Weird charging symptoms
 

Ok here goes. 1991 honda accord LX 2.2. 5 speed
New battery and new drive belt, replaced alternator with a know good unit.
At idle with full load (lights on, door open, heater fan on high) voltage climbs to around 14.7
If i rev the engine the voltage drops to less than 12.5 (battery voltage is 12.7 with engine off)
cleaned and chaecked all cable, check all fuses, have batt voltage at black yellow wire at alternator.
checked visually and with meter all fuses under hood and inside car.
Battery/charge light does NOT come on at all even at start up/diagnostic check. Grounding blue white wire at alternator does not light the lamp either.
Followed the poorly written trouble shooting guide in Haynes manual. It appears to be the "Intergrated control unit" above the kick panel. This appears to be the only USA mad part on the car.

RE: Weird charging symptoms
 

Are you haveing problems with the battery going dead? The ecu controls the alternator, it doesn't run full blast all the time.

RE: Weird charging symptoms
 

acts like a bad voltage regulator ..

have a shop do a charging system test .. I assume you DID NOT use a Honda alternator ??

RE: Weird charging symptoms
 

Yes the battery goes dead after driving for a while. the car will run if i shut it off the battery is dead and will not start until recharged. The replacement was a Nindenso (sp) alterantor out of another accord that was running, But had trans problems, nice to have friends. The puzzling thing is that little battery light does not come on. I plan on pulling the dash among other things today to check the bulb.
The ECU was mentioned, as a ford guy the ECU is the computer that controls the engine to me. I was refering to the control box above the fuse panel called and Integrated control unit in the manual. not the computer under the passenger side toe board.
As for charging test voltage is fine at idle, it is as rev's increase that the voltage drops.

RE: Weird charging symptoms
 

Latest update, and hour later.
Okay did some tests and found that the passive seat belt motors had a continiuos draw. I pulled those two fuses under the hood. now the car charges around 14.3 volts at idle, and the voltage doesn't drop as I rev the engine. Sucess ......Yeah right. If i load the alternator (turn on heater/ac fan or headlights) the voltage drops again. Almost like the damn ICU or load detecter is wired backwards. I guess it still could be the used alternator. I grounded the blue white wire from the alt and still no battery light, gonna pull the dash next and check the bulb.
Any where else to turn before i blow $100 bucks on a rebuilt honda alt??

RE: Weird charging symptoms
 

next update. The dash bulb good.. so problem is elsewhere right? I guess signal is not getting from alt to ICU to bulb and back...Likely place to check? Or just start probing wires?
Any help at all at this point would be most appreciated. Don't mind blowing the $100 on alt if it will fix problem. but at this point everything seems to point elsewhere than the ALT.

RE: Weird charging symptoms
 

Well still looking. no battery voltage at white/green wire on alt.

RE: Weird charging symptoms
 

can't trace white/green wire. relay mentioned in repair manual i can't find. Engine compartment very tite for big guy like me.

RE: Weird charging symptoms
 

I'd have a charging system test done as Desert mentioned. Also if that manual is a pain the rear you can download a service manual for free.

http://hondatech.info/downloads/Auto/Manuals/Accord/

RE: Weird charging symptoms
 

i tested the charging system. hence the post with voltages mentioned.
trouble shooting steps lead me to white/green wire not having bat voltage (engerizez alt?)
Okay took the alt out and went to the auto store. Put in on the machine. It is fine!! full voltage and amp load. Last test is to disconnect the sensor wire white orange? If the system charges with out this wire??
So back to wiring and or sensors load dector what not. Load center is integrated into fuse box, under hood?? is it replaceable from underneath? Does the car have to go to honda for service? What are my options at this point?

RE: Weird charging symptoms
 

You mention being a Ford guy when Chio said the ECU controls the alternator. Yes, that's the Engine Control Unit. It has a control wire to the alternator & it can shut down the alternator by grounding that wire.

There's an elecrical load detector (ELD) built into the fuse box. When the battery voltage is good, and the ELD indicates little or no electrical load, the ECU will signal the alternator to shut down.

But... if that signal wire has its insulation rubbed off, & shorting to ground, THAT will also tell the alternator to shut down. I don't have a '91 repair manual so I can't tell you what color wire that would be.

RE: Weird charging symptoms
 

the saga continues. I downloaded the manuals recommended above. after pouring over them i found that there are four things that control or affect the alternator output.
the regulator in the alternator
the ECL in the under hood fuse box
the Integrated Control Unit above the fuse box behind the drivers side kick panel
and finaly a small 4 wire relay located above the glove box on the right side of the car.
Well I pulled the relay and it tested bad. no ohms or continuity. took it to the auto parts store they had no listing at Advance or NAPA..local store called Bumper to Bumper had one on the shelf. Bingo everything is fine YAHOOOOOOOOOO!!!
Thanks for the help guys. I love forums.....

RE: Weird charging symptoms
 

Thanks for posting the fix. Glad your problem was solved!

I know this is an old thread but does Anyone have a clue what the relay is called this guy replaced? I'm having the same symptoms with my 94

Check that alternator control wire mentioned in the earlier posts in the thread.

Just because his was a bad relay, you should go through the process of ruling out the more common reasons because it's likely yours is not exactly the same failure.

91 & 94 are different generations of Accord, so your alternator control circuit might not even be the same as his.