[Tf175]

Need some help on getting working the engine pre-warmed on cold temperatures, the coach has been sitting for a few days in 20-30s and the lakes around us are frozen already so it is cold I was looking at the pre-heat switch but is not working as a on-off switch it only works as a toggle so not sure if by toggling starts heating the engine and also how do I know that it is working? Does this works by being connected to shoreline power? I should have tested this before but never occurred to me that the switch will be a toggle (it could be broken). I will be a few more days here so if I have to swap the switch is good to know how.

Thanks in advance for any help

I'm not sure about your 88 , but on the 86 there is a 110 outlet on the bulkhead , passenger side engine bay . The engine heater plugs into the outlet which is controlled by a regular switch ( as in light switch ) in the bedroom . There is also a thermostat behind the temp/barometer above the door . If your's has the outlet in the engine bay , you can plug a light or tester into it with the switch on to check for voltage . The engine has a lot of mass  and will take some time to warm ( my book says hours) . It's working if the engine block starts to feel warm to the touch after 2 or 3 hours  , it's working . I'm a rank beginner , but that's the way the one here works .
Good luck .