steve48
New member
Hi
Been having problems with the VDO Temperature Gauge on a 1985 raw water cooled BUKH 20.
All OK for many years and then it started playing up. Readout was very high - sometimes > 100C, but as it was doing this within minutes of starting, the engine could not be overheating so quickly.
Replaced thermostat, gauge and temp sensor and initially all was OK but again it started playing up. Spoke to Norman at BUKH and he suggested a dedicated 'earth' return from the gauge. This worked for a short while also but gauge now reads full scale immediately on turning instruments on. Reads nil when wire removed from sensor. Should read max when sensor wire is touched to earth which I don't have to do to get full scale deflection. Have swapped old and new sensor to no avail.
Also, what confuses me is that I thought the temp gauge was really a simple volt meter with a 12v feed and earthed thro' the sensor. The temp sensor gradually decreases its resistance as the engine warms up thus giving an increasing readout of volts (or temp in this case). In fact, the VDO gauge has a live feed, an 'earth' return and a third wire going to the sensor. This wire has been replaced with a new run, to no avail.
The engine is not overheating as I have recently crossed the channel under power (F2 - I was lucky?).
The sound warning set up does not work either (diodes gone on pcb suggests Norman) but the Temp Gauge is totally independent of the sound warning system.
Any ideas?
Thanks
S
Been having problems with the VDO Temperature Gauge on a 1985 raw water cooled BUKH 20.
All OK for many years and then it started playing up. Readout was very high - sometimes > 100C, but as it was doing this within minutes of starting, the engine could not be overheating so quickly.
Replaced thermostat, gauge and temp sensor and initially all was OK but again it started playing up. Spoke to Norman at BUKH and he suggested a dedicated 'earth' return from the gauge. This worked for a short while also but gauge now reads full scale immediately on turning instruments on. Reads nil when wire removed from sensor. Should read max when sensor wire is touched to earth which I don't have to do to get full scale deflection. Have swapped old and new sensor to no avail.
Also, what confuses me is that I thought the temp gauge was really a simple volt meter with a 12v feed and earthed thro' the sensor. The temp sensor gradually decreases its resistance as the engine warms up thus giving an increasing readout of volts (or temp in this case). In fact, the VDO gauge has a live feed, an 'earth' return and a third wire going to the sensor. This wire has been replaced with a new run, to no avail.
The engine is not overheating as I have recently crossed the channel under power (F2 - I was lucky?).
The sound warning set up does not work either (diodes gone on pcb suggests Norman) but the Temp Gauge is totally independent of the sound warning system.
Any ideas?
Thanks
S
