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12V Webasto Heat problem
Hi All,
I’m not getting coach heat from the 12V setup. Here’s the situation:
The first time I tried the Webasto it sorta seemed like it wasnt firing correctly and it blew a lot of white smoke and semeed to only fire for a few seconds then stop. I took it apart after reading around about it – and although I didn’t replace parts, I took a can of brake cleaner and cleaned everything really well. The photo cell came out looking new!
Now – the websasto seems to run as my noobie self would think it should. It runs for quite a while when you first start it up and it will then run in little spurts thereafter. No smoke at all. Makes the whining sound like a mini jet engine.
While it’s running, I’ve followed all the hoses I could find and the coolant IS getting hot and circulating around the middle bays. In the Curbside water bay there are 4 coolant hoses on the ceiling and all of them are warm to hot. The valves are all open too. There is 1 meanual valve in the webasto bay which is open also. There is an electro-valve in there that I don’t know if it’s stuck or not. It heads back to the engine as though it’s for block heat.
The bus doesn’t have a block heat switch anywhere around the drivers area. It has a block heat circuit breaker does it via electric.
I’ve let the webasto run for a *long* time and have run secondary heat on the SMX control panels for the front – galley – and bedroom. All the fans run (the front runs barely) but no heat at all 3 locations.
I also did a test where I turned off the 120V water heater – and then waited a few days and used 12v water heat. That works… the water will get hot with the webasto. Just no cabin heat.
I tried looking in the front of the bus – the “spare tire” compartment. None of the green coolant hoses are hot up there. I also took off the diesel tank access panel ( this is in the entertainment bay – which on our bus is currently empty.) the coolant hoses go through there and are not hot.
Any ideas on where to look next would be super appreciated!
Walt
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11 Replies
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I’m reluctant to make any suggestions since yours is an XLII and mine is an H, but sounds like the heat loop for the heat exchangers is turned off.
Bernie?
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Walt
I’ve read your post a couple times and an trying to follow you on where it’s losing heat. Do these couple things and we can figure it out.
Start with each heat system and run seperately.
Push 120v heat on the panel and run your toe kick heaters. Make sure they work. SMX panel blinking heat light.
Shutoff 120v and push 12v heat only and let the Webasto run alone and tell us what happens.
On your vintage if you look under your motor on both sides whatever valves you see open them.
You have 4 roof airs correct?
Later
bv
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There may be some electric valves on your coach to supply the hot water to the small radiators. If you open the compartment where your Webasto is look behind the Webasto box, and you will likely see a couple of electric valves . Try tapping on those valves with the 12V heat selected, and the SMX controls in aux heat mode (the heat light flashing). You could also have air in the system, if you pull the black egg crate grills, and the access panes over the heat exchangers you should be able to feel the hoses, and tell if you have circulation. There will be small bleeder valves on the heat exchangers that can be opened to bleed off any air in the system. If you are going to bleed the system, start with the furthest one from the Webasto. On some of the XLII’s it is tough to get the panel off to access the front exchanger.
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OK – Let me attempt to do better.
Yes – we have 4 roof airs (Colemans) with SMX panels for thermostats. There are 4. One in the front, one in the galley, one in the 12V Circuit breaker panel area, and one in the back of the bedroom.
When I push 120V heat – and then double click heat on the SMX panel in the galley – the toe kick heater under the dishwasher works. This is the only (that I know of) SMX controlled 120V heater. The bath one operates with the button on the Techlink switch panel.
If I turn off 120V heat and turn on 12V heat… and then turn on secondary heat for the Galley, Front, and Bedroom I can hear the webasto fire up and run for a while. Then after some time, it begins to cycle on and off. During this time, the fans for the heater cores in the front, galley, and bedroom run and blow cool air.
This is a pic of the hoses in the CurbSide Water bay – these hoses get warm to hot (just to be sure, these are like other ball valves right? Parallel to the hose is ON right?
This is a picture of the compartment where the webasto is: the one valve is manual – it’s on, the other is electric. I did try tapping it while the webasto was running – will tap it some more. I have one of these valves on my airstream.
This is a picture of copper pipes that *Seem* like they should be carrying the hot coolant – these are in the Cargo Bay. These pipes are cold when the webasto is running.
I did take off the egg crate and looked at the heater core setup in the galley. There is no on/off valve there – but there is a bleeder valve with a 1/4″ tube hangning off it. I will try to bleed that. The hoses going to the heater core are cold. I can’t “feel” if there is any liquid moving in the hoses, but if I had to guess I’d say there isn’t.
I will crawl under the back of the bus and look for any valves. There are a few in the engine compartment that you could see while stading – they are all on.
I’ll post what happens.
On a side note – I drove the bus today to test out another problem I was having (it seems to be fixed yay!) and the Prevost Drivers AC/Heat worked great.
