Is it my alternator?

[revbeard]

Hey gang. I'm completely in over my head on the electrical with this 94 fj80. Previous owner installed deep cycle battery system with relay switch to power Engel fridge. He told me a previous battery had caused some electrical issues but it had been straightened out. Everything seemed fine. All buttons/functions worked (besides stereo, which had a blown fuse in the back).

Yesterday I ran an errand and had my car parked 45 minutes. I came back to a classic starter clicking sound. Truck that wouldn't start. I jump started it, and drove off, but then I noticed something new: when I decelerated, lots of indicator lights came on when I stopped at stoplights. Battery light, brake light, A/T light, engine oil light. When I accelerated, indicator lights would disappear, truck seemed back to normal.

Get home, same story. Difficult start. Jump started it again, let it idle in driveway for 5 minutes. Started to move it, and the truck just died.

Worried about jumpstarting it again, but I need to move it. Do I need an alternator?

 

[Kaninja]

Do you have a multimeter? At idle what voltage are you seeing at the battery?

 

[LandCruisinMy93]

Disconnect the secondary battery and jump
Start the rig with all the accessories and headlights turned off. Then while it's running remove the negative battery cable from The main battery. If the vehicle dies then it's more than likely your alternator. The other thing that should be asked is if your rig idles at the normal rpms? Lastly, if you can get a few good whacks on the alternator case with a block of wood or deadblow hammer while it's running that might cure it for a bit.

 

[revbeard]

Gonna go with the multimeter approach before getting out the hammer. As I understand it when I do a reading I should have a 12.6 V battery read until ignition, when it jumps into the 14s if the alternator is functioning properly.

Another part of my question is whether it is safe to jump the car without disconnecting 2nd battery. Can I do damage to the deep cell? Have I already damaged it? I assumed that relay switch would isolate the jump to the ignition battery.

 

[TomOsborne]

Sounds familiar. I had an issue that popped up with several weeks in between of normal running. Got to parking lot- dead. Got a jump fired up with vigor after sitting on cables for just a minute. Played with fusible link all the bells and whistels came on (dash). Finally pulled the alternator after it required the 3rd jump. This time it was cooked. Multimeter at 11 and change after ignition. Tested all leads from the battery to the junction box south of the fusible link first with the car not running. Bought a new alternator but now cant seem to get the damn thing in (hence a new thread I posted).

 

[2NDFZJ80]

Same experience when taking my kids out to the desert last weekend. Parked it to do some shooting but it wouldn't start. The battery is only a month old. Luckily someone drove by to give us a jump.

During the drive home the gauges went crazy and the red light was lit up on the battery indicator. Research points to alternator. Replaced the alternator and all is good.

 

[Shrubmaster]

I'm having the same issue, replaced battery and alternator, still not fixed. Needs a jump to start, dies after driving for five minutes.

 

[revbeard]

So

Sounds familiar. I had an issue that popped up with several weeks in between of normal running. Got to parking lot- dead. Got a jump fired up with vigor after sitting on cables for just a minute. Played with fusible link all the bells and whistels came on (dash). Finally pulled the alternator after it required the 3rd jump. This time it was cooked. Multimeter at 11 and change after ignition. Tested all leads from the battery to the junction box south of the fusible link first with the car not running. Bought a new alternator but now cant seem to get the damn thing in (hence a new thread I posted).

Why can't you get the alternator in? Can you link to your thread? Thanks and good luck!

 

[revbeard]

I'm having the same issue, replaced battery and alternator, still not fixed. Needs a jump to start, dies after driving for five minutes.

Weird. I'm afraid I'll replace the alternator and it won't fix the real problem. Have you had a professional look at it? (assuming you are just a hobby guy like me)

 

[LandCruisinMy93]

The reason I say to disconnect the second battery is so that the system doesn't try and feed off that battery once you disconnect the negative to the main battery. Disconnecting the main battery is a quick check to see if it's the alternator. Knocking on it with a hammer or piece of wood or something can knock brushes loose if they were stuck giving you a working alternator if not just temporarily. Hitting it comes after testing not before. And it's a test anyone can perform anywhere without a multimeter.

 

[revbeard]

It was the alternator. Back to cruising the land. Thanks y'all.

 

[CJF]

Thanks for posting the resolution. Too many people don't do that.