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Topic: 2003 U320 - DIY Rebuilding of Aquahot Control Box (Read 1953 times) previous topic - next topic

2003 U320 - DIY Rebuilding of Aquahot Control Box

During the last year, our Aquahot diesel blower has started turning off and on during cool down after the burner turns off.  The frequency of the off-on cycles has increased over time.  Not knowing for sure what was inside the Webasto control box, I assumed the problem was a relay going bad (weak spring, contact pitting, whatever).

A search of Foreforums reveals posts by David Bethard and Chris Lang Webasto SG 1553/12v controller Aqua hot 431.  David suggested that the problem lies with the electrolytic capacitors.  He goes on to list the 6 electrolytics on the control board.  Encouraged by this post I decided to replace the caps on my board.  I have a bunch of electronic stuff that included most of the caps.

Removing the circuit board from the silver can is a bit destructive (at least for me).  I broke off a small portion of the plastic end cap so I could get a screwdriver under the lip of the can.  A little cutting of the sealing material and a gentle pry, and off it came.  See attached photo 1.

The board has 5 big relays in addition to the 6 electrolytic caps.  The relays are not sealed, so it is very easy to inspect the contacts and to measure the spring strength.  All were found to be in excellent condition.  As for the caps, there were no outward signs of issues.  Sometimes bad electrolytics are swollen or have liquid leaking out.  I could see none of this (the globs of stuff on each of the caps is glue that holds them in place).  So I just replaced all but C4.  I didn't have one.  See attached photo 2.

Replacing them was easy.  The board is an old analog board with lots of space between components.  Plenty of room for soldering iron and solder sucker.

I put some tape around the joint between the endcap and aluminum can, reinstalled it, and all is now fine. 

An alternative solution is to buy a new control box.  The new ones are make in Ukraine by Spheros.  You can buy them for $325 from http://www.heatso.com/spheros-control-unit-sg-1553-12v/.  Chris bought one. 



Jim McNeece
2003 U320 40'
2017 Chevy Colorado Tow

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #1 –
Another solution is to have yours rebuilt by Jim Frerichs listed on the commercial listings. He did one of mine and it is still going strong. I bought one of the plastic ones from a forum member who had sold the coach and I carry it and a brand new metal one as spares.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #2 –
Interesting, If I understand correctly what you are discribing it may be what I am currently experiencing. When I have my diesel burner switch on Aqua Hot functions perfectly and continues to supply great heat  but once burner warm air brings coach up to temperature I am hearing the unit actually fluctuate up and down like 3 to 8 times before it shuts it's self down. Does this sound like what your issue was? I thought maybe it was just burning off remaining fuel before shutting down. I just had complete service of Aqua Hot system done in September at MOT...?
Chuck Wiggy
Coloma, Wisconsin
Sold my 1999 U 320 40 Ft. M11 450 hp
Build # 5468
2009 Silverado

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #3 –
Quote from: muskyman475 –
Interesting, If I understand correctly what you are discribing it may be what I am currently experiencing. When I have my diesel burner switch on Aqua Hot functions perfectly and continues to supply great heat  but once burner warm air brings coach up to temperature I am hearing the unit actually fluctuate up and down like 3 to 8 times before it shuts it's self down. Does this sound like what your issue was? I thought maybe it was just burning off remaining fuel before shutting down. I just had complete service of Aqua Hot system done in September at MOT...?
You are experiencing a controller starting to fail. It will eventually just keep cycling. You can manually turn it off and back on for a while and it won't keep cycling until the next heat and cool down. Servicing wouldn't have discovered this.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #4 –
Chuck, your Control unit is indeed failing.  Your choice is a reman box from JIM Frerichs or a new solid state, no moving parts, Control Unit designed and manufactured by Aqua Hot for only $893.

Do not consider a black Sperios one as Aqua Hot had so much grief from them they designed their own.  Some are good, lots failed sooner than later.

