Ric
Well-Known Member
If I draw a very small current from the alternator D+ terminal, will it have any consequences for the alternator regulation or performance?
I have recently fitted a NASA EG-1 exhaust gas temperature monitor, and have been experimenting with the most convenient way to connect it and use it. I initially powered it from the engine battery master circuit (actually B+ on the alternator for convenience). However, I found that after turning off the engine (but leaving engine battery master on) the temp in the exhaust would climb to a level high enough to trigger the alarm due to residual hot exhaust gases and no more cooling water flow. Increasing the alarm threshold did solve the problem of an alarm after shutdown - but then the monitor would not be as sensitive or useful in its intended role while engine is running.
I therefore powered the instrument from a lead from the ignition switch, so that as soon as the engine is stopped and ignition is off, the instrument would be off, expecting no more false alarms. However, this still did not prevent alarms on engine restart shortly after shutdown, because it would take a second or two for the coolant water to cool down the exhaust.
I am therefore thinking of powering it from D+terminal of the alternator. The instrument would thus only come on once the alternator was spinning fast enough to produce 14v, by which time coolant would have cooled down the exhaust system, so I could set the alarm at a low level without getting unwanted false alarms.
The only issue I have is lack of understanding of alternators - will a small current draw from the D+ terminal have any consequences for alternator output or regulation? I don't think it will - but over to the experts.
I have recently fitted a NASA EG-1 exhaust gas temperature monitor, and have been experimenting with the most convenient way to connect it and use it. I initially powered it from the engine battery master circuit (actually B+ on the alternator for convenience). However, I found that after turning off the engine (but leaving engine battery master on) the temp in the exhaust would climb to a level high enough to trigger the alarm due to residual hot exhaust gases and no more cooling water flow. Increasing the alarm threshold did solve the problem of an alarm after shutdown - but then the monitor would not be as sensitive or useful in its intended role while engine is running.
I therefore powered the instrument from a lead from the ignition switch, so that as soon as the engine is stopped and ignition is off, the instrument would be off, expecting no more false alarms. However, this still did not prevent alarms on engine restart shortly after shutdown, because it would take a second or two for the coolant water to cool down the exhaust.
I am therefore thinking of powering it from D+terminal of the alternator. The instrument would thus only come on once the alternator was spinning fast enough to produce 14v, by which time coolant would have cooled down the exhaust system, so I could set the alarm at a low level without getting unwanted false alarms.
The only issue I have is lack of understanding of alternators - will a small current draw from the D+ terminal have any consequences for alternator output or regulation? I don't think it will - but over to the experts.
