1994 U300 Electric Coolant Circulation Pump Failure

Topic: 1994 U300 Electric Coolant Circulation Pump Failure (Read 844 times) previous topic - next topic

1994 U300 Electric Coolant Circulation Pump Failure

January 31, 2020, 11:10:50 pm

Sunday I have a electrical safety issue on my 1990 U300. I was checking out the systems and turned on the aux pump to help circulate the anti freeze before starting the 6V92. No noise so I went back to check it. Sparkling and smoke coming from the pump motor. Quickly turned it off. No good, keep sparking and really smoking. Got my knife and cut the wires. After removal of the wires, it wound up at a Bosch relay. Melting the connection. The relay welded close! Tracked the supply side to a large contractor. Direct with OUT any fuse or breaker! The pump motor was seized and the brush melted its holder. The relay was on the battery isolator panel. If I had been driving it at the time, it probably would have caught fire before I realized what was going on. The drawings showed the dash switch, but not the pump. I have most of the prints and manuals due to the last owner! Thanks 🙏

Re: Electrical safety issue on 1994 U300

Reply #1 – January 31, 2020, 11:23:47 pm

The aux coolant pump must be unique to the U300 with 6V92. We do not have the pump on our '93 Cummins U280 with C8.3.

My B-2126 Automotive Wiring Diagram does show where the pump relay would be positioned on the U300 isolator panel. On my isolator board, that relay is not present. Power for the relay comes off the AUX START SOL. There is no circuit breaker shown on the power feed.

Good work with the emergency shut down and diagnosis of failed components!

Re: Electrical safety issue on 1994 U300

Reply #2 – February 01, 2020, 01:47:05 am

It was a perk added to bring more heat to the front in cold weather. Good to put a breaker in the circuit. Strange they did not.

Pierce

Re: Electrical safety issue on 1994 U300

Reply #3 – February 01, 2020, 05:20:20 am

Quote from: Pierce & Gaylie Stewart – February 01, 2020, 01:47:05 am

It was a perk added to bring more heat to the front in cold weather. Good to put a breaker in the circuit. Strange they did not.

Pierce

Was this circulation pump a factory option on the 6V92 or would my 1994 have one? Where would the switch be?

Re: Electrical safety issue on 1994 U300

Reply #4 – February 01, 2020, 06:16:22 am

My coach has a switch on the dash for this but I've never used it.

Re: Electrical safety issue on 1994 U300

Reply #5 – February 01, 2020, 08:29:04 am

Perhaps the OP (mraycal) will tell us where the failed pump is physically located on his coach, or better yet provide some photos?

Or some other owner (Pierce or kenhat)) can tell us the location. Something that should be checked as part of normal maintenance routine?

Re: Electrical safety issue on 1994 U300

Reply #6 – February 01, 2020, 08:39:44 am

Never mind. I did what I'm always encouraging other members to do: SEARCH THE FORUM ARCHIVES!

Found a reference and photo:

Aux pump name or part #

Re: Electrical safety issue on 1994 U300

Reply #7 – February 01, 2020, 08:59:50 am

I even participated in a discussion about this exact component...and totally forgot it. Senility is sad in one so "young" as myself.

What does this [device under engine] do?

Re: Electrical safety issue on 1994 U300

Reply #8 – February 01, 2020, 09:25:48 am

I see the links to a replacement pump part number (in the old post above) are dead. There is mention of a "GROCO pump" so I googled that term. Found the one below as a possible replacement?

Automotive Continuous Duty Centrifugal Pump|GROCO

Re: Electrical safety issue on 1994 U300

Reply #9 – February 01, 2020, 09:29:59 am

I do have B-2126 and the water pump on the print is the coach fresh water pump, not the auxiliary. Follow the drawing reference B2035,B2037,B2156. It shows the latching relay and multiple switches. Yes the auxiliary pump was factory installed and in the factory harness. The harness hadn't been touched by any one till me. The protective sleeves were all in tact. The panel was not altered. This is similar to what I do for a living. I will post pictures, but I just replaced the pump last night and have the bad wire removed. I will post the locations and damage. The new wiring should be finished today with proper fuses and relays. I removed 12 feet of the wire in the harness as it went around the motor. That's a lot of work, but I had to inspect the harness along the way to ensure that there was no other damage.

Re: Electrical safety issue on 1994 U300

Reply #10 – February 01, 2020, 09:36:30 am

I did replace my pump and it works as it should, it really helps adding more heat up front on cold mornings. If I remember they are used on school buses that have hydronic heating to move the heated liquid through the system.

Re: Electrical safety issue on 1994 U300

Reply #11 – February 01, 2020, 11:00:59 am

Notice B55 RD wire has no protection! Here is my schematic. Thanks for your post, it helps me to verify it.

Re: Electrical safety issue on 1994 U300

Reply #12 – February 01, 2020, 11:40:03 am

Quote from: mraycal – February 01, 2020, 11:00:59 am

Notice B55 RD wire has no protection! Here is my schematic. Thanks for your post, it helps me to verify it.

Yer welcome.

Added another photo to my post above - shows the build numbers covered by my B-2126 schematic.

Notice the hand-written notation on my drawing saying it is applicable up through build #4389.

What is your coach's build number?

