Belt squeals when electric fans turn on??? WTH

[Mrturner1]

Kindof a weird problem I'm having now. It happened yesterday and again today after I got done installing power steering parts.

So with the truck idling in PARK the idle rpm is about 750 and seems healthy, revs good and sounds like it's supposed to. I let it warm up to operating temp and then to test it out, I flipped the ON switch for the electric fans. The idle dropped to 450-500rpm, and in an effort to get the rpm back up I gave it a little gas (not revved, just a bump) and the belts squealed. Let off and it went back to 450-500 rpm and I bumped the gas a couple more times, same thing, loud belt squeal. Thought that was really weird because electric fans and belts don't touch at all or run off of each other. So I turned the fans back OFF, idle went back up to 750, and the belts were quiet when I bumped the gas and revved it hard.

This has me totally stumped, and I think it's the cause of yesterday's tuning issue and the studder I felt once while driving into town. I don't understand why the electric fans would make the belt squeak. I do understand the drop in rpm's when I turn the fans on to a point. I'm guessing here but the sudden draw of power that the fans require could cause the rpm to drop?

I'll post a few pics of my setup in case it helps. The alternator is a 140 amp, fairly new. I'm not 100% confident in the PO's wiring job but I've chased down most of his butcherings. Fans are dual Flexalite and draw 30 amps I believe.

[Mrturner1]

Pic

[indymachinist]

The fans are putting a significantly higher draw on your alternator. The fact that your idle drops 300rpm certainly shows there is a high alternator load. So then the alternator is harder to spin, causing the belt to slip.

Either you have a very high amp draw pair of fans, or maybe your alternator is getting weak? Poor grounds or power leads for the fans?

[geunther]

Wondering if the fan's draw cause more load on the alternator, and with the extra load comes the squeal?

[Mrturner1]

It seems like 140 amp should definitely cover everything to me but I could be wrong. I bought the alternator used from a guy here, so I guess it could be older than advertised.

[indymachinist]

Are the fans 30 amps each or total? We're the fans new?

[trac209]

From the pics it looks like your alt is Chrome. If the pulley is Chrome as well you could try a litte emery cloth to rough up the pulley where the belt touches,it may provide some extra grip so it stops squealing.

[Mrturner1]

Originally Posted by indymachinist

Are the fans 30 amps each or total? We're the fans new?

30 total

[Mrturner1]

Originally Posted by trac209

From the pics it looks like your alt is Chrome. If the pulley is Chrome as well you could try a litte emery cloth to rough up the pulley where the belt touches,it may provide some extra grip so it stops squealing.

Should the rpm drop so much though?

[trac209]

Originally Posted by Mrturner1

Should the rpm drop so much though?

No not really,is this drop measured with a reliable tach or just but how much it sounds like it's dropping? I would try running only one fan and see if the drop is the same. The fan should not draw so much that the engine drops so much.

[Chknlyps2]

I have a total of 400 watts of off road lights on my square body 4x4, that is roughly 30 amps and when I have them all on my rpm might drop 50 at most.

Do you have a spare in dash amp gauge? borrow one if you don't and wire it temporarily in line on the hot wire feeding the fans to verify they are drawing 30 amps.

[Mrturner1]

Originally Posted by trac209

No not really,is this drop measured with a reliable tach or just but how much it sounds like it's dropping? I would try running only one fan and see if the drop is the same. The fan should not draw so much that the engine drops so much.

Brand new autometer

[hamjet]

Do you have the fans going through a relay first? That will stop it...

[Mrturner1]

Actual draw is 14-22 amps, just checked to be sure. Everything is wired up really nice too. I'm starting to wonder about the actual alternator wiring. Here's a picture of the harness I'm assuming the PO made himself

[Mrturner1]

Pic

[indymachinist]

That alt wiring looks... not all that great. What gauge wire is coming from the main alt. post?

[Mrturner1]

Originally Posted by hamjet

Do you have the fans going through a relay first? That will stop it...

By relay do you mean the black box that ALL the wires ran to with the kit, that has the variable temp knob on it?

Sorry first timer here lol

[Mrturner1]

Originally Posted by indymachinist

That alt wiring looks... not all that great. What gauge wire is coming from the main alt. post?

What's with the loop made with the wire nut? Why would he make it that way?

[indymachinist]

It's hard to see what is going on completely in the pic but wire nuts should not be used on automotive wiring at all in my opinion so that makes me skeptical of all the rest.

[Mrturner1]

Is there an aftermarket alternator wiring harness? Maybe wiring harness isn't the technical name lol but does one exist?

[biketopia]

holy fire waiting to happen. fix that alternator hook up and use good glean connections, not wire nuts. Like the others said check your grounds and double check all that alternator wiring and battery connections. Might not hurt to pull the alt and run it up to a parts store and have it tested out for piece of mind. Years ago I got 4 bad alternators for my old 93 K5, right out of the box from the local parts store.

[GASoline71]

Wire nuts are for houses... even crimp terminals would be better than that.

Gary

[dazza]

maybe move the wires a bit to get a better picture of how they're connected, it's too difficult to see, or draw it out and post it.

[BossHogg69]

Originally Posted by Mrturner1

Actual draw is 14-22 amps, just checked to be sure. Everything is wired up really nice too. I'm starting to wonder about the actual alternator wiring. Here's a picture of the harness I'm assuming the PO made himself

Obviously you have some wiring issues that may be contributing to your issue, but I'm using a very similar set of Derale fans, and that amp draw was what EACH fan pulled on my setup - but it wasn't printed that way in the specs. I know that's what they list, but you may want to confirm by calling Flex-a-Lite to make sure. My big block idled at 1100 rpm, and when the fans kicked on it would go down to 900. I'm running a Powermaster 105 amp alternator.

[elf w/capital T]

how did you mount that fan shroud??