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Re: Temp gauge reading with Mason alarm.
Posted: Wed Aug 13, 2008 3:36 pm
by dandywarhol
Found the problem - temp sensor in head on it's way out - I guess a higher resistance made the gauge show cooler. Removed the wire to check sensor resistance and found the spade on the sensor loose - needs a new one as it's now knackered

Re: Temp gauge reading with Mason alarm.
Posted: Wed Aug 13, 2008 3:37 pm
by dandywarhol
Re: Temp gauge reading with Mason alarm.
Posted: Wed Aug 13, 2008 9:48 pm
by cheffy34
Re: Temp gauge reading with Mason alarm.
Posted: Wed Aug 13, 2008 10:55 pm
by dandywarhol
I reckon there'll be some variance in even similar engines cheffy. Cooling systems are designed to work at an optimum temperature and the system is designed around that. I don't think there'll be much difference between a Mazda 2 and a V6 but there could be a difference in the signals from the gauge sensor. Dave Mason would know more about that I think.
Re: Temp gauge reading with Mason alarm.
Posted: Thu Aug 14, 2008 8:57 am
by Dave Mason
dandywarhol wrote:I reckon there'll be some variance in even similar engines cheffy. Cooling systems are designed to work at an optimum temperature and the system is designed around that. I don't think there'll be much difference between a Mazda 2 and a V6 but there could be a difference in the signals from the gauge sensor. Dave Mason would know more about that I think.
No, sorry, I really know nothing about those engines. I'm more into electronics and my vehicles are Toyotas (Townace, Yaris, both Diesel).
The temp gauge sensors in the engines are just special resistors that reduce their resistance from over 1000ohms to under 100ohms as they are heated up. Nothing complicated but the range of resistance could vary if a different spec sensor is fitted (or if it's faulty).
Apart from the audible alarm bit, the Mason alarm (and I've only ever sold one version for Bongos) also has a simple action - when the sensor resistance drops to a certain point (i.e. the engine temp goes up to a certain point) the Mason alarm switches a shunt resistance across the sensor which fools the gauge instrument into "thinking" that the engine has got a lot hotter and the sensor resistance has gone lower. The "certain point" and the value of the shunt resistance have been selected (with help from Bongo owners) so that this trick bypasses the dead zone in the middle of the gauge instrument's range and, as the engine temperature continues to rise, the pointer moves smoothly on up the dial instead of sitting near the middle, grinning at you, saying "you think your engine temperature is nice and steady but actually I'm just pretending - you haven't a clue what's going on".
So, the fact that Cheffy gets "substantial movement" in the upper half of the dial suggests that the standard Bongo Mason alarm is having the right effect in his V6 and that it has same type of sensor, and temp gauge instrument, as the others.
By the way, my summer vacations are over so there should be no delay despatching Mason alarms now. See
http://www.townace.plus.com/ie/ietemga2.htm
Re: Temp gauge reading with Mason alarm.
Posted: Thu Aug 14, 2008 10:19 am
by jaylee
Hope you had a good break Mr Mason.
Looks like yer gonna be posting one more, i just ordered one!
Just done the Poland trip & have the constant 11 o clock reading, now occaisionaly my centre console got warm in the early miles of a 200 odd mile run then stayed relatively cool.. (even during a couple of long traffic jams!)
No loss of coolant.
With regards to over heating history;
I have a slightly opaque header tank, but i had a similar thing with a diesel Vauxhall Combo van i owned for 13 years, having been only a year old when i bought it, i had no trouble apart from the radiator bursting from some 6 or 7 years of chaffing at the back.. (a design fault rectified with a new radiator mod by vauxhall).
Lucky it was just stood idling at work at the time, & a colleague noticed water running out the bottom, so it did no other damage.
After that, it carried on to serve me well! (even though i didn't trust the temp gauge on the Vauxhall either)...
Does anyone have advice regarding fitting the alarm?
What should i be careful with?
(Apart from the thin wire thing @ the back of the temp gauge.)

Re: Temp gauge reading with Mason alarm.
Posted: Fri Aug 15, 2008 4:17 pm
by jaylee
That was damn quick dispatch Mr Mason, just got the alarm in the post this morning!!
Cheers!!