Alternator issues

[yols]

The alternator in my tj is not charging my battery. When I start the car the battery level is between 9 and 14.5 on the gauge. After driving for a few minutes, my check gauge light comes on and the battery gauge level drops to nothing.

When I detach the battery and reconnect again I have the same issue. I have paid for an electrocution to come out and says that alternator is run through the computer

After running power through the alternator it began to charge. He also tried to see if there were any engine codes and he couldn't communicate with the computer

Any one have any help at all with this problem. Driving me crazy

[Doctor W]

Try the ignition key on/off X 3 thing to see if YOU can get any codes up........his scanner may have been unsuitable.

Your Jeep's voltage and amperage output is controlled by the PCM (the "computer").....they're pretty reliable.......not sure if yours has a battery Temp Sensor under battery or not, but if they go then the PCM cuts back power.

Check that all connections at battery, alternator etc are clean and tight.......both power supply and the earth returns!

Have you got a multimeter to hook up to battery and start car -not drive anywhere- just run engine for a while -say 5 mins- and see what's actually happening.

Difficult to diagnose remotely but we'll have a go!

[yols]

No. 12; engine light flashed 3 times, no. 25; engine light flashed 7 times, no. 55; engine light flashed 10 times

No idea what this means. Is ther a way to find out

[Doctor W]

No. 12; engine light flashed 3 times, no. 25; engine light flashed 7 times, no. 55; engine light flashed 10 times

No idea what this means. Is ther a way to find out

OK,

12 = Battery power to PCM was disconnected /dropped down to minimum

25= Idle Air Control motor or circuit has a short or open circuit

55= End of test procedure

I'm not sure what you mean by the 3 flashes etc except that maybe it was 1 flash, pause 2 flashes = 1+2=12 etc and you just miscounted, dunno.

But if 12, 25 and 55 came up on your speedo in numbers that's what the codes are.

So you've got a problem in your Idle Air Control (IAC).....now you know where to start to look.......maybe the step motor's a dud or dirt????? on connections to it?

Maybe it's a short causing power in control cicuits power Approx. 5 V) from PCM to drop right down?......PCM is reducing power to avert catastrophy (short = heat = fire???)dunno.....

Have a GOOD look around everything to do with IAC and its connections, power AND earths! ....for a start.

Good Luck!

[Doctor W]

I worked out how you miscounted!

your 3 flashes = 1 flash, pause 2 flashes = 12

your 7 "" = 2 "" pause 5 '' " = 25

your 10 "" = 5 "" "" "" 5 " "" = 55


;)

[yols]

Doctor W... your good, your really good. A place to start is always better then none. since i have no idea, should i share this info with my auto electrician. Is the IAC the plug that goes into my air flow meter???? i will say it hasnt been idling all that great.

But will this solve my alternator not charging the car i wonder???

[Doctor W]

Doctor W... your good, your really good. A place to start is always better then none. since i have no idea, should i share this info with my auto electrician. Is the IAC the plug that goes into my air flow meter???? i will say it hasnt been idling all that great.

But will this solve my alternator not charging the car i wonder???

The IAC is NOT on the MAF (airflow meter) it's on the air throttle/butterfly, just above the intake manifold......it's the thing on the REAR of the air throttle ....[on the LHS is your MAP sensor]........the IAC is a step motor that drives a tapered screw valve that constantly adjusts the amount of air bypassing the throttle when it's shut, thus allowing the engine to idle at a constant preprogrammed speed no matter what load is on the engine, e.g. A/C on, cold start, high alternator load etc.

First off check the connections at the IAC - clean and tight , Electronic Contact Cleaner spray is good for this.

Maybe remove the IAC and check for clean passages - use Carby/EFI throttle spray cleaner.

Jeeps are really pretty simple machines and it's much more likely that your problem is a dirty/bad elecrical connection than an electronic failure - the PCM etc is pretty reliable, sensors can go bad sometimes and things like the IAC but most of the time it's usually dodgy connections.

[yols]

Hmm ok will look into that tonight. After going for a drive I also got code 47 which is a charging problem I think hence my battery going flat on me

[Doctor W]

Hmm ok will look into that tonight. After going for a drive I also got code 47 which is a charging problem I think hence my battery going flat on me

yeah....

47 = battery voltage too low for too long.

HAve you checked the actual battery voltage with a multimeter at rest and running at different revs???? Should be 12.6 at rest, 13.8 2 idle, max 14.6 at revs

Battery may be bad OR alternator may be bad -check Max output with an Inductive Clamp Ammeter, if you've got one handy- or know someone who does - TJ's should put out at least 80 Amps from memory with Std duty Alternator

[yols]

yeah....

47 = battery voltage too low for too long.

HAve you checked the actual battery voltage with a multimeter at rest and running at different revs???? Should be 12.6 at rest, 13.8 2 idle, max 14.6 at revs

Battery may be bad OR alternator may be bad -check Max output with an Inductive Clamp Ammeter, if you've got one handy- or know someone who does - TJ's should put out at least 80 Amps from memory with Std duty Alternator

Had a mate check it with an muti and it was reading low. When an auto electrician looked at it he said the alternator wasn't getting any power so it wasn't charging the battery.

Once he ran power through it the batter gauge went up to 14 on my dash. Bit bedazzled how it works. Maybe a new alternator will solve my problems

Could this be a faulty computer???

[Doctor W]

I found this great posting:

http://jeephorizons.com/phpbb/viewtopic.php?t=2719

Probably should be a useful sticky.

[yols]

thanks for all your help doctor W. after everything we change the alternator and gave the plug a very good clean out and it is back to normal.

[cherrykee]

Yols I'd be finding whomever you bought the TJ from and giving them a absolute kicking, i have just been trolling thru various posts and see that you have been having a rough trot with the vehicle, i know how annoying that can be i just shelled out $500 for a reco steering box yesterday...