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Barely any Dash Heat
I recently overhauled my Webasto and also replaced both of the coolant pumps that sit behind the Webasto box. I did some very cold mountain camping over Thanksgiving and that whole system works awesome.
The only issue I had was the drive to the NC mountains in that nasty cold weather early Thanksgiving morning. I had the dash heat on, set to full-hot and recirculate. I have a switch on the panel below the radio that is A/C clutch one way and “Circulation Pump” the other way and that was on the circulation setting.
The best I could get at highway speeds was barely warm air. I wound-up having to run the Webasto the entire 10-hr drive to stay warm. I would have thought that 8V92 would melt the pola cap!
Anything come to mind? My only thought was that the Circ-Pump switch connects to a 3rd pump somewhere and that pump is as dead as the other two pumps were???
Thanks
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9 Replies
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Liam,
Are the circulation pumps working, and if so are the valves open? The Webasto will not fire the burner if the coolant temp is in excess of about 160 degrees.
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Jon, both pumps with the Webasto are brand new and working. When I flip both overhead switches on, the webasto fires, the pumps run and I get wonderful heat through the 3 converter-installed exchangers.
I am not getting heat from the Prevost dash heater while driving (2 overhead switches off and factory recirculation switch below radio on)
As I understand it, the factory dash heat & defroster work from a factory installed heat exchanger based on engine heat – independant of the Webasto system. I assume because there is a seperate circulation switch that there must be a seperate pump in addition to the two with the Webasto??
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Your dash heat is independent of the Webasto. Providing the valves in the engine compartment are open, when the engine is running coolant circulates to the front by action of the engine water pump. Most converters have a supplemental pump to move coolant quicker to the front providing more heat. You also have a blend valve up front just like a car that opens or closes as you dial in more or less temperature.
So, the place to look are the valves in the engine compartment and the blend valve up front. If the supplemental pump doesn’t work, you should still get heat, but not as hot as it would be running. The blend valve is usually located behind the bumper up high and has coolant hoses attached with electrical wires. I had to replace one on a prior bus because the heat temp knob on the dash had no effect on temperature and the solenoid was bad.
Hope that helps.
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My bad, and I should have known better. I assumed a Webasto installation would be tied into the coach coolant system so when needed the engine block could be heated. That is why I mentioned the Webasto circuolating pump.
Tom is right about the Prevost circulation pump.
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No worries and thanks as always! When I was at Elite, Tom took me into the pit for a guided tour of my underside and I didn’t remember seeing a third pump – but in my mind there absolutely must be one. I guess the other question is whether doing the replacement of the two Webasto pumps they turned-off some valves to preserve coolant and forgot to turn them back on. At least when I go back to the shop I will be smarter.
In any case, I am learning the lesson that even if you don’t happen to need things like the Webasto as we rarely dry-camp, it has to get used or things like the pumps will freeze up.
Real answer is I need to retire so I use this stuff all the time 🙂
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Check those valves Liam, it’s not unusual to find them closed. I close them in the summer to make sure I don’t have coolant running through the loop and effecting my dash air. If that blend valve goes bad, sometimes it won’t close off the loop and your dash air won’t be as cold as it should.
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Liam, I had a ’90 CC with the system you describe. If the dash heat circulation pump was running I could get all the hot air I wanted at the dash while driving in temps down to about zero degrees. It sometimes got so hot even at the coolest setting that I had to shut the circulating pump down periodically. Either your pump is not operating or the valves at the engine are closed. I have no idea where that circulation pump is located, but I do not recall hearing it run. One thing to note, we had to switch on both the Webasto burner and the Websato pump switches to keep the whole bus warm while driving when it was real cold. Sometimes the Webast burner would kick on while we were driving to augment the heat generated by the engine, and as you noted the 8V-92 is not shy about heat production. Good luck.
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Thanks for all the advice – I will do some more detective work and report back.
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Liam good chance your engine recirculation pump is located in the center channel of the first bay. Have the switch on and lay in the bay you might hear it run. If your engine gate valves are closed that pump can run all day and it will not push in coolant. Your Gate valve off the engine should be in a little door or flap on the left hand side of the radiator after you open the radiator door. Remember this circuit was put in by Prevost and the house heat circuit by your coach converter, so they are two different loops.
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