OR75 Posted June 10, 2020 Report Share Posted June 10, 2020 The voltage starts blinking pretty much right after I turn the master switch on. Is it an indication that the battery is getting weak ? Concord 35XC sealed 12V battery on a battery minder. About 4-5 years old . the starter showed a couple of hesitations in the past few starts. Quote Link to comment Share on other sites More sharing options...
carusoam Posted June 10, 2020 Report Share Posted June 10, 2020 What voltage is able to blink? If we are discussing the voltage light in the annunciator panel... Go directly to Clarence’s post below... It’s an important sign that your alternator isn’t turning enough rpm to keep up... Usual cause... the engine hasn’t started yet... When does it stop flashing? Often when a certain rpm is achieved... which is faster than usual taxi speed... For more info regarding the instruments in your plane... there will be a paragraph covering each instrument with their specific details... That paragraph can be found in the POH for your plane... Some parts of the annunciator panel can be adjusted... Use caution, the annunciator may have two skills... High voltage steady light? Low voltage flashing light? You may want to check your voltage with a meter... there are many portable digital devices discussed around here somewhere... Some expensive devices don’t handle high voltage very well... PP thoughts only, not a mechanic... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Guest Posted June 10, 2020 Report Share Posted June 10, 2020 A flashing light indicates an under voltage. It may be a low battery, or a poor connection causing an under voltage indication. Clarence Quote Link to comment Share on other sites More sharing options...
carusoam Posted June 10, 2020 Report Share Posted June 10, 2020 Clarence is technically the best! Best technical knowledge Best technical documentation Best at sharing the details Thank you Clarence! Best regards, -a- Quote Link to comment Share on other sites More sharing options...
OR75 Posted June 11, 2020 Author Report Share Posted June 11, 2020 it flashes when i turn the master and before the engine starts Once the engine starts, even at low rpm, no flashing and the voltage on the bus is 14.0V My question is: is it normal for the Low voltage annunciator to blink as soon as the master is turned on ? or does it indicate my battery is weakening ? Quote Link to comment Share on other sites More sharing options...
EricJ Posted June 11, 2020 Report Share Posted June 11, 2020 Note that the test procedure that Clarence cited says to check after engine start. Before engine start it is not unusual to have a voltage warning, since it's primary purpose is to indicate alternator failure. Note that the light is supposed to come on at voltages below 12.4 to 12.6 volts. The battery will often not be able to supply that much to the bus unless the alternator is turning. Quote Link to comment Share on other sites More sharing options...
EricJ Posted June 11, 2020 Report Share Posted June 11, 2020 Just now, OR75 said: it flashes when i turn the master and before the engine starts Once the engine starts, even at low rpm, no flashing and the voltage on the bus is 14.0V My question is: is it normal for the Low voltage annunciator to blink as soon as the master is turned on ? or does it indicate my battery is weakening ? It is not unusual for the annunciator to come on before the engine starts. It's mostly indicating whether there is enough voltage to charge the battery. Quote Link to comment Share on other sites More sharing options...
bradp Posted June 11, 2020 Report Share Posted June 11, 2020 If I’ve had the radios running, checked lights pitot etc for any significant time, I’ll get an undervolt warning before the alternator comes on line. Quote Link to comment Share on other sites More sharing options...
testwest Posted June 16, 2020 Report Share Posted June 16, 2020 (edited) OK, we had this issue on 201JX. With the master switch and the radio master on, but no avionics on and no avionics fan (pull the circuit breaker for the fan), measure the voltage at the battery terminals, and then from the radio bus to a ground in the front of the airplane. The only loads should be the battery master relay and the radio master relay. The front voltage will be lower, but it should be only about .3 or .4 volts lower, due to unavoidable losses through the positive cable that comes forward from the battery to the starter solenoid and thence to the rest of the busses. If it is a lot lower, like more than a volt lower, check where the grounding cable from the negative post of the battery is bolted to the airframe. On ours, the loss was 1.25 volts. Upon removing the ground cable from the airframe (it attaches to the forward avionics shelf in our airplane) I found corrosion and primer between the cable and the structure. The hole on the right is where the battery ground attached. This view is looking downward on the aft left surface of the avionics shelf, and the tail of the airplane is towards the top of the photo. And here is the shelf after clean up. The grounding area was cleaned with a stainless steel bonding brush, then treated with Alodine 1132 from an Alodine pen. This was on both lower and upper surfaces. Also provisions for assured electrical bonding were made where the shelf attaches to the fuselage stringers, one on each side. This is visible under the cleco on the right side of this picture: The voltage drop going forward went from 1.25 volts to .3 volts with this change alone. No wonder 1JX was never a very energetic starter, even with a fully topped off battery. And of course everything was fine with the alternator on, just like the OP experienced. Edited June 16, 2020 by testwest Adding pictures and information 2 Quote Link to comment Share on other sites More sharing options...
carusoam Posted June 17, 2020 Report Share Posted June 17, 2020 Awesome details With pics, Norman! Thanks for sharing them... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
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