looking for some info. on my 92 dodge diesel.I seem to have a power pulsation that is related to the rpm's of the engine.the lower the rpm's the slower the pulse the faster rpm's the faster the pulse.When the engine is at idle the lights almost look like i am turning the lights on and off manually. Any suggestions as to where to start would be appriciated.

 

Just to be sure, you have an "electrical" power problem?...
If I assume correctly, does your voltmeter fluctuate with the pulses? Could be the regulator, but they are controlled by the ECM...all other electrical circuits working normally?...

 

I have bypassed the ecm and put in a regular regulator, thought that was the problem(computer), but was not.Had the alternater tested seemed fine at the time, but was not acting up while testing.I also ran another body ground from the battery to no avail.I have had some advice as to blown alternator diodes. What do you all think? And can you buy the diodes seperatly and do a self installation

 

This does not sound right. Not the way diodes would act. Better pull a wire on the regulator and see if it does it with the altinator not operating. Might check the heater relays or the headlight circuit, just guessing here. Diodes do not blink and the cycle rate would be too slow for an altinator related problem. Only possible chance is that some AC is getting past the diodes and causing the regulator to do this, I have never ever seen that happen though.

Looks like a simple check though, you eliminated the regulator (ECM) and if it does it with the altinator disconnected it is not the charging system, if it does not do it the altinator is at fault.

I have never tired to get parts for this altinator but a good rebuild shop should be able to sell you a set.

 

Is not one of the functions of the Diodes to change AC to DC?...if there is a bad Diode would that AC wave not cause this power cycling...?
Perhaps test the alt again?

 

[quote author=Craig93 link=board=13;threadid=20896;start=0#msg196136 date=1066018423]
Is not one of the functions of the Diodes to change AC to DC?...if there is a bad Diode would that AC wave not cause this power cycling...?
Perhaps test the alt again?
[/quote]

The AC would be around 400 cps or to be proper HZ which would make more of a buzzing than anything else and just not charge properly.

 

the power flicker seems to only begin when the engine is hot .this would tell me it is not a ground problem..Am i correct.

 

That is a fair assumption, a ground is either good or it's not and is not effected by temperature.

Sounds like you've got a unique situation there....have you tried the suggestions by Haulin in Dixie?

 

i think i would be looking for a component breaking down due to heat and producing a high resistence short to ground

 

This may or may not help but I will try to answer atleast on eof your questions. Diodes aloow current to pass in 1 direction only. The will not allow current to flow in the wrong direction(perfect world). They usually short out and then open(which is almost at the same moment in time). Capacitors store energy like a battery and basically tries to keep a ckt voltage at a specific level. Diodes are most often used in power regulation/filters. The zener is set up to pass both sides of alternating current, while filtering and regulating the voltage it is passing. Capacitors, inductors and or resistors are used in the ckt depending on time constants needed or how much ripple to remove. Noise filters going south are where the noise on signal lines come from(the buzzing dixie refered too) and can interefer with a ckts ability to cleanly do its job. Signal needed is also a factor of this design and just all depends on what your trying to achieve. Power pulsations like your can come from faulty brush clearances or the riggings are loose or improperly set(spring tension, gap, etc.) or ckts that are slowly dying. Resistors seem to be the most effected by heat and can change resistances in between cooling and heating up. Diodes in my experience just fail as do capacitors. The ECm/PCM are chalk full of switching ckts that use the diode theory to operate and can sometimes change value with temperature. Grounds are not as simple as Craig93 might think(no offense). Corrosion, tightness and other factors can increase the resistance at grounding bonds/straps. You want less than a ohm for your grounds(almost a dead short is great). High resistance at ground is bad for signals going into a computer. When your talking about signals of 8 to 5 volts and at times much less, bad connections(grounds/connectors) will shut down certain portions of or the entire computer. Depending on if it is the main power or just a branch. Your lights going on and off in rythym with the RPM's leads me to a capacitive scenario(sometimes broke downwire insulation) or brushes. With all that said, I have no clue but will look into my tech stuff when I get home tonight. I have the prints and stuff there and am useless without them. I don't have much experience with truck stuff yet but do this type work for the Navy and just need to look at those ckts. Good luck and I'll get back to you with more. For all those that have been helping you, I aint trying to step on toes or have doubts about how correct you guys are. Just getting my 2 cents in and hoping we can help out. ;D

 

If a ground is good, it should remain a good ground and not be effected by the temp. If the ground is not good...it is not good.period.

 

Fletch, I have asked around the shop amd looked at my books. The answers that I am getting are like what you have already. The alternator and regulator. Other electrical sources like the light heaters, intake air heaters and block heaters. The ECM being bypassed has me wandering how much of the ECM you bypassed and how you did that? Heat, humidity and othre environmentals can play havoc with electrical connections. Making them appear good at one instant and bad at others. Which always seems to be the case when you get someone to look at it and everything works great and then on the way home it starts again. I would look into some of the mechanical sources also. Belt tensioners stick, bearings in alternators/regulators, and parts of the fuel system. Problems like yours(gremlins) can be real hard to figure out but when you do find them. It is the I could have had a V8 kinda feeling(simple and something you should hace found but missed). Look at the batteries for dead cells and all your connections again. Heat palys a very important part in the failure of electrical components and may be very erroneous and in my 16 years with the electrical/electronic world, it is almost never cut and dry. (PERIOD) I would love to know of any symptoms you may not have already told us about or if any have changed. If you have done any more tests/work on this problem, would you get back to us with that information. I just hate to leave you hanging and will be looking for some more information to help you out. Good luck and God bless!

 

Here's my .2 cents disconnect battery while truck is running see what happens.

Sittenbull

 

For clarity, this is the heat I am referring to, not heat from electrical resistance in a circuit or component.

Any progress Fletch?

 

Hey Guys I have found the problem. It was a coroded and burnt accesory power lead. I took the burnt factory lead off, replaced it, hooked the ecm back up and it is working fine. I brought it in to my mechanic and got the code cleared, every thing is fine now. Thanks for all your help. Now I can go on my moose hunting trip this weekend with no worries. Thanks again for your help