ECU information required

[widdowson2008]

ps - both fans start together, I thought they might start with 1 fan then 2 if temp not stabalised - save on fuel.

Dont know if this has been mentioned (or if you are aware), but the fans have 2 speeds - low and high - both controlled through the ECU.

Kept out of this lately cos I didnt want to pester 'the team', but are we any closer to deciphering the code/programme James?

[Rhinoman]

are we any closer to deciphering the code/programme James?

Indirectly, the info that Stockportdave is providing is very helpful I nned to hook up my ECU and see what voltages those resistance values correspond to. I'm using the van as my main transport at the moment so I'm loathe to start dismantling it to do tests.

[widdowson2008]

Is it another ECU you need? cos I have one (actually belongs to ebygum if everyone had their own).
If its any use, and providing ebygum gives his permission to pass it on, then would this resolve the problem?
The other thing I was going to ask is do you have a connector to go in the back of the ECU yet? I thought ebygum was going to donate his. If not, I may be able to get one elsewhere.

[Rhinoman]

I can use my spare ECU but I don't recall receiving any connectors.

[widdowson2008]

I can use my spare ECU but I don't recall receiving any connectors.

Would it be of any value?
My thoughts, way back at the start of this, was to rig up something to interrogate the variouse sensors (health wise) as shown in the manual.

[Rhinoman]

I can use my spare ECU but I don't recall receiving any connectors.

Would it be of any value?
My thoughts, way back at the start of this, was to rig up something to interrogate the variouse sensors (health wise) as shown in the manual.

Connectors would be useful, I could the power it up on the bench connected to my test set. As far as I can work out the box shown in the manual is just a bunch of wires with connectors at either end and some test points, there doesn't seem to be any real advantage over backprobing the connectors except ease of use.

[stockportdave]

Thanks chaps -I forgot about the anti freeze re boiling. However, I think it likely that occassionally cars are run without antifreeze - So one would think that the fans would start at a lower temp.

I think thermistor probably OK but am about to use oil to get above 100degC. Yes I did use the cooling down method, Rhinoman, thanks for tip though.

PSI BPoint
14.7 100 atmosphere
16 102
18 106
20 109

ref: http://www.engineeringtoolbox.com/boili ... d_926.html
I wonder what the water pressure is?

Rhinoman - will try and get you a graph of voltage vs resistance soon

[mikexgough]

pressure cap is rated at 1.1.bar or 15.9 psi.....

Also typically the boiling point of 50% OAT Red coolant is 130C....

[stockportdave]

Thanks Mike. I have just tested my sensor at 20degC and at 80degC and sensor is within spec so seems OK. However .....
From inside the Van I have found that the fans start when the resistance of the sensor (using a variable resistor) is 145ohms.

From the table below, which i did on kitchen stove, my fans kick in at about 112deg C. So does this mean that if you do not have antifreeze, you might boil the water !?

Or is my ECU not working correctly, should it turn the fans on earlier?

temp resistance
140 93.2
130 95.8
125 103.5
120 114
115 127.5
110 141
105 157.8
100 178
80 336
65 490

Rhinoman
This table may not be of much use but here it is

voltage res(k)
4.5 11.3
4.2 7
4 5.39
3.8 4.38
3.6 3.65
3.4 2.99
3.2 2.56
3 2.1
2.8 1.84
2.6 1.58
2.24 1.17
1.97 0.944
1.8 0.825
1.38 0.648
Actions
At 3.76V (dropping to) there is a Relay action sound from under the bonnet
At 3.2V there is a relay action sound that comes from the top of the engine towards the back
At 0.65v (145ohms) the fans start to work.
Of note is that the above voltages are present without the ignition on.

[stockportdave]

On a related issue - The water boils if you remove the cap from the filler tank. Does this show that the coolant is very close to boiling all the time and a reduction in pressure sets it off ?? Or is it that, as the engine is stopped (say) the water near the cylinders has become hotter than it normally would?? My head hurts, going for a lay down.

[mikexgough]

I said earlier that I replaced my Temp Sensor as I was not sure of it's condition....and not a leccy expert......the O.E Mazda packaged part was in fact a Denso 179700 0220..... same part is used on many other cars inc Jaguar X series..... I have now found the part from a supplier in Germany at less than 1/2 the UK O.E price for the same Denso part.....

[The Great Pretender]

On a related issue - The water boils if you remove the cap from the filler tank. Does this show that the coolant is very close to boiling all the time and a reduction in pressure sets it off ??

Yes...................... But no..................But yes.........You can boil water at room temp

[2sticks]

On a related issue - The water boils if you remove the cap from the filler tank. Does this show that the coolant is very close to boiling all the time and a reduction in pressure sets it off ??

Yes...................... But no..................But yes.........You can boil water at room temp

Which is why you can't make a decent cup of tea on top of Mt. Everest.

[mikexgough]

The Denso 179700 0220 is used today on the RX8 and the Mazda 2 models.....as well as other makes...

[widdowson2008]

Going back to the origin (and reason) of this post, which was:
Following on (running in parallel actually) from the cooling system investigation, I have aquired from
ebygum8, a second thermostat housing for testing, and on loan, an ECU.
As with the cooling system posts, I know absolutely NOWT about the ECU except that it has some sort of control over the cooling system fans.
I have taken a preliminary look and consulted the manual and have so far come up with the following.

- The ECU for a manual and automatic vehicles are different animals.
- There are 3 banks of terminal pins (automatic) and 2 banks (manual) which connect it to the vehicle - some pins are larger than others.
- from the manual, I see that Mazda have produced diagnostic 'boxes' for maintenance/fault finding purposes, and I see no reason that similar testing gear can't be replicated (probably for use by BF members)

Are we any nearer to determining the ECU/fan relationship? or can we call this a lost cause and draw a line under it?