I will try these tests tonight or maybe tomrrow. It’s dark now, I might have to do the crawl tomorrow.
Thanks everyone for the notes – hopefully we can work it out.
Walt
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The valves you see standing are the ones, ok they are open.
Bleeding the valve might do it.
When you drive with the 12v heat on does it work correctly.
Later
bvsomething is not allowing flow and our buses are a little different, Steve knows your vintage well. If you can’t get it we’ll get on the phone and work it out
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In here are the 2 valves from the webasto – the webasto unit is the lower right traingular patch in the photo. The green hose going up the back wall there seems to be the output of the pump inside the webasto. The green hose goes to a sort of Y – one fork goes to the manual valve and the other fork goes to the electric valve.
With the 12V heat running (the webasto is running too) I tapped the vavle. I also took the coil off and put my screwdriver in there and the coil IS NOT magnetized. So – it’s not getting power. It’s also not hot after the valvue. I noticed the valve said 24V on it. The hose on that electric valve heads back to the engine – the manual valve hose heads towards the front of the bus.
The hose after the manual valve is hot – also, when I close and open the manual valve I can hear the pump in the webasto change pitch. Telling me that it knows I closed and opened that valve.
I saw 2 more valves – the older “screw in” type ones – in the webasto compartment. I put my hands on them and they are both open.
I’m going to tackle the bleeding next – I’ll post when I get the results. If any other ideas come up, please… let me know.
Thanks again!
Walt
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You’re on the right track. Just to recap, you have the following coolant loops:
Heat Exchanger loop for house heat (your problem area):
Dash loop for driver heat that also blends with A/C for temperature control
Water Heater loop from Webasto
Water Heater loop from engine
You also have a pump that moves coolant to the dash loop in order to give you more heat. You should also have a valve that opens allowing the Webasto to heat the engine, but you said you had no dash button, so that may not apply. You do have a block heater controlled at the 120v breaker panel.
You may already know all this, but thought it would be good to identify all the heat functions so you can sort out the various valves.
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Ok, the weather’s been bad (for California) and the kids constantly want to “camp in the driveway” so I took my 1 hour nap window to attempt at least 1 bleed of the lines.
I I turned on the 12v heat, got the heat going with the SMX control pad in the galley – it was easiest to try first – and bled the line. One thing I noticed as that even with the bleeder opened up all the way it was nothing but a slow dribble. Just didn’t seem right.
It got me to thinking could it be that the circulation pump in the webasto is just not pumping enough? I checked the lines again in the curbside water bay and 3 of the 4 are hot. The set (I think they are a feed and return) that go to the galley heat exchanger are real hot in the water bay – but after they travel through the diesel tank hold and get to the main cargo bay- they are cold.
There are only 4 coolant hoses in the curb water bay – I’d expect 6. Are the other 2 for the front just piggybacked onto the Prevost drivers air and go some other route?
I’m guessing it’s time to start changing some parts (the pump?)
where red is the good place to get the webasto pieces these days? I see lots of great articles, but they’re from 8 years ago…
Do s anyone have any sort of schematic that shows what hoses are what?
Thanks again all! Any other notes are appreciated.
walt
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Hi All,
I was able to talk to Leon at marathon for a bit this morning. And we went over this and the entry light. Figuring I needed cheaper heat (our last electric bill went up by 400 from the heat pumps) I’m working on this first. But now I’m sitting in a waiting room so figured I’d post an update.
Leon said there was a pump at the Webasto and a pump in the front compartment. Sounds like 2 pumps total. I knew the front pump wasn’t working – but also didn’t really know that it was part of the Webasto heat System.
Leon said that the pumps are controlled by a relay that was in the back closet or engine control box. Mine was in the master closet. it is relay rdp – but mine isn’t labeled anymore. Making it easier to find.
Anyway there was no input voltage to the coil of the relay so to test if this was the problem I re plugged the relay to the normal closed configuration and viola! Heat works (yay!) but now to find the root of the problem.
Chased the coil input wire up to a techlink relay module and the module clicks and the signal light is on but there is no power at the connector out of the module.
So so that’s why the heat didn’t work – the input power to the relay has failed. Someone was on the right track and changed the black cube style relay – but that didn’t fix it.
I emailed marathon the progress and asked what to do when the techlink relay isn’t outputting voltage – will post when I solve this.
Thanks is for all the info and pointers – getting close on this one.
walt
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The node relays can be purchased and then sent to Marathon to program.
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after an email back from marathon they said that there are fuses INSIDE the techlink relay modules. Opened it up – and there was a burnt out 7.5 amp fuse.
After all that. Wish I knew to check for that first …. But …. Now I do!
Webasto heat works great. Now…. To replace the fan on the front heat exchanger…. That’s next.
Thanks all – problem solved.
Walt
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