Quote Originally Posted by p38arover View Post
I had a call today to help out a chap whose P38A wouldn't start. He owned a Fault Mate but his laptop was dead so I took my laptop which has Faultmate installed.

When I got there, the car was on charge. I plugged in Faultmate and, without doing anything else, the car started. But it smelled very rich and was running very roughly. No faults had been recorded so I had a look at fuelling but, having no idea what I should be reading, it didn't help.

However, during the checks, I noticed the alternator voltage looked too high. It was 16 volts. I wonder what the affect of that would be. He said the alternator was an aftermarket replacement and the battery had been replaced.

I suggested he have the battery tested. I wonder if the battery was failing, could its impedance rise and the charging rise commensurately?
Hi Ron, and 16v is WAY too high.

As long as your mate has only been doing short trips, no longer than about 10 minutes, his battery may be OK.

But even one long trip at 16v is going to damage the battery, and if it is an AGM cranking battery, it will quickly destroy it.

P38s are pre SMART voltage alternator operation and were set up for wet ( flooded ) type batteries and as such, 15v would be the absolute maximum voltage, and this is still too high for continuous operation.

A runaway alternator ( No earth connection ) will charge at up to 18v, so it is more likely a poor earth connection somewhere, or a faulty voltage regulator.

I would start by checking the engine block to chassis earth first, and I have no idea where this is located on a P38.