Radiator fans not working

[widdowson2008]

i think mike hot wired his scavenger fan not his rad fans, to cool his bum in traffic.

Knew he'd wired some fan up mit switch but thought it was the rad fans.

[helen&tony]

Hi
Agree, Steve...no need to do a thing...Mazda's electrics do it all for you...and if it's not working, fix it...adding things to take the fans out of operating sequence will only end in tears...
The fans are ingenious...several stages of action on the rad fans with and without aircon on, and a scavenger to take the place of forward motion when stuck in traffic, or when parked for 10 minutes or so with a warm engine on a hot day, and re-starting....Nothing more to do!...add switches, and you just may upset the ECU
If the sensors aren't doing their job, they're available in the Club Shop
Cheers
Helen

[teenmal]

Thanks for that, I'm sure you're right but I tried again tonight though and man was it close to the egde, virtually right on hot and no fan cut in. I had a word with a local garage this morning that regulary work on Bongos and they didn't know how to solve this, if it is a problem, as I've just done what they would have done. But they did say Bongo's come in with the fans running quite often after idling outside for just a few minutes sometimes, but that may be down to a less efficient cooling system.

What I find hard to reconcile is that the gauge range should be 75-120 deg. after the mod, so when it's close to H, it must be over the 96 degrees (or is it?) required to switch on the low speed fans. I could take out the sensor and check the resistance again, but it means a re-bleed and I'm running out of ear plugs.

Has anyone wired in a manual switch for the radiator fans? or carried out the temperature gauge mod as I have, if so, do the fans cut in before it feels like it's going to self destruct? I would be more comfortable knowing they do come on before the head gasket lets go and I would prefer not to put the aftermarket sensor back in as fan switch in at 80 deg. is not ideal either as the stat's always closed. Sorry to harp on about it.

Hi,
I seem to remember Daveblueozzie fitting a manual switch,i think he got the info from Wheelquick.

Cheers.

[swampy]

[Re-read through and I'm not convinced you have a problem other than the Mazda temperature gauge. However...............

Which of these have you replaced?]


I've actually replaced both of them, the temperature gauge sensor a while ago and the 2-pin engine temp sensor twice, which may be causing the problem now, but the aftermarket switches too early and the genuine Mazda maybe not at all - I don't know as the fans have never cut in. Both test fine on the bench, but produce a different result
I'm going to invest in an infra -red thermometer and measure the coolant temp. properly with a pressurized system.
The mod on the gauge actually works quite well, as the stat opens at exactly 82 deg. and this corresponds with 12 o'clock on the gauge, if the gauge falls because you force on the fans on (disconnecting sensor) or switch on aircon, the stat closes at just under 12 o'clock. If the temp rises to 90 deg. the gauge has a corresponding increase. It's a good mod I think, far better than a non-modded gauge with a 'sticking point' between about 75 and 115 degrees.

Part of the reason I'm concerned is because I wonder if the fan switching point at design stage with a genuine Mazda working sensor is actually too high in the first place. I know a local garage that deal with Bongo's regularly, they have had a few cooling problems, it seems a lot of head gaskets have a small weep, (mine does) if they are leaking oil on the block, then potentially they could develop a small water leak. E.g. lots of Bongo's white smoke on start up, from my experience with working on motorbikes nearly all my life (trials, racing and road) Temperature differential on an iron block / alu head can cause a small leak into one or more cylinders, (if the head gasket is not sealing perfectly) on start up when stone cold this can cause that initial white smoke which clears very quickly, the worse the leak, more smoke for longer. This can be due to other factors and diesels can white smoke anyway, so this is not always the case.
Anyway, if the cylinder head temp gets too high, because the cooling fans haven't swiched early enough, the temperature differential could prematurely damage an already imperfect head gasket, causing overheating, and this seems to be Bongo's achilles heel. My MX5 for example switches the fans much earlier, but then it has got a tiny radiator.
Just a thought.

[teenmal]

Hi swampy,

You could fit something like this,it will bring on the fans at a preset temperature.


http://www.ebay.co.uk/itm/120897907308? ... 1423.l2649

Cheers.

That looks OK . TM-2 but cheaper.
Not too sure about using it to kick fans in though.
Wouldn't it be preferable to find out what's wrong and fix it, rather than sticking a plaster over the wound?

Hi Ady
Wadya mean 'not paranoid'?

Hi,
The TM4 has the fan relay switching capability,cost about £120.00..

Cheers.

[haydn callow]

I did get a small batch of those(http://www.ebay.co.uk/itm/120897907308? ... 1423.l2649).......binned them.

Got some from China in the end....they look and do exactly the same but have much better quality sensors.....3 are being tested at the moment....feedback is not very good and I will not be selling them....I'm afraid that as with most things ...you get what you pay for......there are some very good "in hose" fan switches available.....But why bother ??? if your Bongo is working properly the fans will switch in/out just fine.......fix the underlying problem is my advice.

If anyone wants TM-4's or any other Oz Watchdog product I can get them cheaper if the demand is there.

[rita]

I did get a small batch of those(http://www.ebay.co.uk/itm/120897907308? ... 1423.l2649).......binned them.

