False High Temp Alarm on Cummins 6B Recon

[Ted Bumgardner]

I have a pair of Cummins 6b Recon engines (DOM 09/28/15) on a 42′ Hershine that I purchased about a year ago. The engines have about 100 hrs on them.  A problem has developed where I am getting a High Temp Alarm on the port engine when the running temp shows about 175F.  I have confirmed the gage temp and the engine temp with an IR gun and find them to consistently read within 5F degrees of each other, so I am fairly confident this is not an overheating problem but a high temp alarm problem.  The problem does not occur on the stbd engine, only port.  I also have high exhaust temp alarms that are not triggered – only the high temp alarm on the lower helm console for the port engine.  The lower helm console has a Cummins control center (analog) with Beede Gages. I have checked and confirmed the ground at the port instrument panel (0.4-0.6 Ω), I have changed out the circuit board to a new one from Seaboard Marine, I have cleaned all blade connections at the circuit board, temp gage, and sending unit and re-set with dielectric grease.

And still, I get a High Temp Alarm on the port instrument panel when the gage and the IR confirm the port engine is running at about 175F.

Any recommendations?

Topic

[Ted Bumgardner]

High Temp Alarm Problem Solved

I purchased the SBMarine high temp alarm switch, adapter and buzzer for each engine, installed and bypassed the PCB, but disconnected the high temp lights on factory panel and wired them into my new high temp alarm set up.  They work perfectly. When I put a jumper on each high temp switch, the new alarm sounds and the factory high temp light goes off just as it should.  I also bought the 160 Stats, but haven’t installed them yet.  I am going to keep an eye on my temps and decide later if I need the 160s.  For now, everything seems to be working great. Thanks again Rob.

[Ted Bumgardner]

High Temp Alarm Problem Solved

I purchased the SBMarine high temp alarm switch, adapter and buzzer for each engine, installed and bypassed the PCB, but disconnected the high temp lights on factory panel and wired them into my new high temp alarm set up.  They work perfectly. When I put a jumper on each high temp switch, the new alarm sounds and the factory high temp light goes off just as it should.  I also bought the 160 Stats, but haven’t installed them yet.  I am going to keep an eye on my temps and decide later if I need the 160s.  For now, everything seems to be working great.

Thanks again Rob.

[Rob Schepis]

Not sure on the higher readings at the fwd section of the ex manifold.

Did you hit all these areas and those are the only hot spots?

IR Gun Temperature Check

I know you have been through a bunch of hot and cold cycles but wondering if there could be an air trap issue?  Have you ever brought her up to temp with the caps loose?

Have you considered switching to the 160 deg F tstats?

1 user thanked author for this post.

Mike Uliasz

[Ted Bumgardner]

Rob, I took the boat out today to run it and see if I could get the temp up and see if I am getting the High Temp alarm on one or both engines.  After warm up, then running at around 1500 rpm for about a half hour to get up to operating temp, I then bumped up to 2000 rpm for about 15 min. I got high temp alarms on both engine control centers.  More intermittent on Port, more consistent on Stbd. My IR when scanning the top of the tank was 186F on both engines.  Scans of the exhaust manifold toward the back of the engine was less, however IR scan of the exhaust manifold forward of the manifold cap showed temps of around 205F on Stbd and 202F on Port. The gauges both showed temps in the 185F range. 

Question: Should I be concerned with the higher IR temp at the front of the exhaust manifold?  

If the IR temps seem to be within spec, I think I will proceed with installing a  new High Temp alarm using the SB adapter off the manifold cap.  I discovered that I can disconnect the tan wire from the temp gage to the PCB without it triggering an alarm – So, I think I could disconnect the PCB from the temp gauge and run another alarm, from a new temp alarm switch and connect to the high temp dash light. This would be redundant with the gauges and their temp sensor, but would be intendant of the PCB.   

As long as the high IR reading I was getting on the forward end of the exhaust manifold is not indication that I have an overheating problem. 

Any thoughts or recommendations/

Thanks,

Ted

 

 

[Ted Bumgardner]

Problem follows PCB

Rob, thanks for the recommendation, great idea and easily done.  So, this morning, I put the new PCB on the Stbd engine, and put the old PCB from the Stbd Engine to Port.  I started a timer, did initial warm up at idle, then moved up to 1200 rpm, while tied up in the slip. Then I documented the gage temp, and IR temp at 30 min increments.  At 40 min, the Starboard engine high temp alarm went off at about 175F gage temp. So, the problem seems to follow the PCB.  No idea why the new PCB is alarming at 175F. The engine temps stabilized at 175 and quit climbing, at least in the slip while running at 1200 rpm in 55F water.   Next is a running test where I do basically the same thing with the engines under load and running at a higher rpm. I haven’t seen the running temp go past about 190F at 2000 rpm.  Looking at my log, I have seen an occasional and brief High Temp alarm on both engines, with the gages and IR confirmation around 190F.  The predominant problem has been the port alarm, which is now serving the starboard engine and seems the problem has now moved to the starboard engine when I moved the PCB.  I now want see if I can determine if I get false high temps on the other engine when running hard. I don’t know what thermostats are in these, but by looking at where the temp quits rising is seems they are likely 175F T-stats. 

Looking at the paperwork that came with the boat, I see that the VDO gages may have been changed to Beede gages when the 6BT Recons were installed along with all new gages, analog control centers, new SS tanks, transmissions, helms, and basically all mechanical and electrical gear in the engine room including wiring harness, were all installed new the same time at 100 operating hours ago.  I purchased the boat at 50 hrs, and the high temp alarm starting showing up at about 90 hrs. When the high temp alarm problem started up, I had the heat exchanger camera’d, the impeller inspected, the coolant flushed, etc. But everything looks new upon inspection.

Since the PCB works off the temp gage, is there a potential that the PCB is miss-reading the temp and setting off the alarm due to the PCB being attached to the Beede gages and not  VDO gages?

Is there a multi-meter reading that I can take at the temp gage to see if the correct signal is going to the PCB?   The gage reading seems to align with the IR, so I don’t think its a gage or sending unit problem. 

Any and all suggestions are appreciated.

[Rob Schepis]

Normally that suggests a PCB issue but you are saying the one that is throwing the alarm is the new one?  Since this is a twin screw, may be worth the effort to swap P&S for further diagnosis/elimination.

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