I am looking into replacing the 22 year old Thomas TA-4101-DC auxiliary air compressor. It is a 1/3 HP 28 amp motor.
I know I could rebuild it but I'm not going to for various reasons. That's for another thread.
What I would like to know is what is the actual wire gauge going to the solenoid and motor ?
I've scoured all the forums, wiring diagrams, and online info. This is the closest info I found: is:
Wire size to be minimum 8 gauge.
I am considering a motor with a 50 amp peak load. Would like to know that is is 6 gauge. Anything less would give me some concern, or more work.
Thanks all
2002 U320
Think you're going in a good direction. Some of the insulations can outright stink. I recently gots some #4 gauge wire and it still stinks. I would not want it inside anything especially my coach
We have the Thomas TA compressor info in the Media section

We also have that and more in the Wiki HWH Aux Compressor (https://wiki.foreforums.com/doku.php?id=technical:hwh:aux_compressor)
If you look for the wire number(s) for the power to your compressor in the coach schematics or owner's manual, it should indicate the existing wire gauge.
B-2126 for a 2003 U320 shows wires C18 as 8 gauge red, and C19 and 8 gauge green for the aux compressor power/ground. Fed from a 40 amp resettable 12VDC breaker. I don't recall the amperage of the inline fuse that's used for slide bladder operation, but I'll poke around in the morning.
Yup, it's 8 gauge, but it only has to go from the circuit breaker to the pump, which is about 10' in my '03. I did a thread about replacing this pump with a much less expensive Air Zenith that moves about 3x the air (works less and is faster), and is completely rebuildable.
Keith's topics:
Aux air pump system replacement (https://www.foreforums.com/index.php?topic=44535.0)
Replacing the aux compressor and HWH pressure requirements (https://www.foreforums.com/index.php?topic=44265.0)
Noting that AdventureSofie has a 2002, there's the possibility it has the one-year-only air-operated awning, which might also be contributing to the desire for a beefier aux compressor. There have been some issues reported in the past that the TA-4101 isn't up to maintaining the pressure needed for that awning (and many have replaced the awning with a manual Zip Dee model).
I forgot about the Wiki. I didn't realize that was what the wire diagram was showing. I knew it had a 40 amp breaker which is also agrees with the 8 gauge wire.
I read that thread. It's rated at 35 amps so that would be a drop in. I assume you are still happy the performance and sound.
Also, my coach does have the non-operative air-operated awning. Since the Thomas compressor only gets to 65 psi, I'm not sure it is broken. I see some efforts on repairs from the prev owner.
Keith (and I'm sure many others) outlined all the tribulations I'm going through now. I'm not sure that much has changed in what is available in the compressor market since then. I'll start a new thread on my compressor replacement quest once I get my plan together.
Andy, I have the Air Zeneth that Keith talks about. On my 2002 it will supply 110 lbs or more. I recall Jimmy from ZipDee stated for the ZipDee awning 100 lbs is required. Air Zeneth has excellent customer service with 2 day replacement parts across the US. Jim.
Also Keith Risch said he is seeing more and more of the Air Zeneth compressors come through his shop now. He wanted the contact info from us when we were there. Jim.
It was. I used the factory wiring from the circuit breaker to the additional breaker (that I didn't need) at the pump module. Drop in, doesn't pop the breaker and is just barely louder than the Thomas with the muffler installed. It's made over 150psi in this config (when testing the pop-off safety valve) and is rated for 100% duty cycle.
Was Keith's observation that there was issues or that they were just more common now?
I was hoping for something as quiet or quieter than the Thomas. The Thomas specs claims 70 dB and 100% duty cycle. I'm guessing you measured your worn out rattle trap. Mine is really loud right now. Very curious what a new Thomas sounds like.
Your first measurement of the Air Zenith was 87db which is quite loud. It is spec'ed at 75 dB, but that is probably out in free air, not installed in a bay. I did see your write up of the Air Zenith sound measurement after the muffler install. You gained 2-5 dB which isn't too bad. Still higher that I was hoping for but there is no denying the performance. Maybe some better structural isolation would knock it down more. Thanks for you input.
It would be "kinda pricey", but you might entertain lining the bay ceiling and maybe the walls with Dynamat.
Boat & Marine Sound and Vibration Control | Dynamat (https://www.dynamat.com/applications-industries/marine-rv/)
Heat Protection and Thermal Insulation For Your Car | Dynaliner | Dynamat (https://www.dynamat.com/products/dynaliner/)
I recall that WS6_Kieth or someone used the Dynamat type of sound damping with limited success for in the Coach, but did improve the exterior sound level. Every little bit helps. I had thought of making an enclosure over the pump but it would need additional airflow.
I read of various way to reduce the vibration noise transmitted through the mounts. They were using closed cell foam under the pump, using new rubber isolation mounts, or use Sorbothane isolators. Sounds like a good science project for someone.
