.

 

[rbattelle]

No, I mean "fake" as in "not real", "bogus", "fabricated". At least as far as the gauge readings go. Everything I have tested so far on charge, oil pressure, and water temp leads me to believe the signal is fake and bears no resemblance to actual.

Fair enough, but I disagree. The gauge readings are damped a bit, but otherwise accurate most of the time (except oil pressure) in my experience. I am generally aware of when they are inaccurate, so I can compensate.

Funny thing is the temp readings and oil pressure readings seem close off the data stream. Not the gauges.

I didn't realize you're able to read the PCI bus. I don't dispute your measurements as I have a different year truck and no ability to read the PCI data bus to determine the difference between it and the gauge.

There is a difference between a conditioned data stream that has been converted, and, a data stream created from several interpolated sensor readings, BIG difference. It seems all the gauage readings are the result of interpolation, and not a very granular result either.

Maybe this is where we disagree - which gauges are fed by transfer functions made up of independents from various sensors. I think only the oil pressure gauge falls into this category, but I think you're arguing that they all do. Oil pressure is the only gauge that has no corresponding analog sensor on the engine (up until 2006, anyway).



When you say "granular" do you mean "resolution?" If so, the resolution on the gauges themselves is obviously terrible. But certainly this is different from their accuracy.



I accept that I could be wrong and they're all complete fabrications on some trucks. On the one I have, it would be dishonest of me to say that anything but the oil pressure gauge is "faked" simply because I have no evidence that leads to that conclusion.



-Ryan

 

[JamesStevens]

FWIW any time I put a multimeter on either battery the volts are 14. 8



I have a edge insight and the water temp gauge on the dash and the insight are very close. I would call the water gauge on the dash accurate. If I read about the insight right it reads directly of the CAN bus, so basically what the water sensor is putting on the CAN bus.

I wish we had real oil pressure senders to read off of.

P. S If U like gauges the Insight is a great buy, I love knowing intake air temp etc... I wish I would have bought it first, could have eliminated many gauges in my truck (I have 7 + the insight!!)

James

 

[Kirwin]

Great discussion

I am of the same opinion, that the oil pressure gauge is driven by an algorithm that the PCM is running based on various sensor inputs. If oil pressure ever falls below 6 PSIG, I suspect the PCM will immediately (for all practical purposes) cause the oil pressure gauge to read 0 and that will result in a check gauges light and an audible ping from the instrument cluster. I've actually been there and got the T shirt in my 97 for this exact scenario. Long story short the oil plug backed out at 60 MPH coming down out of Yellowstone in Montana. My first indication was oil on the front of the travel trailer, while I was trying to figure out what is on the front of the trailer I glance at the dash and oil pressure is 0 psig and the oil can is lit. 97s didn't have the audible alarm remember, but did have a real oil pressure gauge. Did not matter, truck is running under load at 60 MPH pulling a 12,000 travel trailer. Not my best day!!!! So I don't think any factory gauge fake or real will help you with this. Now I run a Cyberdyne gauge on top of the dash and it flashes if oil pressure drops below 10 PSIG. (Which happens on my 03 fairly frequently as a matter of fact. ) I also have Cyberdyne gauges for coolant temperature and a switchable gauge for transmission, transfer case and rear differential temperature. I can tell you that the Cyberdyne gauge shows coolant temperature to be very close to what the dash gauge says and even responds to PCM controlled fan lock up on my 03. I can see my dash voltage gauge drop when the intake heaters cycle so I believe its sensing voltage. Sure if I'm troubleshooting a problem I'll use the Fluke 88 but for every day driving the gauges don't matter that much because when you have a problem your not going to see the gauge reading low unless you very lucky. Lets face it your not driving along starring at the dash. Its doesn't take long under load to ruin an engine with no oil pressure. How many Cummins engines have you heard of that failed due to no oil pressure due to an internal problem? Not one I'd guess. Ken Irwin

 

[cerberusiam]

I have a edge insight and the water temp gauge on the dash and the insight are very close. I would call the water gauge on the dash accurate.

