BAC Forum
General Boards => Technical Support => Topic started by: Mike Gineris on October 26, 2022, 05:13:40 PM
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1999 Contessa Naples, 3126 CAT. Key switch no longer turns the engine over. This is a new problem. The RV has driven well up to now. Engine starts from remote in rear of coach but as soon as I attach one of the two wires shown in the photo, the engine quits. I've struggled with a short that drains the chassis batteries for quite some time. What are the two wires for? The transmission panel is not activated so I can't shift. I clearly have a short and maybe a solenoid issue? I'll add photos after this. The RV has been under repair fixing the entire inside for a few years. I'm gonna use it to temporarily live in during our home construction but I can't drive it. Big Problem if I can't move the RV!
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Mike
Not sure which wires youn are referring to at the batteries but I can tell you this at the batteries there should be two wire feeds which have inline fuses in them one feeds the Caterpillar ECM and the other feeds the Allison Automatic transmission TCM
Now let's start with your no start situation when starting from the drivers position with the ignition in the run position do you have any activity at the transmission shift pad (does it show an N for natural) if not the engine won't crank .
When the rear service switch is set for rear start the signal from the TCM is not needed or bypassed this is why it will start from the rear start position and not the front.
The first thing to do is check the inline fuses at the battery bay if the TCM fuse is blown the TCM will be no functional and will not provide the neutral safety function and prevent the engine from cranking.
If that fuse continues to blow you may have a short somewhere in the transmission circuit.
In the coach assist you will find a Allison trouble shooting manual to help trouble shoot the problem.
Hope this helps
Eric
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The two wires are shown in the second picture upper right corner attached to the negative terminal. Remember I have both unattached at the moment because the engine shuts off if one of them is attached. There is one in-line fuse a foot away from the positive terminal and it's ok. No other fuses are local to the bay.
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Are the inline fuses both coming from the positive side? I do have two smaller lines attached on the positive side.
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No activity at the transmission shift pad with the key on. Turning the key to start gets no response.
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Yes both the inline fuses should have 12 volts + and there fore should be connected to the positive terminal on the chassis battery.
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Sorry,...dumb question about the fuse coming from the positive side. I will look for the other fuse when I get home.
Does anyone know what the two lines are for on the negative side...I know one of those has a short problem.
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Mike check for power cat those fuses first if the fuses are good and you have 12 volts get through them then we will move on the the VIM module and check the fuses in it .
The VIM or vehicle interface module is the black box mounted in the electrical bay below the drivers station.
The VIM module has two fuses in it to get to and check them you have to remove the front cover of the black plastic module box.
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I know the module and can check it too. Can't thank you enough. Will respond later after work.
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Mike
According to the 96 Patriot wiring diagrams the ECM and TCM both have grounds connected to the chassis battery
When you say short are you referring to a small draw all the time or a draw large enough to cause an ark when you connect or disconnect the wire.
The Cat ECMs do have small a parasitic load that over a period of a month or so will deplete the chassis batteries but it is normal .
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No arc when connecting the two lines on the negative side. Right now both of them are disconnected. So the two positive lines have two matching negative lines...makes sense. OK. I will do some checking and connecting and get back after work.
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Good luck
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Mike,
It may not be related, but I have had a no start issue a couple of times and it turned out to be the main wiring harness plug located behind the electric panel on the drivers front. The first time it happened I pulled both of the harness plugs apart and cleaned them with electrical contact cleaner and properly sized fuel jet drills and mig welding tip wires. I didn't have any more issues for about 3 years. Then one day it wouldn't crank again. This time I just grabbed and wiggled the plug and it has been working for over a year that way. Hopefully your problem can be as simple.
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It worked! All I needed was to understand what the two wires were for and that there was two positive and two negative. When I put in the new batteries (drained dead by the same wires), I connected them wrong. No blown fuses. It really helps to understand what I’m looking at! Thank you very much!
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Mike
Glad you got it sorted out.
