Community Forums

PyrateSilly · 08-04-2013, 11:20 AM

Turn the coach on and the tach seems fine, no jumping. Start to go about 500 to 800 rpm and the tach starts jumping. At the same time the volt needle also pulses, it's a little pulse but it's there. If the brakes or lights or any extra load is added it stops jumping and pulsing. Take the load off and it goes right back to jumping.
Alternator and voltage regulator both have been tested and are fine. The battery isolator has been tested fine too. If you take the tach out of the loop the volt needle will start to pulse at the same point so it seems the tach is fine too.
Thom has added a ground from the tach to the frame, battery to the frame, volt meter to the frame, and alternator to the frame. He has gone thru and cleaned and/or fixed just about every ground we can find, even those not connected to the tachometer.

Now what could be causing it and how to fix it? Those are the questions that we just cannot seem to find the answer to right now, hopefully there are some on here that can help us figure this out.

EDIT: I just wanted to add that you guys/girls on here have been great helping us and everyone else with problems, we really appreciate all the suggestions and comments.

Gorlininc · 08-04-2013, 01:38 PM

The gauge grounds are all daisy chained to a single ground. It sounds like the ground needs cleaning.

Moonrover · 08-04-2013, 02:54 PM

Is the coach diesel or gasoline? If gasoline, then plug wiring loom may be producing an arc somewhere due to a cracked wire covering. That freak signal may be creating spikes in the two gauges. Another fix might be simply installing a resistor in the pickup line. Here is a video for that:

http://m.youtube.com/watch?feature=r...&v=-6j3glUtecY

But if your engine is diesel, then there will not be plug wires, or coil, etc. Can you locate the pickup (sender) for the tach? Check there for loose connection, and cracked wire covering. I have the same jumpy tach situation. All grounding is now clean and tight. Still jumpy. Next move was to get under the engine to spray brake cleaner on the tach pickup/sender located between transmission and engine. That is the culprit in my case, but I need a lot more cleaning to see where the wiring is bad. I may just snip out a large section of wire and replace with new.

PyrateSilly · 08-04-2013, 11:21 PM

Grounds have been checked. All grounds have been cleaned. Some grounds have even been replaced and others added. Wires have been traced and if any have shown being pinched or cracked or in any way not quite right then Thom has replaced them. Still the problem of the jumping tach and pulsing volt needle.

nodine · 08-05-2013, 03:51 AM

Quote:

Originally Posted by PyrateSilly

Grounds have been checked. All grounds have been cleaned. Some grounds have even been replaced and others added. Wires have been traced and if any have shown being pinched or cracked or in any way not quite right then Thom has replaced them. Still the problem of the jumping tach and pulsing volt needle.

Do you have a system like the B.I.R.D. that connects the house charging system to the chassis charging system? If you do there could be a problem there. May be as simple as replacing the Big Boy contactor.

Bob

norwestie · 08-05-2013, 08:32 AM

My Dynasty recently had a dead tach and wasn't charging the batteries, on a year old alternator. After the tech removed the alternator, he found the big cable that goes to the batteries had massive amounts of corrosion. The cable had gotten so hot that the alternator stub melted off.

PyrateSilly · 08-07-2013, 04:48 PM

I sent this exact question off to Monaco and this is response I got back. I will have to wait till Thom gets home to find out the answers to the questions they asked but thought I would give the answer here so far from them:

"Is there anything else charging? Solar panel, gen running? Sometimes if the alternator sees a voltage higher than what it is putting out it will start to drop out and putting a load on it will bring it back. Beyond that, you have us stumped.
Frank Phillips
Technical Advisor"

PyrateSilly · 09-10-2013, 08:12 PM

Ok, I know long time posting but we just got back from our vacation about 2 weeks ago so we finally was able to unhook from shore to see if that took care of the jumping/pulsing tach and no it did not. I emailed Monaco again to see if they had come up with anything for us to try.
This is the email I got from them: "Try putting a 300 ohm or so resister between the send and ground posts on the tach, one of the other techs brought this up at a meeting the other day, I had forgotten about this."
Thom and I then went to Radio Shack and got a 330 ohm 1/2 watt resistor. Thom put it where they suggested. We then again unhooked from shore and started it up. Let it warm up and no more tach jumping/pulsing. I think we have FINALLY solved the problem. Only thing left to test would be a long test drive and unless things go wrong then then I think we are good to go.

Hutchtrans · 09-10-2013, 11:15 PM

For what its worth, The first I noticed of my problem was the tach jumping also. The end result was no tail lights , no tach and no front step. Here is a link to my recent mess. http://www.irv2.com/forums/f115/no-r...ts-175001.html

My coach is a 95 Dynasty, so it may be related.

Hutch

PyrateSilly · 09-11-2013, 06:46 AM

One of the things we did do was take apart the break lights and all on the back thinking that maybe just maybe there was a problem there. Nope, all was good but we still cleaned everything and did general maintenance on the off chance something was wrong. We went over pretty much all wires to verify connections and/or grounds which is why we could not figure out the reason for the problem. Monaco's suggestion seems to be the solution.
I asked Thom why it would fix it and he said that the resistor puts enough of a load on the line that it keeps it from pulsing and evens it out. Since it seems to work Thom will now go and take apart that area to put the resistor in there with heatshrink and to make it more stable.

walt2137 · 09-12-2013, 10:28 AM

Quote:

Originally Posted by PyrateSilly

Turn the coach on and the tach seems fine, no jumping. Start to go about 500 to 800 rpm and the tach starts jumping. At the same time the volt needle also pulses, it's a little pulse but it's there. If the brakes or lights or any extra load is added it stops jumping and pulsing. Take the load off and it goes right back to jumping.
Alternator and voltage regulator both have been tested and are fine. The battery isolator has been tested fine too. If you take the tach out of the loop the volt needle will start to pulse at the same point so it seems the tach is fine too.
Thom has added a ground from the tach to the frame, battery to the frame, volt meter to the frame, and alternator to the frame. He has gone thru and cleaned and/or fixed just about every ground we can find, even those not connected to the tachometer.

Now what could be causing it and how to fix it? Those are the questions that we just cannot seem to find the answer to right now, hopefully there are some on here that can help us figure this out.

EDIT: I just wanted to add that you guys/girls on here have been great helping us and everyone else with problems, we really appreciate all the suggestions and comments.

Jumping tac when not plugged to shore power and engine running is generally a indication of the alternator going out on the pre computer Cummins engines.

PyrateSilly · 09-12-2013, 11:28 AM

Alternator has been tested and it is going strong. That is why it was confusing to everyone. Fix is working well. Thom made the connections with the resistor and send and ground posts more secure and heat shrinked it so that it just won't fall out and it will be a little hard for dust or water to get in there.

Oh I heard back from Cummins and their response was for us to take the coach to a service center ------ in Alaska. We are in SoCal at the moment.

EDIT:
Would we have done that first before anything else? NO!! We cleaned and fixed all grounds and wires every where that we could. We tested everything and/or took it to be tested. We were at our wits end trying to figure this out. Some on here have said that they are "just living" with the tach jumping/pulsing. Thom cannot do that and will fix things if they are not doing what they are supposed to be doing. So we contacted Monaco (yes they are now a different company) and Cummins to see what they could suggest. Monaco's techs gave a suggestion and we tried it and it works right now. Thom is happy and that makes me happy. People on here say "Happy wife, happy life" well when it comes to the coach and it running right for me it's "Happy Thom, happy wife"