All the gauges are close WHEN the actual readings are at normal. Its when they start going low or high but not tripping the set points the problems start. My experience, the gauges do not reflect readings correctly away from the norm.

How many Cummins engines have you heard of that failed due to no oil pressure due to an internal problem? Not one I'd guess. Ken Irwin

Well, hate to rain on your parade but there it is.



Dodge's fake oil pressure gage - Dodge Diesel - Diesel Truck Resource Forums



The instances of engine damage due to low and no oil pressure on the CR's is way higher than all the previous years combined. LOTS of motors being swapped and rebuilt due to this exact issue. Low oil pressure that the gauge NEVER reflects is the biggest issue. Loose an injector running down the road, push all the oil out of the crank case and replace it with diesel. Guess what low oil pressure but not low enough to cause the gauge to drop or the light to come on does to the internals?



It NEVER shows on the gauge until the engine is idled down, whereas oil pressure dropping to 20 psi when it should be 50 psi at running down the road is BIG red flag.



Staring at the dash as you suggest is reaching for excuses. Analog gauges are perfect for quick glance readings. Once you as the driver get used to seeing needles in a certain position it only takes a quick glance to register an issue IF THE GAUGES MOVE CORRECTLY.



I have caught out of range readings many times just like this, but, not with the OE ones.



Given:



Ruin an engine



Blow up a battery



Run way low on coolant



can happen before the OE gauges EVER indicate a problem doesn't not instill me with confidence.

 

[Kirwin]

So what you saying is....

cerberusiam, The fact that a injector failed and caused all the oil to be forced out of the engine is not an oil system failure. Its an issue with the quality of oil. The oiling system is working as designed. The pump is still pumping just as much oil. Yes, I understand that oil pressure will fall as the oil thins out due to fuel dilution, but that is not an oil related failure either; that is a fuel system failure and the oil pressure is merely a secondary indicator. Most people would not be able to tell this anyway even with a real gauge as the resolution on a factory instrument panel gauge is at best poor. Oil pressure in my 03 runs anywhere from about 8 psig at idle hot, to about 68 psig on a cold start. It varies significantly based on engine temperature and obviously with engine RPM. With a bad injector, by the time you noticed engine oil pressure was low based on a "real" gauge, the damage is already done. This may be a warrantable failure as determined by Chrysler but that doesn't make it the fault of the engine's oiling system or the "fake" oil pressure gage. Injectors seem more prone to failure on the CR trucks but a engine failure due to an oil system problem is very rare. The most likely cause of a oiling system failure is a clogged piston cooling nozzle due to a poor quality oil filter or allowing the tin foil seal of the oil jug to find its way into the crankcase. Note that these are not warrantable failures as it will ultimately be determined that foreign material was introduced into the crankcase causing the failure and thus the warranty claim will be rejected by Chrysler. If you want a "real" oil pressure gauge, do what most on here would do, purchase a high quality after market gauge from one of the TDRs vendors and install it. Ken Irwin

 

[cerberusiam]

cerberusiam, The fact that a injector failed and caused all the oil to be forced out of the engine is not an oil system failure. Its an issue with the quality of oil. The oiling system is working as designed.

Are you really that far out in the weeds?



Tell ya what, try this simple little test and see for yourself. Add a real gauge to your engine and note what the dash gauge says and real says at 70 mph.



Drain a quarter of the oil and replace with diesel, note your oil pressure readings again under the same conditions.



Drain a quarter of the crankcase capacity and fill with diesel, note your oil pressure readings again under the same conditions.



Drain a quarter of the crankacase capacity and fill with diesel, note your oil pressure readings again under the same conditions.



If it is still running, repeat.



When you get the damage fixed, loosen the oil filter to replicate an oil change gone bad. Now go drive until the engine seizes noting readings of both gauges.



Here is another test, get the engine temp up to close to 300 degrees and note the gauge readings.



That oil gauage not only tells you the pressure it tells the condition of your oil at a given time, which is exactly the point you keep missing. It doesn't matter what the gauges read when things are good, but, it matters greatly what they say when things are going wrong. If the gauge doesn't tell you until it is too late what good are the readings?



