Low Water Dash Warning Light..Comes on only when pull light switch.

[pcallison]

I have recently purchased a Monaco Knight 2003 cummings eng.  Discovered just a couple of days ago this problem.  Coolant level is full and have read threads about cleaning the sensor, but my confusion becomes it only appears when I turned on the headlights??  Goes off also when switch is pushed in.

Any ideas on this?  I hope that I haven't made a bad investment..

Phil

[Dr4Film]

Look for a bad ground connection somewhere in your dash area or just run a new ground wire.

[Rikadoo]

Personally i would check for a compremised ground, sounds like the circuit is backfeeding.

[pcallison]

Would that be associated with the light switch?  I am not real familiar with doing this diagnostic, but am a fast learner with guidance lol...

[vito.a]

Most Monaco diesel coaches have a grounding bus bar in the front above the generator.  I would start by cleaning all the connections on this bus bar.  If the bus bar has a main wire running from it down to the chassis, clean the end on the chassis as well. 

The problem is I'm not sure the Knight has a roll out front generator.  You may have to stand up inside there to reach it. 

Also make sure you periodically remove and clean the coolant level probe and wire connection with steel wool.  

Edited May 30, 2022 by vito.a

[pcallison]

Thanks vito.a.

Since removing the sensor may envolve some fluid loss, can it be refilled with regular ethylene glycol 50/50?  Or do I need a special blend/type.  The coolant in it now has an orangish tint.  Not the typical green I am familiar with.

 

 

[Rocketman3]

2 bits of info - I don’t know enough to know if either are revenant…

There are (at least) 2 types of coolant the old green stuff and OAT. They cannot be mixed. My understanding is the OAT is superior- but it costs more (and requires two flushes with distilled water).

When I bought my rig a few years ago, the prior owner had a new coolant sensor that had a ground. The old one did not. It would give me low coolant warnings when it was started up - he said the fix was to replace the sensor. I had the mechanic do it at the first oil change. Worked well since then.

 

Good luck!

[Rick A]

Todays humour. Just don’t drive at night or turn on the lights, or as the Brits would say, always look on the bright side of life. Of course I’m kidding, it doesn’t sound like a major issue, the obvious is earthing as stated above. Good luck you bought a good product as long as it’s in good condition. 

[Ivan K]

27 minutes ago, pcallison said:

Thanks vito.a.

Since removing the sensor may envolve some fluid loss, can it be refilled with regular ethylene glycol 50/50?  Or do I need a special blend/type.  The coolant in it now has an orangish tint.  Not the typical green I am familiar with.

 

 

Can't you siphon some out so it does not spill and then just pour it back in? That way you don't mix it with something that's not compatible. 

[Tom Cherry]

14 minutes ago, pcallison said:

Thanks vito.a.

Since removing the sensor may envolve some fluid loss, can it be refilled with regular ethylene glycol 50/50?  Or do I need a special blend/type.  The coolant in it now has an orangish tint.  Not the typical green I am familiar with.

 

 

There has been enough debate and discussion on the types of Coolant and the need for the Cummins SCA to fill a full set of the Encyclopedia Britanica.  If you are not familiar with the need for the SCA to reduce corrosion then you need to do some research.  
 

Your MH came, most likely, with the green Ethylene Glycol 50/50 (Distilled water only) mix and was a Texaco HD product.  Monaco got a kickback for listing the brand specific in the owners manual.  Again.,..read up on this.

Since then, there has been a world of updates and chemical blends and such in coolants.  

Many are running “lifetime coolants”…of various colors.  Many are still using the original green Ethylene Glycol….who knows when the environmental laws may change and kill the manufacturing of such.

Bottom line, you need to know “what” coolant is in the engine.  Any reputable OTR shop or Cummins dealer has test strips to determine the proper amount of SCA in the coolant.  There IS a range….so just popping a pint of it in is NOT recommended.  
 

My personal opinion, and I had my coolant changed…without a flush around 20K, and have it tested annually….sometimes I get the strips (they MUST not be expired and stored in some hot places and test myself.  I also figure that lifetime in Coolants is designated at maybe 200K….something few will ever see.  So, I keep it simple.

I would have it tested.  I would also look or have a tech look for a coolant filter.  Monaco put them on and then .Cummins said not needed and dropped them.  I can’t remember the year, but you MIGHT have one.  Changing that and testing the coolant would be my plan.

I agree with the posters.  You CAN, and others have done this….drill a hole and thread it in the chassis inside the Genny compartment.  Sand or clean the chassis member.  Then use a piece of #10 insulated wire and a ringed terminal and a hexwasher bolt and run your own ground.  Some have run the an additional #10 ground from the ground bar and connected it to the dash module or the ground terminal strip inside the dash.

Most LIKELY at here is a ground issue,  the idiot lights or warnings come on, at least on mine, when you GROUND OUT a sensor or circuit.

Good Luck,

here is a link to Cummins and the SCA…
https://www.cumminsfiltration.com/eme/coolantadditives
 

[jacwjames]

Not sure what type of tank and sensor you have but on my 2002 Windsor the original tank had a sensor that was inserted from the top, it was held in place with a heavy rubber grommet.  The sensor would pull in out, with a bit of force.   If this is what you have you won't loose any coolant to pull sensor out and clean but you may not have enough clearance to pull it out.  The sensor was a one wire sensor that used the coolant as a ground source.  You can check to see if it is a sensor problem by removing the wire and grounding it and see if the low coolant light goes out.

The new tank I installed had a design change with a threaded port in the side and used a Ford low coolant sensor.   This was a two wire set up but I just combined both terminals into one and connected to the existing wiring harness.

On my 2002 Windsor I have a Kysor low coolant alarm, this does rely on a 12 volt source to work.  Not sure if you have something like that or not, if you've got a wiring diagram it will show this. 

 

[pcallison]

Thanks all....No wiring diagram I am aware of yet.  I will dig deeper in the owners/maint. log....  But alas, I do believe I have found the problem or at least narrrowed it.  And anyone who has knowledge of it please share with me on if I am on the right track.

Yes on Coolant Tech.  I figure there are several, but didn't know if you could pick some up without driving an hour for my nearest RV dealer.  I can definitly  pull some off if it were to ever come down to that and everything that I have read about low coolant sensor tells me that I will have to eventually but...see next line

I believe it lies in the light switch itself causing issues.  I have just discovered that something within the switch is making the low light glow.  It is the cab dimmer.  You crank it all the way to brightest setting (ct. clockwise) and the darn thing comes on at that point.  Dim the dash where it is a low glow, and wallah, it goes off.  

Any Takers on This One? 

lol....and I don't really like driving at night anyway Rick A....and I have run without lights before back in the day lol....

BTW my sensor is at the lower level of the aluminum expansion tank mounted horizontally and single wired.  

[pcallison]

And Again, you guys have been very helpful and I greatly appreciate your time as I continue to search for more knowledge.

 

Phil