Got some from China in the end....they look and do exactly the same but have much better quality sensors.....3 are being tested at the moment....feedback is not very good and I will not be selling them....I'm afraid that as with most things ...you get what you pay for......there are some very good "in hose" fan switches available.....But why bother ??? if your Bongo is working properly the fans will switch in/out just fine.......fix the underlying problem is my advice.

If anyone wants TM-4's or any other Oz Watchdog product I can get them cheaper if the demand is there.

Hi Haydn,

That is very interesting that you binned a small Batch of this product,could you tell us what was wrong with the product.

Cheers.

[haydn callow]

The quality of the sensors was poor and the way they connected into the unit was very flimsy for vehicle use.....

Again with the ones I got from China....although better they are way behind the products from WATCHDOG in Oz......I will not pass on anything I would not use myself and so far the TM-2 is miles ahead in every dept.......To date ..apart from the odd sensor cable which has been burnt/damaged I have not had a single one fail or a complaint out of hundreds supplied.

[widdowson2008]

Hi Swampy
From what you have said ie: heaters working, no coolant loss, fans not switching on, your system seems to be working just fine.
Other than when using the aircon, the fans will ONLY kick in if/when the engine sensor sees a temperature of 96/97 which is the point at which the thermostat has effectively lost control.
All the fans are trying to do is to reduce the temperature to a level where the thermostat regains control of the system.

A thermal imaging camera is OK but you can't use it whilst on the move. Bit of an expensive luxury IMHO.
For peace of mind, your best bet is to fit a temperature probe. Take a look through the following post for a good/cheap one......
http://www.igmaynard.co.uk/bongo/forum/ ... hp?t=50699
This will tell you all you need to know temperature wise on a 'live' basis.

I have a TM-2 fitted. Invaluable piece of kit and I thoroughly recommend getting one. Not only does it give me an accurate 'live' temperature readout, but it also screams out (very loudly) if there is a coolant loss. This feature was particularly valuable to me when I didn't fit the expansion cap correctly.
Also useful to test the fans are coming on at 96/97 (when bleeding).

[mikexgough]

Mazda repackage a Denso Sensor for the fans..... cheaper from Germany than the UK...
Although there are some "pattern" ones which have the same as the Denso on parameters....
In all honesty..... My fans never run unless I run my Bongo to "bursting" point where it is so hot it would never achieve that temperature in normal use with OAT silicate,borate free coolant like in the homeland.
Red OAT coolant as above boils at 134c ......

[swampy]

That's great thanks, I got an infra red thermometer today (£30 machine mart) and checked the temp at various points on the head, also changed the sensor for another one, this one works! It seems that although they test very similar on the bench, there is a variation when bolted into the head. The genuine Mazda sensor may have worked when very hot, but appeared not to, the first aftermarket sensor switched way too early and this one switches somewhere inbetween. So problem solved, I feel more comfortable knowing the fans will switch on before the my modded gauge actually gets right up to hot.

[haydn callow]

I have a TM-2 fitted. Invaluable piece of kit and I thoroughly recommend getting one. Not only does it give me an accurate 'live' temperature readout, but it also screams out (very loudly) if there is a coolant loss. This feature was particularly valuable to me when I didn't fit the expansion cap correctly.


The TM-2 itself does NOT scream out when there is coolant loss.....the TM-2 is just a temp gauge/alarm.....the system Steve above has fitted is a TM-2/Low Coolant Alarm Combo unit. That system covers almost all possible problems.

[widdowson2008]

I have a TM-2 fitted. Invaluable piece of kit and I thoroughly recommend getting one. Not only does it give me an accurate 'live' temperature readout, but it also screams out (very loudly) if there is a coolant loss. This feature was particularly valuable to me when I didn't fit the expansion cap correctly.


The TM-2 itself does NOT scream out when there is coolant loss.....the TM-2 is just a temp gauge/alarm.....the system Steve above has fitted is a TM-2/Low Coolant Alarm Combo unit. That system covers almost all possible problems.

.....and wouldn't be without it. Bit expensive, .........or is it? Far cheaper than a head by a country mile. Can't speak highly enough (and I have no vested interest in the product - just thankful I've got one)

[rita]

The quality of the sensors was poor and the way they connected into the unit was very flimsy for vehicle use.....
Again with the ones I got from China....although better they are way behind the products from WATCHDOG in Oz......I will not pass on anything I would not use myself and so far the TM-2 is miles ahead in every dept.......To date ..apart from the odd sensor cable which has been burnt/damaged I have not had a single one fail or a complaint out of hundreds supplied.

Hi Haydn,

I am very sorry to hear that you lost money with this product.Did the supplier not offer you a refund,if not I hope you left negative feed back,it might also be worth contacting ebay to .lodge a complaint against the supplier.It looks like the product might be deemed as ""Not fit for Purpose for vehicle use"".

At least you have saved others from losing money all be it at your expense.

Good luck.

[haydn callow]

I did not go the ebay route....in the end I considered them to be poor quality and so went for the ones from Chine which turned out to be little better.....you win some/lose some.....
they were cheap and cheerful and would probably have done the job ...but I didn't feel I could give a warranty as I do with all the products I do sell.