Good evening folks. Working on the old 1989 LX accord again.

Car drives fine when jumped, but battery has been going flat after a short time not driving.

I will give a short history if it helps: When I first obtained this car about two years ago, there was a parasitic drain already. I did the standard ammeter test and found that the problem circuit was the hazard lights, so I just pulled that fuse and this problem has not come up again until now. About a year ago, a coolant hose above the alternator leaked and shorted out the main alternator wire and blew a fuse. I replaced the fuse and alternator after that, but the battery light has been sporadically on while driving ever since, even when there is good charging voltage. I have actually replaced the alternator in the car three times total since then, as the reman ones seem to die often. The same random battery light remains. Last replacement was about three months ago, and things have been running ok since then. Currently alternator gives good 14+ volts charging.

Now for troubleshooting the drain, I disconnected the (likely well worn by now) battery and ran the test using the battery from another car which was healthy. With doors closed, Key off, all lights/etc off, I started reading 3.8A drain, which over time slowly lowered on its own to ~3.5A, clearly this is a huge short. I had someone monitor the meter and pulled each fuse on the driver side inside and the passenger side engine bay blocks. The only one which changed anything significantly was the 'Battery' one under 'Main Fuse' - current dropped to zero, but obviously this does not give any useful information except that maybe the problem is not with the starter / alternator. (I manually checked these too by removing the main post wires - they were not the cause of the drain) There was no obvious damage / degradation of insulation on the positive / negative cables, which was the last thing I could think to check offhand.

Are there any other electrical connections on these cars which do not go through the fuse block to look at? Any other possibilities?

Thanks much!

 

You said you unplugged the main post on the alternator. Try unplugging the other electrical connector to the alternator.

 

Well, thank you! Quick diagnosis. It was the alternator spade plug. This car has gone through so many alternators, I don't know if they are all crap or if there is something seriously wrong with the charging system.

Thanks for the suggestion and I am glad that the problem is found now.