My point all along has been just because the gauge says its good don't make it so. Ample evidence to support that, not the opposite.

 

[Kirwin]

I understand your point.

BUT the factory oil pressure gauge is not there to tell you when a fuel injector goes south. If we wanted to guard against that, it would be better to have a oil level detector in the side of the sump as some diesels do. The fact that oil pressure drops when a failed injector squirts a continuous stream of raw fuel into the engine is not a oiling system failure. The example that you sighted above is NOT a oiling system failure. Nor is low oil pressure the primary indicator of a failed injector on the CR engines. There are plenty of examples out there of what happens when an injector fails open. The purpose of an oil pressure gauge is to measure and display oil pressure. Now oil pressure can be utilized as a general indicator to detect many engine maladies, but the primary one is OIL SYSTEM failure not a fuel system failure. As far as that goes engine oil pressure falls as bearing clearances open up over the life of any mechanical component lubricated by oil (or anything else for that matter). Oil pressure also drops with engine temperature increases, but I don't decided to add coolant by looking at the oil pressure gauge. I stand by my statement above that oil system failures on the Cummins B series engine are few and far between. The increase of injector failures resulting in severe crankcase contamination with fuel has resulted in some people believing that this is caused by the oiling system and that is not the case. As above I could fill the crankcase with water and the same result would occur. Crankcase contamination is not the oiling systems fault. I'm not saying that oil pressure won't be affected by fuel dilution, and I agree with you it would be nice if the bean counters at Chrysler wouldn't have eliminated a gauge the accurately measures and displays oil pressure. I've never tested the system by inserting another oil pressure sensor into the engine wiring harness simulating 0 psig oil pressure and seeing how long before you get the low oil pressure warning on the dash but I would bet it doesn't take too long. The way you approach this though, is that by not giving us a true oil pressure gauge we have been cheated. That's what the TDR is for!!! To inform us of these issues so that we can make informed decisions about how we operate, accessorize, and maintain our trucks. Ken Irwin

 

[rbattelle]

I stand by my statement above that oil system failures on the Cummins B series engine are few and far between.

I agree.

Frankly. if I'm diluting my crankcase with diesel fuel I doubt I'll understand that's why my oil pressure has dropped - if I even notice it's dropped. Resolution on my oil pressure gauge is something like 10 psi.

I use my oil pressure gauge to tell me the condition of the oil system. I use the dipstick to tell me the condition of the oil itself because my gauge doesn't have enough resolution and I don't have the intellectual capacity to determine oil condition from it.

-Ryan

 

[cerberusiam]

The example that you sighted above is NOT a oiling system failure.

Then by those criteria everything you used as an example is also false. By your reckoning the oiling system almost never fails. Sorry, not buying into the fairy tale. ANYTHING that impacts the oiling system is classed as oiling system failure. It doesn't matter if its a lack of oil, duluted oil, FOD in the oil, its a FAILURE still the same. Your splitting hairs on a question that is not in play as my original comment was the gauge readings are fake.

Nor is low oil pressure the primary indicator of a failed injector on the CR engines.

Never said it was, gave you two examples where it can be the primary indicator of trouble. Point is, you will never see it on the gauge until it is too late.

There are plenty of examples out there of what happens when an injector fails open.

Yep, what do you think happens when an injector failure cracks? If doesn't melt the piston, it may not even show as loss of power or a miss. It just fills the crankcase with diesel and continues on its way. Many, many, many instances of this happening as the hours increase.

The purpose of an oil pressure gauge is to measure and display oil pressure.

No, the purpose of an oil gauge is to measure the effectiveness of the oiling system. THAT is what the pressure indicates, and, its not what the pressure reads under normal conditions that is important. Its what the gauge says under abnormal circumstances that really counts. Again, my point is problems will never be seen with the OE gauge. Documented, done.

The way you approach this though, is that by not giving us a true oil pressure gauge we have been cheated.

And your NOT??



Yes, I am extremely unhappy about the lack of gauges and there lack of validity to the gauges on these trucks. I am annoyed about the amount of $$ to buy and then add the basic tools that an operator needs.



