temp gauge gone mad...

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Russell Jupp
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temp gauge gone mad...

Post by Russell Jupp » Sun May 17, 2020 8:50 pm

Evening all,
just after a little help please?
1999 2.0 petrol. Drives fine. No coolant loss. Not overheating.
But, within 30 secs of starting from cold, the temp gauge climbs up to normal.
As soon as I start driving it creeps up to just over 3/4, then gradually drops and stays steady at 3/4
Also both rad fans seem to have a mind of their own. More often than not they are continually running. Even when van has been left overnight. Air con is off.

Im guessing the sender for the gauge?
Not sure about the rad fans tho.


TIA
Russ
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g8dhe
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Re: temp gauge gone mad...

Post by g8dhe » Sun May 17, 2020 10:14 pm

The dashboard temperature sensor (1-wire) only drives the gauge and it isn't unknown for it to have connection problems its a single Green wire at the front of the engine from the drivers side.
The fans are controlled by the ECU which has its own temperature sensor on the side of the engine block with a 2-wire connection.
There is also the scavenger fan that has its own sensor and which cools the engine housing under the seat, this quite often gets disconnected and means that the scavenger fan turns on/off at unexpected times as its working in fail-safe mode controlled by the ECU again.
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Re: temp gauge gone mad...

Post by Ian » Mon May 18, 2020 8:13 am

This from the Bongo Clinic on main BF website:

Q: Can you explain what the different fans are for? I understand that there are radiator fans, and a scavenger fan? What do they do? (Barry from Monmouth)

A: The Scavenger fan is the one situated directly in front of the engine pointing upwards, it pushes air through the engine bay. It mainly comes on when static and the normal airflow has stopped hence causing the engine bay itself to heat up. It is controlled by an air-input sensor. The engine cooling fans are the ones behind the radiator which draw air in to cool the radiators, they also come on when the air con is selected to ensure that the air con radiator receives sufficient cooling. They are controlled by a temperature sender unit that sits low down on the cylinder head.
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Russell Jupp
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Re: temp gauge gone mad...

Post by Russell Jupp » Mon May 18, 2020 10:20 pm

Thanks guys.
Noticed something even more odd today. The plot thickens....
Approx 1min after engine start, the temp gauge shows just under halfway.
The coolant can't possibly get to that temp in such a short time?
It stayed like that for about 2 miles, then suddenly shot up to just below HOT.
Stayed like that for a minute then rapidly dropped to just over half way - and stayed there.
There’s more....
Got home. Switched the engine off. And instantly turned the ignition on again.
The gauge climbed to just under 1/2 and stayed there.
As soon as I started the motor it climbed back up towards HOT and settled.
Very odd.
I checked the sender at the front of the cylinder head. Secure and clean. Disconnected it and the gauge stopped working.
Incidentally, I’ve found the rad fan sender. If it’s the one halfway back the block, drivers side....
But it’s only a single wire connector and disconnecting makes no difference to the fans.
Thanks again
Russ
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Re: temp gauge gone mad...

Post by g8dhe » Mon May 18, 2020 10:36 pm

The scavenger fan sensor is a two wire B3-09 mounted under the middle of the handbrake lever and pointing down inside the engine housing ?
The only thing I can think of around the handbrake with a single wire is the handbrake switch at the very rear of the handbrake.
The engine coolant sensor feeding the ECU in the side of the engine is also a 2-wire B3-11
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Russell Jupp
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Re: temp gauge gone mad...

Post by Russell Jupp » Tue May 19, 2020 12:09 am

Thanks Geoff.
I found the scavenger sensor. Disconnected it and the fan started. So that one is ok.
But the sensor halfway back the engine and approx halfway down, on the drivers side is a single wire terminal onto a single connector sensor.
Odd.
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Re: temp gauge gone mad...

Post by g8dhe » Tue May 19, 2020 8:55 am

Not quite sure what you have found as the sensor on the engine, what colour wire is it that you have found, I may be able to locate what it is from that.
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