The Cat ECM draw is a problem with these coaches on some of the earlier models there was no provision made to charge the chassis battery except a very small solar panel or the engine alternator.
On or around late1999 or 2000 they ( Beaver) installed an Echo charger to allow the inverter to charged the chassis batteries From the inverter when the coach was plugged in .
On my coach I installed the Magnum battery combiner which does the same function but also allows you to adjust the voltages at which it cuts in or out .
For the time being to avoid the chassis battery drain you can use the chassis battery disconnect ( if equiped ) or if the coach is plugged in with the inverter charging the coach batteries simply connect the chassis batteries to the coach batteries temporarily with booster cables that will allow the charger to maintain both battery banks together.
The links below will give you some more information on operation and installation
https://www.donrowe.com/xantrex-82-0123-01-digital-echo-charge-p/82-0123-01.htm?gclid=CjwKCAjw2OiaBhBSEiwAh2ZSP4KhSjKz-6cQ6aQtRbaZ6fcOF41Fi4kP09qpejV2kV-8mknMYf39mBoCyWwQAvD_BwE
https://www.donrowe.com/Magnum-Energy-ME-SBC-Smart-Battery-Combiner-p/me-sbc.htm?gclid=CjwKCAjw2OiaBhBSEiwAh2ZSP3XvtYVw3SqCpStCofPRzC_No5MHtNwgdBLpTLwQPv1FJ2eGxLEJDBoCm0oQAvD_BwE
Hope this helps
Eric
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It certainly helps. There's no available external power at the moment so I'll go with the disconnect switch. Thanks very much for the details. I will research what configuration I have and get this fixed in the long run. I think I have the echo charger.
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The solar panels do well keeping the house batteries from draining but do you think the battery combiner would work to trickle charge the chassis batteries when the coach is unplugged?
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Yep
If you have the inverter charging the coach batteries the combiner will connect the two banks any time a charge voltage ( above the set limit is present ) on either battery bank .
So if the alternator is charging it should combine and charge the house bank from the chassis bank.
Or when the inverter is charging the house batteries it should combine and charge the chassis batteries
The same holds true of the solar if the solar charge controller manages to raise the coach batteries above the combiners threshold Voltage then the combiner should connect the to battery banks and everybody gets charged.
I'm not to sure the Echo charger works in both directions but I know the Magnum battery combiner does it also has a provision to allow you to use a solenoid to give the system higher current capabilities on my coach I connected it to the boost solenoid to achieve this feature.
Eric
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OK...then I will get the Magnum. Sounds like a perfect addition. My Boost Button doesn't work. There's a solenoid (or fuse) that may be out?
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Mike
For the boost solenoid it is mounted on the firewall under the bed it is the large black solenoid on the driver's side top .
Below it is a smaller latching solenoid which is run by the salesman switch by the front door.
The original boost solenoid is a White Rodgers part
To check the solenoid have someone hold the boost switch and check at the small terminals on the solenoid one is ground and the other is feed from the boost switch .if there is power and ground at the boost solenoid there should be an audible cluck when the solenoid activates if no cluck then the solenoids coil is likely burnt out if there is a cluck then the coil is working and the problem is likely the contacts within the solenoid are burnt and not making a connection.
If you have no power and ground to activate the solenoid you'll have to check at the switch and wiring to the switch
Here's a link to solenoid for reference
https://www.amazon.ca/Emerson-586-105111-DC-Power-Solenoid/dp/B003HEG8J8/ref=asc_df_B003HEG8J8/?tag=googleshopc0c-20&linkCode=df0&hvadid=292938317187&hvpos=&hvnetw=g&hvrand=10889662380013686232&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9000653&hvtargid=pla-404268119487&psc=1&language=en_CA
Hope this helps
Eric
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Will get on it. Thanks for the quick very detailed response.
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Mike
In my earlier post I forgot to mention that the boost switch gets it's power from the house 12 volt fuse panel in the bedroom