Again, you have totally missed the point of every post I have made. I just used the oil pressure gauge as an example but the same applies to all the gauges as I pointed out way back when. The readings are bogus and do not reflect what is actually going on. Thank you for making my point for me.

I don't have the intellectual capacity to determine oil condition from it.

Sorry, not buying that for a second Ryan. :-laf I KNOW your more than capable of doing just that.

 

[rbattelle]

We've gone way off topic on VolsFan. VolsFan, what's your status?

-Ryan

 

[cerberusiam]

We've gone way off topic on VolsFan.

I'm sorry. What portion of the discussion about gauge readings, their realtive validity, the potential issues than can effect their readings, and using them for diagnostic tools do you feel is "off topic"?



The topic of the thread is "alternator gauge", and, the OP clearly describes a situation where the gauge readings are intemittent and is asking how to use it to diagnose a problem or OTHER suggestions to solve his problem.



Ryan, please explain how the discussion to this point has NOT provided ideas, suggestions, and a direction for the OP to solve his problem. I believe this is a discussion forum and since we aren't to 15 pages yet and there is no vendor\gender\brand bashing why do you feel that it is "off topic"?



The only thing I see that is "off topic" is a post with a link to another thread that has ZERO bearing on the discussion here since its title is obviously not about gauges. To keep the discussion on the current subject, the poster should seriously considering removing it.

 

[rbattelle]

I'm sorry. What portion of the discussion about gauge readings, their realtive validity, the potential issues than can effect their readings, and using them for diagnostic tools do you feel is "off topic"?

All the stuff about gauges that aren't the alternator gauge.



I realize I'm as guilty of being off topic as anybody else.



-Ryan

 

[Kirwin]

We are not going to agree so....

I agree with your Ryan.



"Then by those criteria everything you used as an example is also false. By your reckoning the oiling system almost never fails. Sorry, not buying into the fairy tale. ANYTHING that impacts the oiling system is classed as oiling system failure. It doesn't matter if its a lack of oil, duluted oil, FOD in the oil, its a FAILURE still the same. Your splitting hairs on a question that is not in play as my original comment was the gauge readings are fake. "



Cerberusiam, exactly as I stated. Oil system failures on the Cummins B series engine are very rare.



The oil pressure gauge is not directly representative of actual oil pressure; but, it will tell you if the oil system fails and oil pressure drops below 6 psig. This is an oil system failure. Unless you have direct proof that the other gauges are not real, get over it. The coolant temperature gauge and the volt meter do respond as expected to changes it their monitored parameters and this has been confirmed by both mechanical gauges and observations of several others on the TDR. Every electric gauge uses analog inputs and through some process determines the gauge needle position using either an algorithm if computer based, or a set of parameters if electric. Most electric oil pressure gauges are actually volt meters that use the varying resistance of the oil pressure sender to indicate oil pressure. The volt meter is just calibrated in psig.

As I said before, the purpose of the TDR is to disseminate this type of information so that we, as the owners and operators of our trucks, can make informed choices. News flash the oil pressure gauge does not display actual oil pressure but it does indicate that the oil pressure is at least 6 psig. This means that the oil system is functioning and you are not experiencing an oil system failure. This does not mean that there is not something else wrong with your truck! Ken Irwin

 

[Prairie Dog]

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[cerberusiam]

All the stuff about gauges that aren't the alternator gauge.

Since when are comparitive examples to prove a point off topic? Thats a rather narrow mined view to take on any subject, but, since you insist that no information EXCEPT what you have perosnally discovered or interpreted, correctly or incorrectly, is valid then its a predictable attitude.

Unless you have direct proof that the other gauges are not real, get over it.

Since you don't want to accept the proof I won't bother. You know what you know and that is good enough for you. Be so kind as to NOT impose those restrictions on others.

As I said before, the purpose of the TDR is to disseminate this type of information so that we, as the owners and operators of our trucks, can make informed choices.

You are a hypocrite, plain and simple. On one hand you laud the dissemination and discussion while sanctioning repression and rejection of information and theories that do not match your own. In the end you resort to childish posturing and petulant response to challenges. Way to stay on topic. :-laf