97 4.6..battery came on 2 days ago but the truck still starts.. going to clean up the terminals a little today as they are nasty looking just wondering if this could be an early sign of an alternator problem? anyone seen this before, whats the troubleshooting procedure.

Also I replaced the egr vlv and cleaned the throttle body.. truck runs fine but the friggin check engine light is still on.. do you need one of those code readers to reset it or will it reset itself if I've fixed the problem?

1 more thing, the heater does not get hot at all but it does blow air and the A/C works..so I think it's just the heater core, I am thinking of replacing it, anyone have any tips/lessons learned from doing this?

Thanks

 

The codes will clear when you disconnect your battery to clean the terminals. If you still have a battery light after terminal cleaning... suspect the alternator.

 

Before you clear the codes you need to read them and see what they are. It MIGHT be related to no heat - where does your temperature gauge normally read?

 

Thanks, the codes were PO104 which have now cleared after I removed the batt. cables and cleaned them up. The truck restarted with no problems but the battery light is still on. How can I be sure it's the alternator?

 

P0104 is a MAF issue - clean it and make sure it's securely plugged in.

Take the truck over to Autozone or another parts store and get the battery and alternator tested.

 

Check the alternator field fuse, #11 in the underhood box, clean the battery posts but have both battery and alternator checked.

 

i got the same thing but mine flickers on and off...not like its reading a code...like its a strobe light...come on like...every 3-4months..if it aint broke dont fix it

 

The brushes are bouncing or almost worn out - your alternator is on its last legs.

 

just put it in. like 5 months ago. they ran test and all came out AOK

 

who installed the alternator? possible damaged wire during removal/installation? doesnt seem right. only problem with the saying, if it's not broke, dont fix it...in your case, it could leave you stranded somewhere.

 

To get to the bottom of the charge issue, use a voltmeter across the battery terms.
Just after starting, the voltage should raise to at least 15.5 +/- and taper down in a few minutes to about 14 volts as the battery recovers it's charge.
If you see this happeing, then the lamp issue is due to some other reason.
The alternator function and control are good otherwise.
A lamp only at higher rpm is very often the alternator brushes are worn and/or the comutator is rough such that the brushes can't stay seated.
Good luck.

 

That's EXACTLY what happened to mine last year.

 

check your body and engine grounds as well

 

So if I start my truck and let it run for about 2 minutes then remove the positive battery cable the truck should stay running correct?

If it immediately stalls out then my alternator is bad is this correct?

 

You don't have to pull the cable - just put a DC voltmeter across the terminals with it idling, MINIMUM voltage should be 13.8.