Engine temp sensor location.

[mikelamb]

Hi All,

Firstly thanks to Ian for getting Me into the database quickly last night, it was a big help.

Following on from My post last night. We had success bleeding the bongo today and she is now running well.
A couple of questions though.

1. The rad fans don't seem to come on quick enough, We feel that the engine is running too hot before they kick.

2. The scavenge fan is also very slow coming on, again it would be nice if it came on sooner.

3. After doing a test drive and getting her up to running temp with the gauge showing at about 2 o'clock,(mason alarm fitted) I then switch off the ignition and when I instantly switch the ignition back on the needle goes nowhere near the 2 o'clock mark. Is this normal?

Just wondering how the temp senders work and could they be failing.

Thanks,
Mike.

[apole]

Hi Mike,

Many people on here, reading prior posts, have said their fans rarely come on. Mine can run for an hour whilst in the garage being worked on, and the fans don't kick in so it's not necessarily running too hot.

I have a mason alarm, when I set out and drive around 50mph on backroads for ages, the gauge stays at 12 o clock. Then going on a motorway etc, it may go up to 1 o clock. When I've been heavily loaded and stuck in traffic or going up long hills etc is has gone slightly higher and once when I was idling for ages after a long loaded run the mason started beeping very slowly (mine is set at 3).

What I have noticed is that if you turn off then put the ignition back on the temp gauge doesn't go up very high. However if you are on a run, you stop for fuel etc, then a few mins later start up again the temp gauge will go up and the mason will beep for a few seconds, I think this is heat soak and the engine starting up again and running soon brings it down again.

Hope this helps.

Andy

[jaylee]

Hi Mike, what is your Mason set at on the blue dial, 4.5 to 5ish?

I've come to the conclusion the scav fan comes on as a last resort to remove any ambient temperature in the engine bay caused by the engine.

What you have described seems about right with the Mason on a diesel they can look scary..!
Judging by the temp gauge, mine seems to settle down once it's up to a good running temp!

[Doone]

I've come to the conclusion the scav fan comes on as a last resort to remove any ambient temperature in the engine bay caused by the engine.

That's what I think too. When our Freda overheated, the scavenger fan came on and stayed on for quite some time. Prior to that we rarely heard it. Allan has since replaced just about every part of the cooling system and the scavenger fan is rarely heard.

But whether you can hear it or not, the scavenger fan does not often cut in, and that's normal.

[jaylee]

I've come to the conclusion the scav fan comes on as a last resort to remove any ambient temperature in the engine bay caused by the engine.

That's what I think too. When our Freda overheated, the scavenger fan came on and stayed on for quite some time. Prior to that we rarely heard it. Allan has since replaced just about every part of the cooling system and the scavenger fan is rarely heard.

With the noise of the engine i don't think it will..
Now the Rad fans blow right up against a solid surface so what you are hearing there is the air hitting the radiator fins then dissipating...

[kelv]

Quite right. My scavenger fan is silent, the only way I could check it working was to view it, and to do that I had to run the engine stationary for about an hour at higher revs than idle.
You would never know if it cut in when you were driving,unless the temp guage showed it and that would probably be unlikely if the guage was not modified.

[mikelamb]

Thanks for all your replys, each one helpfull.

I just want to check which temp sender/sensor actually controls when the rad fans come on.

Jaylee, My alarm is set at just over 5. Call it 5.5 for arguments sake.

Thanks,

Mike.

[missfixit70]

http://www.igmaynard.co.uk/bongo/forum/ ... 7&start=30 page 3 halfway down, Dandy & G8DHE's posts.

Been doing a bit of scavenger fan testing today (call it a student project and you can work on yer own van in College time )

Removed the fan sensor wire, ignition on - fan didn't come on!
Temperature in the workshop 20 deg. C
Tested the sender resistance - open circuit!
Heated up the sensor with a hot air gun - still open circuit - then noticed a flicker on the ohmeter
Tested "A" terminal of the loom connector for the sensor - 5.1 volts as expected.
Shorted the loom conector - scavenger fan ONLY came on and stayed on for several minutes, even with the shorted connector removed and the ignition OFF
Reconnected everything and applied a heat gun to the sensor - at approx 31 deg.C, the scavenger fan ONLY came on, and stayed on for several minutes, longer if more heat was kept on the sensor, but only with the ignition on (The radiator fans work okay with the A/C switched on)

Conclusion: This is a complex piece of kit. The sensor on the centre console the handbrake only "flicks" on for a second, enough to tell the ECU to close the circuit for a predetermined time. The circuit only works on 4.5 to 5.5 volts (most ECUs do).........don't fer chrissakes ever feed battery voltage to it!
IMHO - leave well alone and don't bypass/mess about with it - it involves more than one circuit.

