floydfowler

OK I checked the voltages at the alternator terminals: Alternator: There should be no voltage between the alternator + and – terminals either with the key on or off unless the engine is running. If voltage is present check the connections to the battery isolator and the functionality of the isolator if connected properly. With ign. off, I read -12V ., with ign. on, read - 12V Ignition Terminal: There should be no voltage to the ignition terminal with the key off. There should be 12V to the terminal with the key on (with or without the engine running).With ign. off, I read -0.311 V and with ign on, I read -12 V between ign terminal and negative alternator terminal and 12.2 volts between ing terminal and chassis ground. DUVAC Terminal: The DUVAC terminal requires 12V (coach battery voltage) to function, this functions as the “battery sense.” Depending on the application this may be 12 V with key on as some vehicles have a relay with the ignition system. I read 0 v with ign off and -.15 v with ign on. from duvac terminal to negative alternator terminal but I also read 12.8v between duvac and chassis ground. It is obvious the the negative alternator terminal is not grounded to the chassis.

Rich is really a prince of a guy!! Yes, this does help me to get all of this into focus. I had just confirmed that the white ground wire going to the center terminal is connected to chassis ground and took resistance readings between the terminals of the green relay with the wires disconnected as instructed yesterday by Rich Today I got different readings from those given to Rich as follows: Pos test lead to center terminal and neg lead to lower terminal I get 0.59 m ohms, and with neg lead to top terminal I get "open". With neg test lead on center post and pos lead to lower post I get open, and with pos lead to top post also open. The trouble shooting info you referred me to refers to the Battery Isolator testing with ohm meter says I should be seeing zero or near zero ohms to both battery terminals with neg lead on center post but I am seeing the chassis post (top) as open. It also indicated that the terminal 1 (center??) should be connected to the alternator but my center terminal is connected to chassis ground. I am going back out to the coach now to recheck the voltage readings at the alternator as outlined in the tips.

Excellent information! I am going to recheck "green relay" with ohmmeter and confirm the readings. I was curious as to why I would have the Lambert LE 415 as a charger when the inverter seems to be doing all the charging.

Very interesting information. I wonder if I have the Bird relay. I am going to crawl around in the underside compartment where the inverter is located to see if I can find one. I have noticed for some time that the alternator light on the dash flickers with the voltage about 14v. I found that I could stop the flickering by turning on the headlights to add load and the voltage would drop to about 13.5v. Now wondering if all of this is related. Thanks for sharing this information.

Zero amp on both wires. I guess I should have checked them before I killed the power and removed the wires. I will turn ref and inverter on i the morning and draw the batteries down and try again.

Positive on center post negative on lower post I read .134 m ohms. Neg on top post I read open. Neg on center and pos on lower post I read.03 m ohms, neg on center post and pos on top post I read open. before I took wires off, green led was on indicating charging. Replacing wires and turning shore power back on no green light. DW is calling me as it is almost 6;30 in Mooresville NC and she says wine time has started without me! I will get any other readings you want i the morning. Many thanks for all of you guy's help. Floyd

Yes I have a GE clamp on ammeter. Where were you wanting a reading?

I know the relay works with the aux power switch. How do I check the green box? A little more trivia.... I took it out for a test drive for about 1 1/2 hours with the refrigerator and inverter on. Inverter showed negative 38 amps. As soon as I got it parked I switched to shore power and turned ref off. Inverter/charger display shows Bulk charge at + 90 amps. In about 20 minutes it switched to Absorb charge at 60 amps. In 10 minutes it is down to absorb at 50 amps and I read 40 amps at the house cutoff switch. This is why I am thinking the Duvac system is not working properly since the house batteries don't seem to be charging from the 160 amp alternator. I know the alternator has the capacity to offset the 38 amp inverter draw.😬

If the photos are ok for you I can send you a photo of all that I have. The wiring diagrams are in the back of the HR Manual that came with the coach.

.The chassis wiring diagram is in two parts. Coach is all on one page. I was expecting the alternator to charge the house batteries at about the same rate that the inverter was discharging them (38a).

2001 Holiday Rambler Imperial with cummings 350 ISC

I thought this was the "combiner relay" that was used to boost the chassis battery with the house because it clicks in when I push the aux start switch. I guess it has more than one function. The alternator is keeping the chassis battery charged while running but not the house batteries with the inverter drawing 36 to 38 amps. That chassis wire from the alternator is the one I can't find. I have checked the amperage and voltage at the alternator but don't know where it goes from the alternator. Not sure if I am stepping on any toes by using this thread. Should I start a new one?

I thought that device was a battery maintainer (Lambert 415) that trickle charges the batteries while on shore power. Here is a wiring diagram from panel door and my wiring diagram drawing.

