[paulgato]

I completed the installation of my 2kw coolant heater/pump today, and tried it out this evening. (Woo-hoo!)

I had not driven the car all day so it was stone cold. Ambient temperature was about 9 degrees. (All temperatures mentioned here will be in Centigrade!)

The coolant heater took 20 minutes to heat the coolant to 50 degrees, and a further 50 minutes to heat it to 88 degrees, at which point the thermostat shut off the element and the pump continued to run on its own until the temperature dropped to 78 degrees, then the element switched back on and temperature rose to 88 again. At that (rather high) ambient temperature the 1.8kw heating element was on for about 30% of the time to maintain the 78-88 degree coolant temperature..

I left it to cycle a few times as I was busy doing something else indoors. I finally got in and did a test drive after the heater had been on for about two hours.

I should say that most of my daily driving is on short, local journies of less than 10 miles at low speed, although I may drive 50 or 80 miles total in a day on my way to customers' houses or to suppliers, or to social events etc. in the evening. The engine barely has time to warm up on short drives like that. I live about 5 miles from Oxford and I've often noticed that if I drive into town (with a cold engine) the in-dash mpg display will show an average of maybe 85mpg, but on the way back home - even if the car has been parked up and cooling down for an hour or so - I'll get closer to 100mpg displayed. (The dash average mpg display only shows up to 99.9mpg in fact.) I was never quite sure whether this difference was to do with temperature, or whether it was more that on my way into town I am sometimes in a rush but on my way home I may be driving more sedately. It may be a bit of both, but still 'n' all, I have NEVER got better than about 85mpg on that run into town on a cold engine (much less than that before I stopped using the alternator!) and tonight I got a solid 99.9mpg displayed on the dash both ways.

So, a success I think!

It probably helps a lot that I am not doing all that reversing and manouvering to get off my driveway on a stone cold engine.

I've deliberately not yet tried to install the radio controlled switch for switching the pre-heater on from inside the house. I fitted a manual switch under the bonnet for the time being, just to test out the heater unit before introducing any potentially confusing radio-related variables. Assuming the heater continues to work as expected, I'll try fitting the remote switch thing in a week or so.

One other thing I noticed this evening while the coolant heater was running is that if I try to use the blower to heat the cabin (I would want to use it to defrost the windscreens if it were colder) then the coolant temperature is dragged right down to 58 degrees. That's only 50 degrees above ambient, so at -10 ambient, if I were trying to use the blower to defrost the screens, the coolant temperature could be dragged down to 38 degrees! It turns out that 2kw is not that much after all!

However, I realised that it would be quite easy to fit a power socket and a 230v fan heater in the front passenger foot well. The socket would become live when the coolant heater/pump is switched on. A 1kw heater would be about right, and I happen to have just such a heater lying around somewhere. (Well, it's a 2kw heater but it also has a 1kw setting and I can easily rewire it so the higher setting is disabled. I am limited to about 3kw, or 13A@230v, as that's the most you can run off a normal UK mains plug and socket.) I would only need to use the fan heater if the temperature were below zero (Centigrade!) but using that instead of the car's blower motor would allow the coolant heater to do its job properly and get the engine up to full heat.

So yes, a success I think!

Oh, and I was concerned that the pump might be noisy, but it isn't. It can be heard as a humming inside the car, but from outside it can't be heard with the bonnet closed.

But now I have a problem. My car's dash display only shows a trip average of up to 99.9mpg. I'm regularly exceeding that since I stopped using the alternator, and as the weather warms up that will go even higher. I think I can change my car's display (using VAGCOM on a laptop?) to show litres/100km instead of mpg, and I can't see there would be any such display limit in that case, as the figure would be going down with better efficiency rather than up. I may have to do that soon!