Diesel cabin heat assist(webasto)sometimes work and sometimes not, although the temperature is about 2 degrees.I also have a problem with the heating (passenger side blows cold air and the driver side slightly warmer even after one hour drive)

If your Cancun lazy spa is not heating past 38 degrees Celsius (100.4 degrees Fahrenheit), there could be several reasons for this issue. Here are some troubleshooting steps you can try to resolve the problem:

1. Check Water Circulation: Ensure that the water is circulating properly in the lazy spa. Make sure the water pump is functioning correctly and there are no blockages in the water flow.
2. Water Level: Check the water level in the lazy spa. If the water level is too low, it can affect the heating process. Ensure that the water level is above the minimum level required for proper heating.
3. Heater Unit: The heater unit may be malfunctioning or not working at its full capacity. Check for any error codes or indicators on the control panel. If there are error codes, consult the user manual to determine the issue.
4. Temperature Sensor: There might be a problem with the temperature sensor. If the sensor is not accurately reading the water temperature, it could prevent the lazy spa from heating properly. You might need to replace the temperature sensor if it's faulty.
5. Electrical Connections: Ensure that all electrical connections are secure and there are no loose wires. Faulty connections can lead to heating issues.
6. Power Supply: Make sure the lazy spa is receiving the correct power supply. It should be plugged into a dedicated power outlet that can handle the load required for heating the water.
7. Ambient Temperature: Cold weather can impact the ability of the lazy spa to heat up efficiently. If the outside temperature is significantly colder than the desired water temperature, the heater might struggle to maintain higher temperatures.
8. Thermal Blanket or Cover: Use a thermal blanket or cover designed for lazy spas to help retain heat. This can prevent heat loss and assist in maintaining the desired temperature.
9. Filters and Water Quality: Clean the filters and ensure the water is well-balanced and properly treated. Poor water quality can affect the heating process.
10. Timer Settings: Check the timer settings on the control panel. Sometimes, the spa might be set to a lower temperature or a timer might be restricting the heating.
11. Reset: Try resetting the lazy spa by turning it off, waiting for a few minutes, and then turning it back on. This can sometimes resolve minor issues.

The air from the heater core will be as hot as the coolant temperature of the engine. 80 Degrees is the opening temperature of the thermostat and that will be where it remains until the engine starts to work or the ambient temperature rises.
Thermostats come in a couple of different opening temperatures so check around for one that opens around 85 degrees if you want hotter air in the cab
Another point is to close the recirculating vent door to the cabin as the heater core is trying to heat fresh freezing air if it is open

This is totally normal. All radiators contain an antifreeze/ antiboil component when filled as per manufacturers instructions. This stabilizers the temp of the coolant, reducing fluctuations in temperature. The thermostat is heat responsive. Basically a piece of spring steel heated to a temperature then cooled, so as to retain the memory of when to react. Replacing the water temp sensor on this occasion was probably unnecessary, tho in saying that, I have replaced mine & friends with beneficial results.

System is functioning normally at this time, no action is required.

sorry I can't give you a hard fast answer because I am having 38C days and can wear T shirt 12 months of the year, but check your thermostat first, if stuck open it will never get hot, check for blockages in the heater hoses and lastly, your tap operation

By "normal operating temperature", are you referring to the engine temp or the cabin temp? If cabin temp, the defrost selection also engages your air conditioning system which lowers the temperature and the humidity of the air blown through your heating ducts. Although, you should not have to wait 40 minutes for warm air to flow. Check your engine's coolant level to ensure that it's filled properly, and be certain that the temperature control selector is set to the warmest level possible. There are other possible malfunctions that could account for this condition, but we'll leave that alone for the present. Now, if you're talking about the engine's normal operating temperature, please disregard what I have said so far and reply back.

1) The "heat" cycle on a vehicle depends on the engine's operating temperature when "heat'' desired," as well as the "external temperature of the atmosphere; colder days will create "lower" internal temperatures for the vehicle's passenger compartment as related to the amount of cooling of the radiator fluid through the radiator.
2) One option exists as to place "a 'piece of cardboard' in front of the radiator itself," especially in very cold areas of the country.
3) The other problem may involve your "thermostat" of the vehicle being "bad" (they fall apart sometimes), versus being of the wrong temperature variety; In this case your "automotive technician" should be consulted so as to replace your vehicle's thermostat with a different thermostat.
4) Lower temperature thermostats (185 F) open the system to the engine at 185 degrees; with 195 F opening the system at 195 degrees.
5) One of these solutions (the cheapest being the cardboard) may be of assistance (just remember to remove the cardboard in the summer/spring).
6) As of 03-09, 2019 @ 1448 CST; I'd like to add this comment to my above earlier data: It's "best" to never "change" the thermostat rating (exampled from a 185 to a 195; even vice versa) on your vehicle. Simply use the cardboard, removing it with warmer weather.

1-your thermostate is stuck open half way. thermostate is a simple device that made of enlarging metals when heat is applied. it suposed to be in close position to allow engine heat up, when specified temp reached it opens and let it flow and radiator tries to keep coolant cool.when it is broken it stucks or it acts slow or it wont acts at all. in your situation it is stuck open half way. it allows enough water to be heated but flow is limited to heat cabin heater.

2-if there are cabin heater selenoid/selenoids for two different temperature for cabin left and right, on some instance those selenoid valves to adjust cabin heater stuck open or closed like thermostate acts on first case. so heat is not enough to heat up cabin heater.

Hi Joanne, dont know a big pile about cars but I also have 2003 Voyager and I know that this is caused when your heater is up fully. There should also be a whining noise. There is some system in the Chrysler that uses diesel to assist your heater. This causes this series of events when you stop your car and is nothing to worry about. On the subject of heating, my heater is **** and doesnt seem to be enough to heat car. Hope this is helpful. C Burns

Check your fuses first.Does the temperature gauge read normal operating temperature (at least 80 degrees Celsius) if not replace your thermostat.  Does the car have any heat while driving at higher RPM's? If so then you have a bad circulation pump. There is also a hot water valve (mono valve) that could be stuck in the closed position and not letting any hot water flow to the heater core.