Aqua hot won’t fire up

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Aqua hot won’t fire up

April 03, 2021, 01:40:59 pm

Doing my monthly testing of systems and when turning on the Aqua hot the blower fan starts and runs for 2 1/2 minutes then the fan shuts off. I tried this 3 times with the same results. The unit has worked fine since I last worked on it with Rudy's help.
I'll get out the manual and search for the problem now but hoping to get a faster answer with the help of the members here.
Thanks in advance.

Re: Aqua hot won’t fire up

Reply #1 – April 03, 2021, 02:10:35 pm

Does the light on the toggle switch stay on?

I'm having a similar issue and my light goes out. I cleaned the flame sensor and serviced it including a new nozzle. I thought it was fixed but it seems to be an intermittent issue. Mine does fire up and purr with no smoke. Yesterday when it turned off after about 5 minutes, the light also went out, I flipped the electric toggle on, the light came on and then diesel light came back on simultaneously and fired back up.

Re: Aqua hot won’t fire up

Reply #2 – April 03, 2021, 03:18:34 pm

With the motor running and failing to fire, check high limit thermostat is closed and check the coil to see if it is arcing the ignitor points.

If you have a black plastic Sperior control unit, that is suspect too.

Re: Aqua hot won’t fire up

Reply #3 – April 03, 2021, 04:09:25 pm

J R, yes my light stays on when the motor is running, (2 1/2 - 3 min.) then goes out when motor shuts off.
Rudy, testing VDC high limit Tstat with wires connected = 00.0, with wires off= 00.0 and a signal tone.
Testing VDC controller Tstat with wires connected = 00.9, with wires off= 00.2 and a signal tone also. Meter is set for continuity.
I have a new controller that I got from you last September and all has been fine until today.
Will check the other steps you outlined above and report back. Thanks!

Re: Aqua hot won’t fire up

Reply #4 – April 03, 2021, 07:32:26 pm

Removed burner head and after turning it 90 deg noticed that one of the ignition coil wires had come off and was not making contact with the ignition probe. Re attached the wire and put everything back together and started the unit again. Alas, no joy!
Tomorrow I'll start again where I left off on the troubleshooting steps and see what I come up with.😡. After seeing that wire disconnected, I thought for sure that was the problem, silly me.

Re: Aqua hot won’t fire up

Reply #5 – April 04, 2021, 12:04:04 am

I had intermittent problems that turned out to be a bad insulator on the electrodes. I could hear it sparking, but it was not always sparking between the electrodes. sometimes it was shorting through the insulator

Re: Aqua hot won’t fire up

Reply #6 – April 04, 2021, 12:43:14 am

Steve, I'll check that out tomorrow when I start back on the troubleshooting process. I really thought the loose coil wire was the problem.

Re: Aqua hot won’t fire up

Reply #7 – April 04, 2021, 12:50:42 am

Quote from: rbark – April 04, 2021, 12:43:14 am

Steve, I'll check that out tomorrow when I start back on the troubleshooting process. I really thought the loose coil wire was the problem.

Be sure to check the gap also. Can you hear the crackling as the coil fire the electrodes?

Re: Aqua hot won’t fire up

Reply #8 – April 04, 2021, 10:12:43 am

I had a intermittent coil.

Re: Aqua hot won’t fire up

Reply #9 – April 04, 2021, 03:19:14 pm

Up date, coil is fine, good spark when testing from 12VDC. I need to buy a GOOD multimeter to test the photocell. Troubleshooting guide says to cover photocell and you should see 3000,000 ohms, uncover and should be 300 ohms. My meter isn't anywhere close to that! Just for good measure I installed a new one anyway and all things lead me to the control box which is just 6 months old which bothers me.
Taking the rest of the day because it's Easter Sunday! I hope everyone enjoys this day.

Re: Aqua hot won’t fire up

Reply #10 – April 04, 2021, 03:28:08 pm

Quote from: rbark – April 04, 2021, 03:19:14 pm

all things lead me to the control box which is just 6 months old which bothers me.
Taking the rest of the day because it's Easter Sunday! I hope everyone enjoys this day.

These control boxes seem to be the Wolf's Bane of the Aqua hot system. Bought our coach in 2015 and we are on our third control box and a total rebuild. And thus we are into our AH to the tune of $13K (the single largest expense of any system on our coach)
I wonder if the heat where these boxes reside might be part of the issue. Perhaps extending the leads and removing that control box from the hot confines of the Aqua Hot box itself might be something to try.

Re: Aqua hot won’t fire up

Reply #11 – April 04, 2021, 03:42:52 pm

Could the vibrations from the Webasto + the heat be causing failures?
I like the idea of extending the wires and moving the control box. I'll be servicing my aquahot in the next week or so and I'll look to see if it's possible to just mount the box without changing the wires.

Re: Aqua hot won’t fire up

Reply #12 – April 04, 2021, 04:01:41 pm

Quote from: folivier – April 04, 2021, 03:42:52 pm

Could the vibrations from the Webasto + the heat be causing failures?
I like the idea of extending the wires and moving the control box. I'll be servicing my aquahot in the next week or so and I'll look to see if it's possible to just mount the box without changing the wires.

That was actually done to a very small degree with the new (and Improved?) in house control box. It has a pigtail. Seems like an easy DIY, provided the connectors are standard or if AH Hq would sell that connector to an end user.

