new Alternator result in higher Temp readings (Mason fitted)

[sleepwalker]

Hi

just curious. I've recently had a new Alternator fitted and since then my temp gauge (Mason fitted) has always read higher than before the work was done. There are no overheating issues at all and I have been doing motorway journeys of over an hours length for the last 3 weeks without problems. Could the mason read higher generally now i'm getting better output from a new Alternator?

- On old Alternator Temp reading on motorway journeys was just over 50%
- After new alternator fitted temp gauge reading is around 75% on same journey

Thanks

[Simon Jones]

Do you have before and after readings across the battery to compare the alternator output? On my previous diesel with Mason alarm, it tended to run between 12 & 1 o'clock as standard. On my V6, it's 1 o'clock or just past.

The temp gauge uses a circuit known as a Wheatstone Bridge which determines the unknown resistance on the temp sensor by comparing voltage across it to the voltage across a known resistance value. The Mason alarm changes the sensitivity of the gauge by tweaking these values. As a result the reference resistance is very dependant on supply voltage, so yes, that is the answer. What we don't know is whether the output from new alternator is too high or the voltage from the old one is too low. If you've had to fit a new alternator, the chances are the latter of the two options.

[sleepwalker]

thanks Simon. On the old alternator the reading was identical sounding to your Diesel Bongo (i'm Diesel too).
Now I have the new part i'd say its more like 5 past the hour (or 75% ish). Unfortuantley I didnt take any voltage readings.

Thanks. Sounds like its just one of those things really....if slightly disconcerting when it first happens