[Vwdiesel] Cooling issues

[Roger Brown]

Rudy wrote:
> My 1984 Jetta runs about 20 degrees warmer when I have the lights and or
> wipers on (Seattle), I've watched this and its consistent.
>  
> Thought maybe it was the alternator water pump belt but the power steering
> belt is tight and can't slip, they both power the water pump.
>  
> I'm wonder if the added load on the alternator could make that much
> difference in the running temp or does something sound not right?  I saw
> some posts about this a little while back but can't find them now or don't
> know how to find them I should say.  Anybody have any thoughts on this?  
>  
> Rudy

Here was a reply from 10/17:

> At 06:26 PM 10/17/05 -0400, you wrote:
>> >I was wondering why my temp gage reads slightly higher when driving at night
>> >with the lights on. During the hot summer days it runs just barely touching
>> >the center line on the gage but when I drive into work in the morning or
>> >coming home in the dark the needle runs straight up on the center line.
>> >This morning really got me because it was our coldest this year at 45 F/ 7.2
>> >C and it ran the same slightly higher in temp and I even was running the
>> >heater inside the car. Could it be due to the difference in the electrical
>> >voltage due to the draw of the headlights being on putting more of a load on
>> >the alternator? Or even the extra heat in the dash from the dash lights????
>> >Just seems odd to have two different readings.
> 
> 
> This common phenomenon has been noted by others on the forum, as I learned
> after asking the same question last year.
> 
> Manifested as guage showing lower temps in hot weather, and higher in winter.
> 
> In summer, the hot coolant from the end of the head passes through the
> heater core, where it does not lose any heat, because you have the heater
> door closed for cool air. This allows coolant to return to the waterpump
> without any significant cooling, where it hits the thermostat element
> directly, causing it to open a little further, resulting in lower head
> temperature.
> 
> In winter, with the heater going full blast, the returning coolant is cooler
> when it gets to the thermostat, causing it to close a bit, resulting in
> higher head temperature.
> 
> I would find it difficult to believe the volks engineers did this with
> intent, rather, the return from the heater fortuitously impinges directly on
> the thermostat control element, giving you a little more heat in winter when
> you need it.
> 
> Sandy
> My rational on it is, 


-- 
    Roger