Triumph Repair: Spitfire electicial surge, electrical surges, battery connections

Question
Hello:

When driving my 77 Spit, it seems as though I have an occasional electrical surges - the blower fan speed increases, the lights get bright, etc. It happens without warning and lasts for several minutes, then returns to normal.  Voltage regulator?  Ay help would be appreciated. Thanks!

Answer
Hi John,
That is one possible cause so you need to connect a volt meter to the battery and keep it in the car so you can monitor the voltage when this happens. There are other possible such as a loss of a battery ground when driving. The alternator tries to charge the battery and this means the current must go through the battery and back to the alternator case by way of the battery ground and the body to the engine and on to the alternator case. If you were to loose the battery ground the current will seek a new rout and if the lights are on and the heater fan are on, these are that ground.
I would check both battery connections and run the volt meter test I advised. Normal charge rate is 13.8 to 14.5v
Let me know,
Howard