Re: Aqua hot won’t fire up

Reply #13 – April 04, 2021, 04:49:29 pm

I did do that when I got the new and improved unit. I'm still going to wait until I get a better VOM and retest the components to make sure I didn't miss anything before I get another control box. I will probably order the 2 DC Tstats also.

Re: Aqua hot won’t fire up

Reply #14 – April 05, 2021, 06:49:32 pm

Ok, I need help with this! Going by the troubleshooting guide, I'm checking the diesel-burner's VDC high-limit Tstat for continuity. With wires connected I get a reading of 00.4, with the wires off I get the same reading. Checking the diesel burner's VDC control Tstat with wires connected I get a reading of 3.4, with wires off I get the same reading of 3.4. I don't want to make an ass out of myself but I'm assuming that the controller Tstat is the bad one. I can't really go to the next step until I know if these Tstats are good, or one is bad. Any help will be much appreciated! Thanks.

Re: Aqua hot won’t fire up

Reply #15 – April 05, 2021, 07:12:52 pm

Richard, give Rudy a call and see what he says! He won't steer you wrong.

Re: Aqua hot won’t fire up

Reply #16 – April 06, 2021, 05:54:04 pm

Ok, here's my update. Called Rudy this morning and he walked me through the troubleshooting guide until everything pointed to the control box. My Tstats were good, coil was good, igniter was good, return fuel was good and DCVs were good but just would not fire up the burner. I thanked him for all his help and put a call into the Aquahot dealer and got on the call back list. While waiting for them to call me I decided to look at my old control box (the silver waves to one). Opened it up and found absolutely nothing wrong with it as far as the eye and magnifying glass could tell, so I buttoned it back up and installed it, turned the switch on and the purge cycle started and by the time I got over to the AH compartment the burner came on and ran for a full cycle!
I then shut the unit off and installed the new black controller that has the pigtails that I got from Rudy this past December.
Turned switch back on and low and behold, the unit went through the purge cycle then the burner came on, as it should and ran for a full cycle also until it also shut off and went through the cool down cycle.
The moral of the story is, I'm happy that the Aquahot works, but unhappy that I couldn't find out why it did not work for the last few days! I hate Gremblins!!!

Re: Aqua hot won’t fire up

Reply #17 – April 06, 2021, 06:15:11 pm

I hate hearing that the new and improved control box doesn't seem to last longer than the previous version

Re: Aqua hot won’t fire up

Reply #18 – April 06, 2021, 06:45:30 pm

Well, it worked after all on both his old silver box and new Aqua Hot box. Not being there so can not help with what the glotch was but it is working now.

Re: Aqua hot won’t fire up

Reply #19 – April 06, 2021, 07:40:16 pm

Maybe use some (a very small amount) of the electrically conductive grease on the contacts.

Re: Aqua hot won’t fire up

Reply #20 – April 06, 2021, 08:00:06 pm

I'm hoping the new controller is fine and just a glitch in the system. When the troubleshooting steps take you to it being a faulty control box, that should be it.
Roger, didn't think about the electrical grease at all, thanks for that idea. Will do that tomorrow.
At any rate, it's working now and I have a " used but good " spare in case I need it.

Re: Aqua hot won’t fire up

Reply #21 – April 07, 2021, 08:48:30 am

Aqua Hot......We have a love hate relationship with them.

Re: Aqua hot won’t fire up

Reply #22 – April 07, 2021, 09:25:21 pm

Lets think about this.
Unit did not work,
removed new box
installed old box.
Unit works.
Uninstall old box
Install new box.
Unit works.

So what is common denominator?

You disconnected the wires to the control units.

You had a bad connection on one (or more) of the wires when you disconnected the new one. I bet if you had just unplugged the new controller and plugged back in it would have worked.

Now do as Roger said, to the connections.

Gremlin moved on to something else or your neighbors coach.

Re: Aqua hot won’t fire up

Reply #23 – April 07, 2021, 10:23:23 pm

Nope, still here! I thought the same thing so I tried the unit today. Purge and no start with the new unit. Unplugged and applied some electric grease on terminals and plugged back in. Also inspected wire connectors on the harness.same thing, purges but won't fire. Swapped controller with the old Webasto and functioned as it should. Purge, ignite, burn, purge and the shut down.
I am missing something but can't figure it out yet. Talked to AH tech today and told me to ohm the photo-cell covered up with rag and uncovered, even though it's a new one, 300,000 ohms covered and 300 ohms uncovered, check fuel return flow with same size hose (I used a larger hose) and check fuel PSI which should be 145. One thing I noticed when running the unit was the 12VDC at the + & - posts for the AH was 12.67 with unit off and 11.37 with unit on. Have no idea if that is normal or not. Do I possibly have a low voltage issue?
The tech did say to send him the new controller if it didn't work today and they would test it and let me know if it's good or not.
More to come tomorrow.

Re: Aqua hot won’t fire up

Reply #24 – April 13, 2021, 01:37:43 pm

I haven't confirmed that voltage at the posts recently, but when Rudy worked on mine in NAC a few years ago, his test box, which was plugged into the controller harnesses (controller bypassed) was reading voltage in the 11V range while running also. I was a little surprised as my house batteries are lithium and are normally above 13V.

I don't remember what size the wires are at the post, but I believe you're getting voltage drop as I did, due to the small wire size under load. I wonder if this its what's contributing to controller failures along with heat, it sure doesn't help.

Rudy replaced the motor bearings and controller on my coach, and did a fine job. He even let me turn a few wrenches while teaching me how the unit works.

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