| Author | Message | ||
     John Rowney Experienced User Username: johnrowney Post Number: 160 Registered: 02-2015 |
The external temperature gauge on my 1978 Corniche DRH32489 has been playing up. It works occasionally, but mostly it indicates about -30 deg C (the lowest it can read). In a moment of madness, I have taken off the radiator shell and looked at what I have got installed as the sensor.  The sensor and the associated gizmo enscribed 7K1.  Another view The Sensor is a VDO device with the number 977. I have looked at the Introcar and Flying Spares sites and there appears to be nothing resembling the system I have found. Does anyone have any idea of what I should do? Does anyone know what the gizmo labelled 7K1 actually is? By the way: Now that I have pulled the radiator shell assembly off, the external temperature is reading perfectly!! Looks like I will have to reassemble everything before I get the dodgy temperatures again. | ||
| Alan Dibley Frequent User Username: alsdibley Post Number: 390 Registered: 10-2009 |
John, the temperature reads very low because there is a break in the two-wire circuit from meter to sensor and back. Twiddling the wiring while watching the result at the meter should find it - most probably at a connector. The environment around there is hostile to electrical connections. HTH, Alan D. | ||
| John Rowney Experienced User Username: johnrowney Post Number: 161 Registered: 02-2015 |
Thanks, Alan I fiddled around with the connections and taped over the damaged covers, and the temperature reading remained exact. I also noticed that the gizmo labelled 7K1 had a hole in it corresponding to the hole in the bracket which holds the sensor. So I bolted it on and the wiring looked like it was originally in place there. I put the radiator shell back on and went for a spin for an hour or so - the temperature was perfect! Many thanks for the suggestion. It would be interesting to find out what the 7K1 gizmo is. Perhaps it is part of a wheatstone bridge type of measuring system. | ||
| John Rowney Experienced User Username: johnrowney Post Number: 168 Registered: 02-2015 |
I drove the Corniche a few times since my last posting, and the external temperature behaved itself. However, around Christmas time it played up again - initially indicating about 10 deg C, then after a while dropped instantly to -30 deg C. I took the radiator shell off again and fiddled with the connectors. At times I could get a decent reading, but with a bit of twiddling around the connector, I sometimes got it to work, and at times it failed. Obviously, like Alan's findings, the connector is the problem. I took the sensor out and tested its resistance in ambient conditions (30 deg C) and hot water. As the temperature fell, the resistance increased. So this demonstrates that a poor connection would increase resistance and indicate very low temperatures. I installed a new connection to the wire ex the gauge, used a new length of wire and new connection to sensor, taped everything up and everything now works well. I have put the radiator shell back on and I await some decent weather so I can take the car on a reasonable drive to verify everything is OK. For the record, the sensor has the following markings around the hex section: 801/3/2 Germany VDO 9.77 6-24V 120 deg C I think that the 9.77 might refer to the month and year of manufacture, since the car is a 1978 model. I will let you know how things go if we get any rain-free periods in the near future. | ||
| John Rowney Experienced User Username: johnrowney Post Number: 169 Registered: 02-2015 |
I went for a short spin to the beach and back (16 miles) in the Corniche with the hood down. What a very pleasant drive and the external temperature measurement was spot on. Around 28 deg C. Hopefully no more problems for a while. (Fingers crossed). |