PS - students bored by the first test..........

PPS - tried it again - this time applied more heat to the sensor - at roughly 50 deg.C the scaavenger fan came on and stayed on even wit hthe sensor disconnected and ignition off for around 5 minutes.

PPPS - students now threatening suicide

I would support DW comments about the input side of the ECU it will most often be 5 volt powered. However the Fans themselves are relay switched by the ECU, so it is reasonable to play with 12 volts on the relay contacts side.
The two radiator Fans are interesting devices,the diagrams show them as having two sets of brushes each - one set is powered via the ignition switch and controlled by the ECU and the other sets along with the scavenger Fan are connected on the live side of the ignition via there own fuses and again controlled by the ECU, in total there are 4 relays controlling the 3 fans. So that may well explain the oddities you were getting DW with the temperatures and ignition switch, the ECU can override the Ignition switch if it needs to!

Edit later:- Its even worse than above, one set of relays control the +12Volts to one set of brushes and the the other relays control the ground connections to the other brushes so there are lots of permutations - and I am certain it will vary between versions of the vehicles as well to add a bit more spice

Confused yet

[mikelamb]

Thanks Kirsty, Obvious now! (Do you know which one it is then?)

[missfixit70]

If it's the scavenge fan it seems it's the one Stilldesperate pointed out on the other thread you asked on - http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=33649

This is the sensor



It's not simply a case of connecting across the two wires.

This is from memory. Disconnect the plug from the sensor (A blue and a yellow wire?) (It needs "pinching" to release it), Then start the engine. I used a metal paper clip to momentarily connect across the plug, and you hear the fan running. If you stop the engine, the fan stays on for a few minutes.

Sorry this isn't too technical, if you don't get the results I describe, let me know, and I'll do some more accurate checks on mine to make sure of the sequence.

Hope this helps

SD

But it depends what it is you're trying to solve, I've lost track, you've got so many threads on the go

[missfixit70]

Your problem seems to be the actual temp sensor that feeds the info to the temp gauge & mason alarm IMO ( if any problem) - which is this one http://img216.imageshack.us/i/temperatu ... 039kg.jpg/
as described on this thread
http://www.igmaynard.co.uk/bongo/forum/ ... ure+sender . Purely because you say the Mason doesn't go back up after switching off & back on again. Is this switching the ignition on, or actually starting it again? i think maybe you're getting overly paranoid, unless you're really working the engine, the fans don't do a lot. When you say 2 0clock on the temp gauge, it's difficult to get an exact idea of where that is - a photo would help. 5 to 5.5 does seem high for the mason though, hence my suggestion to check the connections & sensor that feed the info to that first.

[izwyz]

if it works as i THINK it does the resistance of the sensor should change as the temperature changes allowing the ecu to switch in/out the fans as req via various relays etc. but i may be wrong

maybe put a meter across the sensor to check if it is faulty dont know if anyone on here has any figures to compare to?? if not perhaps a trip to a garage for peace of mind.

some cooling systems can run pretty hot my landie for instance doesn't cut the fans in untill 103 degrees



Izwyz

[mikelamb]

Kirsty your right, I am confusing matters here! Gone from one thing to another without really making much sense!
I will try and clear things up and hopefully not make things worse.
My mason alarm is set at 5.5 but at the moment is quiet. The needle on the temp gauge goes to within (just fetching tape measure be back now!) 2.0mm from the first white line on the gauge. On a climb it will go to the line!
Now onto the temp sender. The one I would like to change is the one that controls the temp gauge. Does this one also set the rad fans in motion?
The annoying thing is, is that the van is going well and the engine sounds sweet! The only thing thats making Me worry is the temp gauge! I suppose that without the mason alarm I would be less aware of the gauge but then would leave Myself wide open to a overheating episode.
I am thinking of getting a tm2 and placing it on the van so that I could compare with other readings from Members on here.
Hope that clears up some of the confusion I have created!
Thanks for your patience,
Mike.

[missfixit70]

Ok you need to turn the Mason alarm down to around 4.5 so that it goes off on a long climb then just tweak it up a bit.
Adjusting the Mason does not change anything to do with the temp gauge.
The mason seems to be doing exactly what it should, if it's ONLY going to the first white line past 12 0 clock, that' is exactly as it should, it increases the range of the existing temp gauge. If it goes to the red, you have problems.
Stop worrying & get on & enjoy the bongo
Why do you want to change any of the senders? the one that controls the temp gauge is nothing to do with the ones that control the fans, look back through this thread, I've answered that question somewhere in all that lot already

[missfixit70]

You have a pm