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1996 Bronco XLT 351W/ZF5, 1996 F150 XLT 351W/E4OD D44 Leaf Sprung SAS
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Discussion Starter #1
New alt, now belt squeals sometimes

My 1996 F150 with the stock 95A 3G is showing the battery gauge dropping while I'm at idle with the headlights on. Anything above idle and its right in the middle of 'normal'. Sometimes it goes higher while I'm on the highway. Anyhow....
Yesterday I found a 130A direct bolt-on from a fullsize van. I swapped it out, and when I started the truck, I got a squeal from the belt, and the battery gauge was way down, below the N in normal. I shut the truck off to check and make double sure that the belt was on right, because the old alt never did this. All appeared well, so I turned it back on. It squealed for a minute, then it stopped, and the battery gauge was back mid-normal.
So I started turning on lights, fan, etc, and it started squealing again, gauge way low. I shut off all the lights, fan, etc. and the squealing stopped and the gauge returned to normal.
Could it be that when I turn on all the accessories, the new alt is putting such a load on the (maybe) old serp belt that its starting to slip? Should I just replace the belt with a new one? I have no idea how old the current belt is.

I did a brief search (serpentine alternator belt squeal) and didn't find and answer.

thanks.
 

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yo 67

96 Bronco-F-Series Workshop Manual (PARTIAL)

Section 03-05: Drive Belts, Accessory
DIAGNOSIS AND TESTING
Symptom Chart — Accessory Drive Belt Diagnosis

•Excessive Noise/Belt Squeal
Seized accessory.
CHECK all accessories for free rotation and REPLACE accessory if necessary. REPLACE drive belt.

•Loose drive belt.
CHECK condition and tension of drive belt. REPLACE drive belt or ADJUST tension of manually tensioned drive belt as necessary.
CHECK that automatic drive belt tensioner is within the indicator marks. CHECK for correct drive belt length if drive belt tensioner is out of operating range.

READ MORE
=========

EDIT; added
Drive Belt Replacement
 

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YO,
"...Spray a LITTLE water on it. If the sqeak stops briefly, replace the belt. If not, use a mechanic's stethoscope to listen to each pulley with the engine idling. It should be obvious which one is squeaking. You can also watch the idler/tensioner pullies to see if they're wobbling. With the belt off, spin each by hand..."



This is by CLARKO; 3G Interchange Facts
Is the pulley from the Van; is it same size as the Bronco's pulley?

"...Pulleys: For pulleys, you can either re-use your old one, which sometimes you may need a very small washer to use as a spacer if it rubs in the 3G case at all, or you can get a different sized one. It all depends on your needs. A smaller pulley will spin the alternator faster at idle to create maximum output. A larger pulley will allow the engine to rev higher without driving the alternator to fast..." by Steve83
 

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1996 Bronco XLT 351W/ZF5, 1996 F150 XLT 351W/E4OD D44 Leaf Sprung SAS
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1,435 Posts
Discussion Starter #4
I went outside thinking that I would take the brand new, still in package serpentine belt out of the cab of my bronco w/5.0 and put it on the 5.8 in the F150. I ASSumed they would be the same. While I had the belt off, I spun every accessory, and they seemed to spin fine. I may have mentioned earlier that there was no squeal at all with the old alternator (and the 130A one didn't cause a squeal all the time, only under high electrical load). Anyway, I found out that the 5.0 and 5.8 use different length belts, so I put the old 5.8 belt back on. I'll swing by NAPA tomorrow and get a new one for the 5.8.

But I did go online just to check. Seems that any 1996 F150 with the 5.0 will have a 99.62" circumfrence belt, but a 1996 F150 with the 5.8 will have either a 93.98" or 102.57" belt. Looks like I'll need to specify the longer one, since the 99" 5.0 belt was just a little short.

I didn't measure the pulley diameter, but at some point I did lay the two alternators side by side to note the case size difference between the 95A and the 130A. I didn't notice that the pulleys were different. I'll check those just to be sure.
 

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1996 Bronco XLT 351W/ZF5, 1996 F150 XLT 351W/E4OD D44 Leaf Sprung SAS
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Discussion Starter #5
So, I installed a new belt from Napa (the expensive one marked Made in the USA), and a new tensioner. Truck idling smoothly with high beams on, fan on high, gauge right in the middle of 'Normal', no squeal. I'm satisfied. Sad though that the belt cost more than the alternator.

Turns out that the van alt did have a smaller pulley. It is 2.5" across the face VS 2.75 for the truck alt. Is this a bad thing? I know it will only take 30 minutes total to remove the alt and swap pulleys, but am I doing anything wrong leaving the slightly smaller pulley on there?
 

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