I am having the same problem on my 2001 Holiday Rambler. I have tried to find the isolator but the large guage wire from the battery post on the alternator disappears into a mass of plastic wire loom and I have yet to be able to locate the isolator. The inverter is pulling about 36 amps with the refrigerator running but the alternator is only showing about 12 to 14 amps at 14 volts with the engine at idle so I don't think the house batteries are getting charged. I checked the voltage on the Duvac terminal with engine off but ignition on and it is showing 12V. I found a good 20 a fuse in the duvac circuit and a battery isolator lockout relay but I think that is for the battery isolator relay which is activated by the battery boost switch on the dash and used to combine house and chassis batteries for starting with weak chassis batteries. I don't know if it is also used for the duvac . I have a wiring diagram for the coach and it shows the ign. and Duvac wiring but only a post for the battery connection and no wiring diagram! So, at this point I am stumped and would appreciate any suggestions.

I have only one window and it goes from 6 to 2 when turn on the exhaust brake, and downshifts twice as I am slowing down. Good news! I finally studied the wiring diagram ( with a magnifying glass as the print is tiny) and was able to locate two Omron 7866 relays for the exhaust brake in the front panel. I switched then with two borrowed from other positions (panel has 5 or 6 of the same relay) and took the coach for a test drive. Turbo boost works fine now after using the exhaust brake. One or both of the relays was sticking and both are now in the trash with four more coming from Amazon. We are ready to hit the road again!😋😎 Many thanks for your time and assistance!

Not sure. When I turn brake on, it stays in 6 until coach slows down and then downshifts. Slowing more and it will downshift again. I will need to get it on the road again to get your answers but I will not be able to do that until Sunday. Thanks for your reply. Floyd

Still lose turbo boost after using exhaust brake! The new PacBrake works great but after turning it on,slowing down and turning it off, I still have no boost pressure and the engine has zero power. I finally convinced the DW to ride in the back with the access cover open to observe the brake actuator cylinder. She confirmed that the cylinder actuates the exhaust brake but when I turn the brake off the cylinder does not open the brake. I have tested the air switch/solenoid and I know it is operating properly. I must pull over and put coach in neutral and set park brake. After a few seconds, I can depress the accelerator and see that boost pressure is back working. Drive on fine as long I don't use exhaust brake. I am thinking the problem lies somewhere with an electrical switch, relay or sensor. I think I have a throttle position sensor that overrides the exhaust brake if the throttle is depressed. Whatever the problem, when I turn the brake off, the solenoid isn't getting the signal to release the brake. It is also tied in to the Alison transmission somehow. I am not getting any codes. A wiring diagram for Pac Brake circuit for 2001 Holiday Rambler with Cummings ISC 350 would be most helpful if anyone has such a thing. 😞

UPDATE Good news! waste gate rotates very freely though only for about 30 degrees. Bad news, "e" retaining ring left the planet when I finally got it off. Looks like about 1/4" ring but I'll try to get caliper on the shaft to be sure. Also, reattaching actuator arm is a real pain from underneath the coach. I should have the new pac brake on by Thursday and can't wait to test drive it.

Opps, I see Rich has already covered that!

Thanks for all the good information. I have soaked the gate shaft and connections with penetrating oil and will have a go at moving it tomorrow. If I should need a new turbo (HX40 w) can I install it as it is delivered or is there special adjustment needed?

Rich, Sounds like what I assumed to be a vacuum diaphragm is actually a pressure diaphragm/module.

Thanks Rich. The exhaust brake moves very freely when I apply power to the solenoid, in fact, it snaps back and forth with momentary 12v applied so I'm thinking it is releasing. I have lube from Pac brake coming with the new pacbrake. Still wondering about the diaphragm actuated internal waste gate on the turbo. I have soaked it with penetrating oil and will try to get it moving by disconnecting the linkage.What is the purpose of the waste gate?

I have a question about the Holset HX 40W turbo. What is the function of the internal waste gate? I have posted about my problem of losing boost pressure after using the exhaust brake. I have ordered a new brake from Pacbrake which supposedly has much better braking performance although I followed posted advice and tested the old one by powering the 12v solenoid and confirming the arm snapped on and off freely. I am now wondering if my problem could be this diaphragm actuated waste gate. I tried unsuccessfully to rotate it by hand but have not removed the linkage yet to try it again. I have also removed the front inlet duct on the turbine and confirmed the shaft has no perceivable side or end play. After using exhaust, engine loses all power and boost pressure and I see black smoke from exhaust. I can pull over for a few minutes and all is good to go again!

And mine as well. Looking back on my dilemma at the rest area, I had a bad chassis disconnect switch but chassis battery was fine so when I used the boost/bridge switch I was only drawing the 8 or 9 amps from the house batteries that normally flowed through the chassis disconnect switch when starting engine!! Mystery Solved!! Many thanks to all who contributed! You guys are awesome.😁

Thank you Sir! This starter wiring diagram confirms my theory.