Re: Electrical safety issue on 1994 U300

Reply #13 – February 02, 2020, 05:29:18 am

Could one of the moderators "add" - "water circulation pump" to the heading on this post? Or adjust the title to reflect the area of concern.

Electrical safety issues continue

Reply #14 – February 02, 2020, 09:06:52 am

The photo I was posting error

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #15 – February 02, 2020, 09:08:44 am

Quote from: Gerry Vicha – February 02, 2020, 05:29:18 am

Could one of the moderators "add" - "water circulation pump" to the heading on this post? Or adjust the title to reflect the area of concern.

Done and merged to original thread the post with pictures immediately above.
Brett

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #16 – February 02, 2020, 09:20:12 am

Great photos of the "before" damage. How about some photos and source/part number info on your replacement pump?

I really like the "relay block" addition - haven't seen one of those before. Much cleaner than the factory relay placement!

What is the build number on your coach?

Re: Electrical safety issue on 1994 U300

Reply #17 – February 02, 2020, 09:36:33 am

Quote from: Gerry Vicha – February 01, 2020, 05:20:20 am

Was this circulation pump a factory option on the 6V92 or would my 1994 have one? Where would the switch be?

Gerry,

What was the answer to your question? Does your coach have this pump?

The pump switch (AUX PUMP) should be with the other rocker switches over on the left dash panel, below the headlight switch.

If you do have the pump, I guess it would be prudent to add a correctly rated circuit breaker to the relay power wire.

Bussmann Automotive Circuit Breaker, CBC-B, 20A, 14V CBC-20B | Zoro.com

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #18 – February 02, 2020, 10:39:45 am

Johnson Pump 3/4 in. CM30P7-1 Centrifugal Pump 10-24504-03. Rated for water and anti freeze. $125
EDGE INDUSTRIAL 1" X 3/4" Hose ID Brass Barb Reducer SPLICER Fitting Fuel / AIR / Water / Oil / Gas / WOG, section of 3/4 heater hose.$10 each
MICTUNING 12-Slot Relay Box,6 Relays,6 ATC ATO Fuses Holder Block with 41pcs Metallic Pins for Automotive and Marine Engine Bay $14.
All from Amazon.
Miscellaneous items terminals, 2 splices, wire black wire plastic cover, fuse and Bosch relays.
Photo for more new should be posted today. It got late last night and I was very tired climbing all around and under the engine. It's at my hanger and I don't have WiFi there. It's a great place to work on it inside.

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #19 – February 02, 2020, 10:50:53 am

For those with the "electrical panel" behind the driver's rear tire, I STRONGLY suggest relocating it to a less harsh environment.

In many cases it can be relocated to the electrical area at the foot of the bed with no changes in wires or connectors. Been there, done that.

Certainly, a move to the from panel of the engine room would be another much dryer option.

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #20 – February 02, 2020, 10:57:35 am

I don't run unfused wires into the compartment or very far from the contactors that they come from. It's a safety issue

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #21 – February 02, 2020, 11:04:06 am

The wire is PVC wire stands for poly vinyl chloride. When it burns it puts off toxic chlorine gas not good for inside. Yes I know the coach is wired with that but I try to limit what wires are in there. And if I change your location that drastic the next owner will have a very hard time figure it out just what has been done. I was trying to keep it as close to the OEM as I can while maintaining it Safety.

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #22 – February 02, 2020, 11:04:28 am

Couple of points:

First "distance from contactors" is exactly the same.

Most electrical failures are due to corrosion, resistance, loose connections. These are materially lessened if they are located in protected areas.

And certainly nothing wrong with fusing leads-- equally good safety measure irrespective of location.

Connections on the board can be exactly the same in the new location. Wires/plugs are carefully labeled, disconnected, board cleaned and any "marginal" components replaced with new ones and remounted on the board. Board moved to new location and original connections plugged back in. Only change would be if fuses/breakers are added.

I have just inspected too many coaches where those electrical components were severely compromised-- particularly true of any coach driven on salted roads or parked near salt water.

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #23 – February 02, 2020, 11:19:42 am

Quote from: wolfe10 – February 02, 2020, 10:50:53 am

For those with the "electrical panel" behind the driver's rear tire, I STRONGLY suggest relocating it to a less harsh environment.
In many cases it can be relocated to the electrical area at the foot of the bed with no changes in wires or connectors. Been there, done that.
Certainly, a move to the from panel of the engine room would be another much dryer option.

Yes, yes, yes. Brett is spot on! What was Foretravel thinking when they put the behind the driver's rear tire? I've seen some that were barely recognizable as electrical panels. If the panel is put in the space at the foot of the bed, an extra hour or so to line the compartment with backerboard would be a good idea.

Pierce

Re: 1994 U300 Electric Coolant Circulation Pump Failure

Reply #24 – February 02, 2020, 06:51:42 pm

Quote from: Chuck & Jeannie – February 02, 2020, 09:36:33 am

Gerry,

If you do have the pump, I guess it would be prudent to add a correctly rated auto-reset circuit breaker to the relay power wire.

Bussmann Automotive Circuit Breaker, CBC-B, 20A, 14V CBC-20B | Zoro.com

Ixnay on the reakerbay. The FAA issued a notice to not reset tripped breakers in flight because once is enough and enough resets may trigger a fire. Having an auto-resetting breaker is only delaying the inevitable, sort of a slow motion overload. Better to have a manually reset circuit breaker or fuse.

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