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wilson8ford · 07-29-2018, 04:07 PM

Just returned from a weekend outing. On the way out, I had to make an intense stop--driver ahead decided at the last minuted to make a turn without warning or signal--intense breaking but still had three or four car lengths. After I let off the brake, the low water warning light came on--the rv's not mine! After a minute or so, it went off. Then continued to come on intermittently. The water in the reservoir is half way between the max and min, where it has been for some time. I told the wife that I'd research this when I got home. Wow, page after page of problems with low water warning lights. This is on a 2001 Winnebago, Freightliner, CAT 330 , 3126B engine, with the plastic reservoir on top of the radiator on the passenger side. If anyone has any experience with this, I guess I have several questions:

1. After removing the bed and platform, is the sensor accessible? As many times as I've been in the engine compartment, I've never had a reason to pay close attention to the reservoir. Several people report some success with cleaning the sensor, but if it's difficult to get to, would it be better just to replace it? If this sensor is disconnected (I know, not a good idea, but to maybe get through the next short trip) will that keep the light off, or does it need to be grounded? Would that confuse the computer?

2. How difficult is it to remove the whole reservoir; I'd liker to clean it. Some people report that the plastic is brittle and easy to break, it's been in use about 17 years; so. I'd sure like to avoid breaking it.

3. Other people with Cummins engines report that the low water warning leads to a gradual engine shut down to avoid engine damage. Do 3126 CAT engines do the same thing? On this next short trip in a couple of weeks, I'd like to avoid being stranded along the interstate.

Thanks,
Claude

Skip426 · 07-29-2018, 05:29 PM

I've got the side rad so , I can't help with location info .

But ; I would say fill to the max cold line , will probably help.

I've had two situations of overheating in 8 years of ownership , but never allowed the condition long enough to get to the de-rate power stage. There is a warning light in the dash for de-rate : I don't know if the warning light bar is the same in your coach , but on mine it's the lower line , to the right of the " wait to start " labeled " engine protect ".

There is a chart in this pdf that tells of the conditions that will de-rate engine power ( engine protect mode ); and I don't see low coolant warning listed.

JaminSamin · 07-29-2018, 09:13 PM

I’m pretty sure this is the sensor your looking for, With the bed and platform removed it should be easy to reach.

Arch Hoagland · 07-29-2018, 09:18 PM

"the rv's not mine"

Have you talked to the owner? Perhaps it's an ongoing problem.

wilson8ford · 08-19-2018, 11:27 AM

Thanks for the replies, but here's the now situation. I replaced the sensor, for a Cat sensor the price was about $25. I purchased the rv from the original owner and his tech, who came to help answer questions, said the rv had Shell Rotella ELC. I know Freightliner techs warn against using anything but SCA coolants, but this rv had the ELC coolant and i never had any problem in two years and sever thousand miles until three weeks ago as described in the original post.

Well, I tested the old sensor in 50/50 Rotella and in concentrated Rotellait and it worked, it showed continuity in both solutions. At any rate, I replaced the sensor. On this weeikend's trip, same results--the low water warning light would come on, stay on for varying lengths of time from a few seconds to a few minutes. So I decided to put a jumper in the connector; after all, if continuity is all it needed a jumper ought to show full water. But the rv behaved the same. The low water warning light came on for varying lengths of time the same as if it was connected to the sensor. So I conclude that the problem is not the sensor but must lie someplace else. I called Freightliner and the tech could only say that there must be a wiring issue, well that sure helped--not. The tech said that if the light stayed on a certain length of time, it would shut the engine down, but as Skip426 pointed out, there's nothing in the service manual that shows that this condition would stop the engine. I know this happens in some makes and models, but I'm not sure about this rv. Any suggestion would be helpful.

Is there a wiring diagram for this engine?

Skip426 · 08-20-2018, 07:38 PM

Did F/L help line mention a low coolant module ?
Possible defective.

EDIT : I know that F/L no longer has diagrams and schematics available online for my year of coach ; luckily I got them 8 years ago .
I have run into issues with the side rad vs rear rad wiring info being different , and National Vs Newmar for that matter ; but if you can't get what you need from F/L . PM me and I'll send you what I've got.

Skip426 · 08-20-2018, 08:06 PM

OK

The pdf I posted does not agree with the engine owners manual I have for my coach .
The chart in the original manual lists a code 62 , that isn't in the chart in the pdf and says engine shut down possible . I'll see if I can get a good scan of the page and post it.
From the schematics the low coolant module reports to the VDC and the VDC is linked on the data buss to the ECM.
Sorry for the miss information.

wilson8ford · 08-21-2018, 03:34 PM

This afternoon, Tuesday, I began trying to track down the aberrant low water warning problem. The reservoir is full, so that as a source is eliminated. Skip426 suggested checking the Coolant Level Module and sent me a set of wiring diagrams. Sure enough the diagrams show a CLM; however, after searching an hour or so, I could not find the device. I called FL to make sure that this model had a CLM, and the tech confirmed that there was one on there. I drug out the ol' creeper and checked the frame rail--there's just no telling where the builders mount things, but no CLM. Back on top, I began tracing wires when I saw a wire snake down the driver side of the engine. So I got the light and followed the wire. There behind the exhaust, about 1/3 melted was the CLM. I suppose at some time the bracket broke and let the device fall down behind the manifold. I found a new one and have it on the way. Whew, it's a relief to get that under control.

A hearty thanks to all to responded to this issue, especially Skip426.

Skip426 · 08-21-2018, 06:23 PM

Glad to be of some help .

Still working on a readable copy of my engine owners manual with all the codes for our engines , I'll post when I " get er done. "

If your CLM is like mine take that length of wire and mount it some place safe.