prawnabie
|
| posted on 15/6/10 at 07:13 PM |
|
|
Fan switch issues...
Hi guys
Can anyone give me a hopefully easy answer to the following puzzle!!
I have bought a 97-92 degree fan switch. I tested it in a pan of boiling water and the contacts closed at 99 degrees and opened again at 91 which was
good enough for me. I repeated this test 3 times in succession and all was OK.
I have installed the switch into the alloy housing in my top hose and the contacts now open and about 86 degrees?!?!
I had my previous "adjustable" switch set to 97 degrees measured via a digital thermomter at the same place I am measuring the temp with
the new switch in so I am pretty sure I am reading the same temp.
Can anybody offer an explanation as to why the new switch makes the contact at 97 in a pan of water and 86 when on the car??
Thanks
Shaun
P.S I am just going to test the adjustable one to make sure it opens at the same temp in the pan of water as it did on the car.
|
|
|
|
|
austin man
|
| posted on 15/6/10 at 07:14 PM |
|
|
the pan water is'nt pressurised, you may have an airlock causing pressurised steam
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
|
|
|
britishtrident
|
| posted on 15/6/10 at 07:33 PM |
|
|
I take it 86 degrees is the temperature on the outside of the alloy hose adaptor, not the rad hose.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
prawnabie
|
| posted on 15/6/10 at 07:49 PM |
|
|
Thanks for the replies
I have been measuring the temp on the car with a probe type digital thermostat on the head next to the temp sensor (just below the stat). I have used
the same place to measure the temp with both switches. The temp readout was within a few degrees of my acewell dash although the acewell was slower to
react to temp drops when fan was on.
I have just tested the temp that the adjustable one switches on at. (the adjustable one is a revotec digital one with a POT to adjust the switching on
temp).
At the posistion it was set to (came on at 97 degrees as measured on the car as above) it didnt come on at all even in the pan boiling water!! I had
to turn it back a quarter of a turn to get it to come on.
This means my acewell and the point a which I was measuring the temp on the car is inaccurate and the rad fan switch is switch on at the right
temp!!
Now the reason I did all this in the first place...
When driving at 50+ the acewell indicates 82-85 degrees with is the opening temp of the stat. When doing 30-40 it will creep up to about 88 on the
acewell. Within a minute or two of parking the car and turning the engine off the fan will always come on. This makes me think temp the fan is
switching on is too close to the operating temp of the engine. Will fitting a 105 degree opening fan switch be too hot for a crossflow engine?
Thanks and sorry if I have confused you!
|
|
|
SteveWalker
|
| posted on 15/6/10 at 09:45 PM |
|
|
Don't forget as well that mechanical switch mechanisms suffer from stiction. The pressure on the mechanism will keep increasing until it finally
flips over, but when it's on an engine and vibrating, it'll flip over more easily, so at different temperatures.
|
|
|
.jpg)
