ALternator?

[fordy6]

1997 GMC 1500 pick-up diesel 4X4 6.5L turbo...... On the road the other night my battery light came on. My Tach also quit! I made it home and the next morning I started her up. The battery was pretty low but she turned over. I noticed a noise emminating from my alternator. It was shot! I replaced it but now it doesn't seem to be charging on the gauge and the battery light comes on at low RPM's. The Tach also ceases to work at low rpm's. I checked the belt and it seems fine. Now both batteriess are dead and I have them on a trickle charge. I plan on starting her up as soon as my batteries are replenished..............Any ideas why the new alternator only works at high revs'?
Mike

[a5150nut]

I would have the alternator checked. And clean all connections. Including ALL ground connections. There are some on the passenger side head that nead special attention. Check your battery cables for internal corrosion, swollen spots in the cable, acid around the ends. And be very sure the new alternator has the same size pully as the one that came off. Your alternator is also your tack sending unit. If the pully size changes so does your tack reading.

[fordy6]

Good thought a5150,
I did just that. I also checked all connections. I pulled the alternator once again but I didn't bench test it. It is brand new and not a re-ferb! After I reinstalled the alternator and reconnected the batteries it stiil would not read RPM's. I have to rev to at least 2,500 and the battery light would go out and the Tach would work. As soon as I ease off the accelerator the light comes back on and no RPM's reading! Think it's a faulty alternator? I suppose I can remove it again and take back to NAPA and ask them to bench test it. At least I would know that the part was okay.
Thanks,

Mike

[DmaxMaverick]

Welcome to the Forums, fordy6!

A bad alternator right out of the box is not unheard of. Realistically, it happens a lot more often than it should. If your connections and grounds are good, and it still isn't right, take it back. Chain store reman's are notorious for hit/miss quality, especially when it comes to alternators and starters. I, and many folks here, have found it it often a much better option to have your OEM alternators and starters rebuilt by a local shop, and most of the time, cheaper than the parts house replacements.

[fordy6]

It's a Delco Remy out of the box and was told that it was not a re-build...........but like you said it's not unheard of to get a bad one.
I'm a bit upset that it took the entie day to do this 20 min. job, and it's turned into a major headache and I'm still out of a truck for work tomorrow!
Thanks for you help and ideas a515 and DMAX.

[DmaxMaverick]

Unless you find a stash of NOS (new old stock), there should be no "new" Delco Remy alternators. The series your truck uses have been discontinued for many years. The Delco Remy cores are the best for reman's, but the reman is only as good as the components used and the rebuilder's QA.

[fordy6]

I didn't find a reman slip in the box, just a warranty slip.
I just find it strange that I was just driving along and my battery light came on and my Tach fluttered for a while then quit............like I said I managed to get it home and it was obvious to me that every thing was running off the battery. I started her up in the morning and my alternator was screaming. When I replaced the alternator I disconnected both batteries and checked my belt for cracks. I measured the pulley and they where identical.
I have faith in myself that I did it correctly but upon starting her up I had a bouncing tach and a battery light on the dash. My owners manual says to check gauges..............?
Only when I rev it up to 2,200 or so RPM's the light went out and the tach worked. I just went through the same procedure again thinking I forgot a wire or something but there is only one wire to the Alt. and a plug that looks in good shape.
I was sure that the alternator was my problem, but now I guess it's a little deeper than that.
Thanks for your help,
Mike

[rjwest]

VOLTMETER, On the Batteries, should be 13.8V minimum, check it with
headlights on, at least 13.5 , That way you will know if Alt or instruments.
If Low Voltage :
jumper cable from alt bracket to neg battery post to check for
'lost ' ground,

Also , ohm the big plus wire from the connector to battery ( unhooked at alternator ) should be very low resistence.

[fordy6]

I brought my pickup to a GMC qualified dealership today and it's staying overnight for obsevation! When I left three mechanics where scratching their heads.
They made a call to Tech help and their response was it's a bad cluster. My question is , is it a coincidence that my alternator bearings quit on me and all of a sudden there is a problem in my cluster?
They want $250.00 for the cluster $85.00 to install it and that might not be the problem!

They bipassed the tach and took a reading with a Tech 2 and it was reading at idol 500 rpm, but the battery wasn't charging. The tech book says to pull the alternator, unplug, turn on ignition and check brown wire still don't know the outcome from that.
I'm into this thing for over $250.00 so far and still no answer to my problem.
Tomorrow is another day, perhaps something will pop into someones head.
Thanks all for responding to this inquiry, I just hope it helps someone else up the road.
Mike

[sturgeon-phish]

Same symptoms happened to me a few months back. Local shop rebuilt the alternator for $65 and had it done in 30 minutes
Jim

[Warren96]

Do not take it to the dealer,take the new alternator back and tell them that it is bad.The dealer will keep throwing parts at it until you get disgusted or you are bankrupt! Most dont have the trained personal to service a diesel properly,they don't sell enough diesel's to justify the cost.

[rjwest]

Never Never Never Go To A Dealer!!!!!!!!!!!!!!!!

[fordy6]

Well the saga continues.........................My GMC has been in there shop for 9 days now and all that the tech guys can come up with was a bad cluster.
The mechanic stated that the guys on the Tech line are very seldom wrong. I just thought it was odd that my original alternator went bad and all of a sudden my cluster went bad also.
They wanted $250.00 for the cluster plus $80.00 per hour to reinstall! They sent it out to be rebuilt because they are required not to touch the odometer only the other gauges. The cluster came back rebuilt, now I have no idea if in fact it was the cluster that was kaput! The mechanic reinstalled the cluster (a grand total of 7 minutes). Still no Tach and the battery light remained on.
I told him to pull the replacement alternator and I would take it to NAPA to have the original and the replacment alternator bench tested. Ha ha, as I suspected the original was toast and the new one was very week. I was issued a new alternator got my core deposit from the original and bought a new belt. I brought it back to the Dealership and and it worked just fine.
I had a lengthy conversation with the Servise Manager about my cluster that was priobably okay when it was sent out and they agreed to wave that cost. Funny though yesterday the called me and said my cluster was in and to make an appointment to have it put in. I had to remind them that my truck was in their parking lot and had been for 9 days. Why would I need an appointment? .........Gees, these people haven't a clue. Won't be going back there again!
Thanks to all,
Mike :)

[fordy6]

Problem fixed..................Bad alternator out of the box. They waived the cost on rebuilding the cluster which I am just assuming they rebuilt. What I mean is, why would they try and fix a cluster of there is nothing wrong with it?!
Their tech told them the problem was in the cluster, had they pulled the new alternator and bench tested they would have found it was bad.........
Won't be back there in any hurry!
Thanks all,
Mike