[GMAs]

Way back when we discussed this on the other site... I spent 7 long articles on how to check the system and how it worked... and showed that it worked well... some of the oldies might remember... but, a good mechanic should be able to go to the area of the problem...

If as you say you pulled the fuses and checked them and they were OK... then the system worked for a while... I would have done it again.. except that this time I would have cleaned up the fuse holders.. hint...hint... which have a tendency to get tarnished and can cause you not to get any voltage back to the alternators to make them take off....

Yep that is a problem area... best to take the fuses and throw them away.. put new in because sometimes the lead connection inside gets bad too... check the wires on the fuse blocks... check the screws for rust and corrosion... dont just spray it with magic cleaner... remove the parts and clean with something like a pad...

Now if the alternators were not taking off.. it means that no voltage from the system is getting back to them... here their are only a couple of things... as they are related to the field...

The main master to the ckt breaker... to the field switch on the dash... thru the overvoltage limiters...thru the fuses thru the connectors on the regulator plugs... to the regulators then on to the fields themselves...

The return ckt is....

from the alternator thru the cable to the blocking diodes to the master to the battery...

so what part is not working...

First start with the alternators themselves... look for a mechanical problem.. they have to turn... so the coupler is first to check... then the next thing is the brushes.. for the field... these can be tested with a meter... then the wires that go to the alternator.. look for broken wires at terminals...

At the other end of the plane.... the overvoltage regulator is only going to trip out the relay inside it when the voltage gets too high... ya the contacts could be dirty... and as we have said before.. the planes that goe way up their... have a world all their own that they go thru... with moisture and pressures being the bad guy....

The field switch is another problem area.. with P and T planes... again because of the pressure... but, these can be tested... I again wrote an article after talking to the cessna person I found who used to design the systems.. and test them... he had lots of helpful info.. that I passed along... on how they trouble shot the system... just using a volt meter...

But, when everyone keeps putting more on the system and adding instruments that can present problems to the system... it sure isn't going to work the same as it was designed....

So that leaves the stuff out in the engine compartment.. the regulators and the diode/relay board... with the fuse holders and connectors being the biggest problems... (fuse holder being the biggest problem...) as it will corrode..... and it only has 24 volts at 5 amps max that it has to handle... that being 100% output from the system.... from their the amps go down to about 1 each... so if their is any resistance... the sense would say no voltage but, the alternator is not getting its field voltage... kinda thing...

First stop.. the shop manual...

Second stop... voltage checks... around the system...

Third stop.. back here with some data that we can make a determination about... (look at the fuse blocks... hint hint...)

Forth is not to go fiddling in the system (and that means put the adjusting screwdriver back in your pocket... 99% of the time its not the regulators... its other parts of the system that they can't handle...

So you need voltage to make it happen... sort of thing... if you are not getting voltage from the buss... then your not going to generate any from the alternators... kinda thing... so go out to the plane and get the mechanic to take readings... without the enignes runing... (again you can shoot the system without having the engines on... till the last Part... mechanical problems)

Let us know how you do... I have been asked to hold a meeting out here in the west for just that thing... electrical charging system... and I think we need to have one so that you all can get caught up on the right way to trouble shoot it... after all Harry Bowdish is going to be hairless if he gets into a bind too... and then his wife will have to send him to the hair club for men... ever notice how they have good looking young gals in their adds... with these old bald men... smile... GMAs