If you want the AH control unit, contact me and I will offer you a discount
Rudy Legett
2003 U320 4010 ISM 450 hp
2001 U320 4220 ISM 450 hp
1995 U320 M11 400 hp
1990 Granvilla 300 hp 3208T
Aqua Hot Service Houston and Southeast Texas

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #5 –
I wonder if the reason the Spheros control boxes didn't work for Aquahot is the fact that Aquahot placed the control box inside the cabinet.  This could have resulted in the Spheros not getting enough ventilation, thereby, overheating.  So you maybe could use a Spheros box if you mounted it outside the Aquahot cabinet. 
Jim McNeece
2003 U320 40'
2017 Chevy Colorado Tow

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #6 –
Having the Speros box outside of the heater would not explaing the two Speros boxes that I took out, installed and would not start the burner from the get go.  Aqua Hot warranted both of those brand new control units which added to their desire to have a reliable control unit that works mounted to the burner as is designed by Webasto, the burner manufacturer.

But, some of the Sperios boxes give no trouble.  No silver boxes failed from the get go or failed in 9 to 14 months like 4 black boxes I have replaced beyond the 6 months warranty.  No Aqua Hot control units have failed so far, especially from the get go.

Please use the unit that suits you best.  But neither I nor Aqua Hot will sell you a Sperios box.
Rudy Legett
2003 U320 4010 ISM 450 hp
2001 U320 4220 ISM 450 hp
1995 U320 M11 400 hp
1990 Granvilla 300 hp 3208T
Aqua Hot Service Houston and Southeast Texas

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #7 –
I got a PM from Chris Lang who I mentioned in my initial post as a person who had purchased one of the Ukraine boxes.  He said his failed just after the warranty expired.  This agrees with Rudy's experience.  So, the new style box is not a solution. :( 

If you are not inclined to take on this task yourself, contact Jim for a rebuilt original.  These are analog boards with simple electronics - a few transistors, a bunch of diodes and resistors, 6 electrolytic capacitors, and 5 heavy duty relays.  A rebuilt one should be just as good (if not better) than the original.  Jim's price is not unreasonable.  Not much more than 2 or 3 hours of shop time at most RV repair places.

It sure would be nice to know the part number for the two types of relays on the board. ;)

Thanks, Rudy, for your input.
Jim McNeece
2003 U320 40'
2017 Chevy Colorado Tow

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #8 –
Rudy I am going to personal message u for I am worried how long my system will keep functioning. Thank you ALL!
Chuck Wiggy
Coloma, Wisconsin
Sold my 1999 U 320 40 Ft. M11 450 hp
Build # 5468
2009 Silverado

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #9 –
Rudy is d-man when it comes to aqua hot!!!
The selected media item is not currently available.Keith & Jo
2003 U320T 4025 PBBS Designer series
Build 6203    Cummins 500hp
2000 U320 4010 WTFE / Build 5762 —Sold—
Motorcade #18070   
Pasadena, Texas
2015 Jeep Wrangler Sahara-Sunset Orange pearl coat
Don't argue with a fool, people watching might not be able to tell the difference.

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #10 –
I bought a solid state box from Rudy last April. No problems so far. Had my old silver box rebuilt by Jim as a spare. Went through two boxes in three years. I like the idea of solid state, a lot. Rudy is the MAN.
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT
 

Re: 2003 U320 - DIY Rebuilding of Aquahot Control Box

Reply #11 –
Well , as Keith had earlier stated..." Rudy is da man".  Rudy and I had a great conversation.  Rudy has arranged to have the solid state control box overnighted from Texas to Central Wisconsin. It arrives this afternoon and just as the temperature is going to dip to zero. Rudy thank you again... The man is a walking book of knowledge not only did he assist with the part but took time to answer some questions and share some very beneficial information. As someone who is brand new to the full time coach living and not very knowledgeable of how everything functions, the little tricks, specialty items etc. I would just like to take a minute and express my appreciation and respect for all of you who take time out of your days or nights to put forth the effort and assist those of us who are just learning or maybe just at that point where frustration has clouded clear thought.  You ALL Truly make this adventure a bit easier when a person has such a great resource to turn to knowing that the seasoned well experienced individuals are willing to share such great information without making you feel like a moron when asking maybe some of the simplest or most obvious questions. I tip my hat to all and wish everyone SAFE travels and may your Holidays be full of happiness!!! Thank you.
Chuck Wiggy
Coloma, Wisconsin
Sold my 1999 U 320 40 Ft. M11 450 hp
Build # 5468
2009 Silverado