1990 accord keeps frying alternators
 

INFO:
1990 HONDA ACCORD
4CYL.
AUTOMATIC TRANSMISSION

Hello forum! Just wanted to ask for some help to find out why my 1990 accord keeps frying alternators. for background, the first one lasted about a year, the second one 3 miles and the third about 20 minutes of idling. I cant believe all these could be bad.

Being suspicious, I disconnected the wiring harness from the Electronic Load Detector and there was no short among the 3 terminals on the ELD itself. However, at the wiring harness which connects to the ELD, the BLACK/YELLOW wire is shorted to the ground (BLACK) wire. so I referred to a Haynes manual and found that the black/yellow wire can be traced back to the following components:

BYPASS SOLENOID
EMISSION CONTROL BOX
ENGINE MOUNT CONTROL UNIT
ALTERNATOR
INTAKE AIR CONTROL SOLENOID

I disconnected the emission control box and the alternator to see if the short would go away and it didn't. I didn't test the other 3 because I cant find them.

Now what I want to ask is:
1) can a short on this wire or one of these components cause my alternator to fail?

2) Could someone please tell me the locations of the bypass solenoid, engine mount control unit, and intake air solenoid? I want to disconnect these components and recheck for a short at these as well.

Thank you all for your help in advance!

1. First check the amperage of Fuse No. 2 in the under-dash fuse box, it should only be 15A. If a higher amperage fuse was used instead, you risk the fuse not providing the intended protection and other components getting damaged when there is a short, etc.

2. That fuse and the Blk/Yel (IG) wire supplies the ignition input that turns on the alternator/regulator assembly.

3. The regulator in the alternator is probably what is getting damaged.

4. What trim level is your Accord? Not all models have the bypass solenoid and/or the Intake Air Control Solenoid Valve.

5. The Engine Mount Control Solenoid Valve is located at the center rear of the engine compartment (firewall).

Thanks Red Bull, I'll check the fuse out. Also my trim level is an X. Lastly the engine mount control solenoid it must be the one with the vacuum hose connected to both the intake manifold and the engine mount in the rear correct?

Sorry for the Misprint
the trim level is an e x

The EX does not have a bypass solenoid.

I will post photos of the components later today, I have things to take of this morning.

Thanks Red Bull and I'll let you know what I find.

Red Bull just to give you an update there is a 15 amp fuse at the number 2 spot. I also checked under the hood and found the intake air control solenoid and the engine mount control unit and disconnected both and still had the short on the black yellow wire and the ground wire.

I will take a look at the circuit diagrams then to see if there are other areas to check.

For informational purposes to other readers, attached are the photos for engine control mount solenoid valve and intake air control solenoid valve.

Thanks for doing that.Meanwhile I'm going to stop by The junkyard tomorrow and test the connections on an Accord at the junkyard and see if I get the same readings. If I do, I'm going to clip that harness away and check the wires behind it see if the short is still there. if it's gone then I'm going to suspect the actual wire harness itself that clips into the ELD.

Okay, went to the junkyard and tested about five Accords. Three of them were shorted out at the ELD harness and the other two were not. Of the three that were shorted I clipped the harness from the wires and the wires were shorted as well. And I clipped the wires from the harnesses on the ones that weren't shorted and they did not have on a short on the wires. Now I'm almost thinking that these two wires are supposed to be shorted.

Ok today I tested the battery and it turned out fine. Also, I disconnected the harness from the alternator, the green one, and checked the black/yellow wire for a short to the power steering pump bracket Brown and it shorted out to 64 ohms. I disconnected the brown harness that rests on the passenger side shock Tower and the short at the alternator went away. However the short is still there at the ELD harness and the harness leading into the firewall inside the car. I've narrowed short to being somewhere on the inside of the car.
I checked with the Honda dealership they couldn't give me a straight answer as to whether or not this short should be on this wire. So if anyone knows if this short should be here for sure and could let me know that would be awesome. Also, if there is a short on this black yellow wire that goes to the alternator will it fry it?. If not what are some common causes of frying and alternator on a 90 accord?

Today I connected my test light to the positive terminal of the battery and probed the black/yellow wire in the green harness of the alternator. Every time I touch it, it lights up letting me know that it is grounded. Also, when I initially touch it I hear something click I'm the underhood fuse block. It only clicks maybe the first 2 times I touch the light to the wire and it stops if I keep testing it and the fuse block only clicks again only after waiting about 45 seconds to a minute. Again I will say that I don't know if this black/yellow wire is supposed to be grounded or not.

also, could my eld be bad without triggering the check engine light? If so, how can I test it to be sure?

That blk/yel wire powers a lot of items that normally have a ground available. Your volt meter or test light test for ground may be show a ground, but the wire isn't shorted. If you had a dead short to ground, that 15 amp fuse would blow. The 64 ohms you are reading is likely the resistance through the different components on that circuit.

I'm using a 93 non-US shop manual, so I want to verify the wire colors before giving suggestions. The alternator looks to have a red/wht, blk/yel, wht/blu, and wht/red wire. Is this the same wire colors as your 90 accord?

I have:
Black wire/solid yellow stripe
White wire/solid red stripe
White wire/solid blue stripe
White wire/solid green stripe.
These 4 wires feed into the green harness that plugs into the voltage regulator inside the alternator. There is one more thicker white wire with a solid red stripe that attaches to the other terminal on the alternator and runs directly to the 80 amp fuse in the underhood fuse box. It's covered with black insulation the total length of it BTW.

I'd recommend using a volt meter to test the wires to the voltage regulator with the engine running and everything plugged in. You will have to back-probe each wire. A t-pin is commonly used or a thin piece of metal also can work.

The blk/yel, wht/grn, and the wht/blu wire should all have 12V.

The thicker wht/red wire should be the alternator output that charges the battery.

I'll have to figure out what the thin wht/red wire from the engine computer should read.

Just asking, what type of reading besides 12V would indicate one or more of these wires could be the culprit(s ) as far as damaging my alternator?