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Topic: Elec Burning Smell Around Thomas Aux Compressor (Read 527 times) previous topic - next topic

Elec Burning Smell Around Thomas Aux Compressor

Hello Forum Folks,  May be developing a problem with the Thomas Aux Air Compressor.  Last night I'm watching a football game (LA-C v LasVegas)  in the coach and the little compressor kicks on as usual.  However, this time I notice a different sound, kinda like the pump is pulsating and not getting enough juice from the batteries.  I turn off the pump and then turn it back on and the sound goes away.  Today the pump comes on and it sounds normal, but I go to check on it and when I open the bay door I smell an electrical type burning smell.  That can't be good.  Get out my flashlight and examine the pump and wires.  The positive wire going to the pump appears to be burning.  This wire comes from a device at the rear of the pump motor that appears to be a coil or a solenoid.  Hoping the fix is simple, i.e., replace the wire or is there something else going on?
David & Sherry Kendrick
"Gizmo" The Doggy Lama
USAF(Ret) 1971-75; 1979-95 (20 yrs)
2003 U320 F03 [6179] 38PBDS (3/2016)
2016 Chev Silverado Z71 LTZ
Motorcade 17738
--------------------------------------
New Horizons 5W 25' RKS (1/2004 - 3/2016)
2003 Chev Silverado 2500HD Duramax
Tent (5-person) White Stag (1972 - 2003)

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #1
The wire which is overheating is obviously the power (+) wire for the motor.  A wire overheats when it is passing more current than it is designed to handle.  If the motor is binding or seizing or turning against excessive resistance it will draw more amps than normal, which will overheat the power wire.  Possibly the bearings are going out on motor or compressor is failing?

The item you have circled in red looks like a relay in the motor power circuit, which is controlled (opened or closed) by the wire coming from the pressure switch.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #2
It could also overheat if the connection is loose or strands are damaged.  With a short wire, just replace it with that or larger gauge wire.

Could it be a bad motor-- sure, but start with the easy (read that CHEAP) things first.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #3
With a short wire, just replace it with that or larger gauge wire.
Not disagreeing with your answer, but isn't that kinda like replacing a blown fuse with a bigger fuse so it won't blow?

IF (big IF) that wire is the original wire on that compressor setup, then at one time it was the correct size wire.  Now it is melting.  So I guess the big question is:  What has changed?

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #4
Not doubting your answer, but isn't that kinda like replacing a blown fuse with a bigger fuse so it won't blow?

IF (big IF) that wire is the original wire on that compressor setup, then at one time it was the correct size wire.  Now it is melting.  So I guess the question is:  What has changed?



Understand your concern.  But wire should NEVER be the "weak link"  Fuses, by definition are there to protect the wire. I know I replaced many many feet of 12 VDC wire in our Fortravel with larger gauge for lower voltage loss.  Voltage loss in a wire= resistance= HEAT.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #5
Need to look at the complete wiring diagram for that compressor power circuit, to see if the 12V power source includes a fuse.  The diagrams are not clear on that point.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #6
If the switch "passes through" the 12 VDC positive, the fuse should be before it.

If the switch merely closes a RELAY (a much better arrangement, as full voltage doesn't hammer the points in the switch) it should be before the relay.

Please do let us know what you find.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #7
Need to look at the complete wiring diagram for that compressor power circuit, to see if the 12V power source includes a fuse. 
Chuck,

The power for that motor comes off of one of the manual reset breakers in the basement hid behind the white cover. IIRC it is 15amps that powers the relay on the power side for the motor. The control side has it's own fuse.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #8
The power for that motor comes off of one of the manual reset breakers in the basement...
Mike,

Thanx.  In that case, perhaps the breaker has failed closed?  Otherwise, it should open before the power wire at the motor melts.

I found the diagram linked below in the Forum library.  Don't know if it is correct for the 2003 U320.  Can't tell if the power wire has the blade fuse holder shown as stock, or if it was added on by owner.

https://www.foreforums.com/index.php?action=media;sa=item;in=1059#viewitem

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #9
That 15 amp fuse is OEM as mine has it also.
 Diagram 95.39 that the OP posted showes that fuse.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #10
Diagram 95.39 that the OP posted shows that fuse.
Where?  I'm not seeing it.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #11
Oops, I added a 1 to that fuse but the one you posted shows it.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #12
Oops, I added a 1 to that fuse but the one you posted shows it.
But I'm not sure that is the same HWH compressor as in the original post.  The pressure control switch has a different pressure setting.

Do some of the newer coaches have two different HWH compressors?  Or different pressure switch settings for different equipment?

I don't know enough about the newer coaches...

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #13
The OP and I have the same year coach so tomorrow I'll look at my set up and see if I can find that 15 amp fuse.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #14
If you have a loose connection it can cause the wire to burn the insulation off the wire without causing the breaker to trip. See that happen all the time.  Replace the wire make good connections, then let's see what happens.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #15
Make sure the nut on top of the Essex relay where the power wire to the motor is attached is tight.  If not remove it and clean the ring terminal and the stud.  Double check the condition of the ring terminal connection while you are at it.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Elec Burning Smell Around Thomas Aux Compressor

Reply #16
Thanks for all the responses.  Went to an auto parts store for the 8AWG x 1/4" ring terminals and then to a hardware store for stranded wire.  Ops I purchased #10 wire and didn't realize my mistake until I got home.  >:(  Since my wire and terminals didn't match I decided to remove the old wiring, i.e., the easy stuff.  Should have done that first since the wiring had 5/16" terminals on the motor side and 1/4" terminals on the switch side and what appears to be 8AWG wiring.  The positive wire insulation was a little bit burned / melted near one of the ring terminals, but was IMHO still usable.  The common side showed no damage.  What I did discover was the studs on the Thomas motor were loose!! I don't know much about motors but these studs screw into the case and have a 5/16" post the wire connects to. Cleaned all the terminals and tightened up the loose connections and life is good.  The motor doesn't make any strange noises and seems to be running with increased horsepower.  I say this because it doesn't take nearly as long to bring the system up to pressure when the pump kicks on.  No telling how long the problem with loose connections has existed.  Thanks again Forum Folks.
David & Sherry Kendrick
"Gizmo" The Doggy Lama
USAF(Ret) 1971-75; 1979-95 (20 yrs)
2003 U320 F03 [6179] 38PBDS (3/2016)
2016 Chev Silverado Z71 LTZ
Motorcade 17738
--------------------------------------
New Horizons 5W 25' RKS (1/2004 - 3/2016)
2003 Chev Silverado 2500HD Duramax
Tent (5-person) White Stag (1972 - 2003)