Now back on topic. I just need to decide speed vs. sound level since I'm just doing a pump replacement and not the awesome control system that WS6_Kieth did.
Yeah, there's a lot involved in the isolation mounts - durometer, noise frequency and amplitude. We had experimented with a few options many years ago. Some actually made it worse.
I did a bit of research on available pumps before choosing the AZ. Cost was one factor, as was noise and volume. The AZ was about 1/4 the cost of a replacement Thomas and offers roughly 3x the volume, and the noise increase was only a few db. The AZ rebuild cost is also much cheaper, and individual parts like pistons, rings, cylinders, reeds, etc, are available.
While I revamped the whole system, that is not required. Fourdayoff (Jim) just replaced his pump with the AZ and kept all the original controls and has had good luck with that setup.
Andy, Keith did not mention any issues with the A/Z only he is now seeing more and more replacing the Thomas. I'm happy with mine as far as noise goes. I did retrofit my original remote muffler and that did reduce allot of noise. New isolator mounts also. Allot quieter than my worn out banging Thomas of 21 years. Cost was a nice factor. Jim.
Jim,
Did you replace anything else for the pump like lines, relay, valves, wires, etc?
Andy, I did use the relay and harness that comes with the A/Z. I had some braided steel line with a/n fittings in my shop to use for the outlet port to the filter bowls. I removed the muffler from the A/Z added it to the end of my original compressor muffler. fabricated another steel braided line to mount the muffler on the wall next to the compressor. I'm showing 56 db inside the coach in the kitchen, 65 db outside next to the closed basement door and 76 db right next to the compressor. It would be nice if it was quieter in the kitchen but tolerable. Jim.
Andy, I didn't need to use the a/n fittings and lines it was stuff I had on hand. I'm sure any good air line would be fine. Jim.
Thanks Jim. I used the "Sound Meter" app on my Samsung Android phone. It showed over 90 dB in the bay and in the 70s outside with the door closed. My pump assembly is mounted on a platform up in the bay.
I was earlier leaning toward the Outback Extreme High Output as I thought it would be even more durable and I was hoping quieter than the AZ. prfleming sent me some sound measurements that are not as good as I had hoped.
1 ft 82 db
3 ft 78 db
Regardless, can't wait to get this changed out.
Andy, yours looks like it's mounted in the same position as mine so here's a pic of mine completed also remember that installing the factory muffler does make a difference in the sound output thanks,

Jim.
Jim,
Does your setup air up the entire coach? When I converted the 115V compressor to 12V in my '91, that was connected to the main air tanks.
Peter, yes it does air the brake tanks also so that you can sneak out of the park quickly. Jim.
Jim. Looks very similar but mine is mounted up a little higher so I don't have extra space above. Are the brass fittings, unions, shutoff, etc 1/4" AN ? and where did you source them from?
Andy, the platform on mine is 9 7/8" from the ceiling. Room for the A/Z with about 1" to spare. The fittings can be sourced from a hardware store. No valves, unions needed. Once you see the A/Z you'll get it, I kept it simple. Jim.
Fittings are 1/4" . You can get them from Amazon a lot cheaper then the hardware stores, plus you will not have to go to them and find out they don't have the parts you need.
I was looking for the fuse for the pump. It should be a 40 amp fuse per the wire diagram. Oddly it is labeled as a 15 amp in the coach. I think it is mislabeled since it has run all these years. Is there a way to see what size the fuse is without removing it?
Use a mirror and see if you can see the sides of the relay. There should be print on the side of it.
(https://m.media-amazon.com/images/I/612q-M4Ff1L._SL1500_.jpg)
Mine is 40 amps. Maybe a larger pump?
Yes, this must be an older label. The 1/3 HP Thomas pump came with this coach and is listed as 28 amps max load. I don't recall what year Foretravel changed to the bigger pump so the factory used the wrong label here.
I'll need to get my borescope out to see around the wiring to find the writing on the side of the fuse.
I looked up the GLOSO product on line.
Ok, this is an auto-resetting circuit breaker rather than a fuse. That's nice to know. Available on Amazon too.
Does it give you an amperage value?
That's a picture of the circuit breaker I used when I replaced the failed A/C condenser circuit breaker, but it's the same form factor size. The ones in the main circuit breaker panel are not auto-resetting units.
I guess I should just take a little more effort to look for the markings. I just assumed it was on the back. It was on the lower side of the breaker. I rotated the photo so I could read it better. It was a 40 A breaker.
The ones in my coach are the Eaton Bussmann Series Short Stop model. It looks like it is a Type III manual reset breaker. The breaker has to be manually reset with the push of that black button on the end. Thought I'd share that as I didn't know how they were reset.
Also, I read that a 24V breaker is more robust and works just fine in a 12V system.
Jim, the AZ info shows a 70 Amp fuse for power. That seems excessive. Did you change out your 40 amp fuse?
Thanks
Andy, I did not replace the 40amp. Sorry for the slow response. On the road. Jim.