Coolant temp gauge doesn't show any movement

[Roger Milne]

So I took the unit out for a drive and albeit not more than an hour roundtrip, but my coolant temp gauge barely registered any movement. All the other pressure and temps all read fine, but I was wondering if there's an easy way to check the gauge or if I need to replace the temp sender in the engine block?
I bought this last year and drove it for a few hours before we parked it and have lived in it for the past 8 months and if I recall it did read although it was what appeared very cool. Not in the middle of the gauge like everything else.

Any suggestions??

[Steve Huber]

Roger,
The sensor output should be a resistive value so you should be able to check the gauge by applying an open and or a ground to the gauge input and see the gauge respond. The engine coolant sensor location is shown in Coach Assist / CAT & Allison Manuals / C9 Sensor Location Diagram/Part#s.
Steve

[Roger Milne]

Oh Ok thanks Steve,

I'll see what I can do to ge the gauge off the peg and I'll go over the manuals you mentioned.

[Roger Milne]

So just a follow up on this in case it helps others.

So we just drove 2000 miles from AZ to SC. As I was a little skeptical of the gauge and it's accuracy, I was able to get in on the Aladdin system this RV has installed and actually has a sensor page much like modern cars have with temps and pressures from various components.

Thankfully this one had both Coolant and Transmission temps and the actual readings were exactly where I'd expect the temps to operate at under driving conditions.
What I will say is this. The CAT and Allison analog gauges work, but at slightly different values compared to the digital ones on the Aladdin. But they did show readings and the Allison more closely that the CAT.
The other thing I did notice is the CAT engine itself, seems to run very cool and it was only during extended hill climbs in the AZ and NM hills that it climbed to what I'd expect them to run normally. But even during continuous road driving they CAT ran about 130-150* digitally and about 1/4 the way off the peg to halfway on the analog.

This is my first experience driving a big diesel and this type of transmission and I can say it is really cool to just watch these rigs, just pull and pull, when going up hill. A very different experience from driving conventional vehicles where the RPM increases dramatically going up hills.

Can't wait to drive it more.

[Eric Maclean Co-Admin]

Roger
It sounds like it's time for new thermostats.
That would also account for the low gauge readings.
You might want to take your engine serial number and check with the Cat online parts menu to see exactly what temperature thermostat or ( regulator) in Cat terms that C9 should have in it .
If I'm not mistaken the thermostat on a C9 should be in the 180* to 190* temperature range .
Running the engine with faulty thermostats will prevent the engine from reaching proper operating temperature which contributes to poor fuel mileage and a greater possibility of wet stacking at idle not to mention poor cab heater performance in cold weather.

Hope this helps
Eric

[Roger Milne]

Roger
It sounds like it's time for new thermostats.
That would also account for the low gauge readings.
You might want to take your engine serial number and check with the Cat online parts menu to see exactly what temperature thermostat or ( regulator) in Cat terms that C9 should have in it .
If I'm not mistaken the thermostat on a C9 should be in the 180* to 190* temperature range .
Running the engine with faulty thermostats will prevent the engine from reaching proper operating temperature which contributes to poor fuel mileage and a greater possibility of wet stacking at idle not to mention poor cab heater performance in cold weather.

Hope this helps
Eric

Well I am learning a bunch about this rig and I really appreciate that info we are parked at an RV park for the next month or two while we search for a house I will do my due diligence and find me a shop that can service that and take care of that issue. good to know and I appreciate it

[Steve Huber]

Eric's correct re t'stat. The C9 is speced for a 190 degree t'stat. See attached for C9 specs.
Steve

[Joel Ashley]

I was surprised at your numbers too, Roger.  Especially given your 42’ w. tag running an engine more commonly found in shorter coaches.  Our “little” 37’ w. C9 gets warmer than you report.  Taking Eric’s advice, before too long, would be more than a good idea. 

I’ve had our rig out several times over the Rockies in late fall in snow, nailed by a sudden icy squall going over Mt. Hood to Bend, parked in Idaho Thanksgiving snow, and stuck in a sudden Wyoming plains blizzard.  You need your dash heater, though often less than great (its a long way from engine to dash), working as well as possible should you get trapped for 6-7 hours in the middle of a Wyoming freeway like we did on our maiden voyage.  Hydronics can work better, but not perhaps as concentrated on pilot and copilot, or for defrosting a windshield.

Joel

[Roger Milne]

So we are parked at an RV site for the next few weeks. We just went under contract for a new home in the local area and once we are moved in and settled,I plan on getting this rig in for some air system work and the Thermostat issue addressed. I appreciate al the input.

[Eric Maclean Co-Admin]

Roger
Good luck with your new home

Eric