Fans roaring like a ticked off bear

[OBSandaNNBS]

Hey y'all,

I did peruse for old threads, but didn't get a straight up answer.

It's my first summer with the truck, so I'm not sure if this is abnormal. 156k on the 5.3.

When it's hot (85+) out, the fans click over to high. That's expected, but they are LOUD. Like hear them going at 70 on the freeway loud.This is only with AC on. Turn it off and they don't click over to high.

I know they are loud, but this seems off. I do have the J5L rpo code.

Secondly, with low engine speed, I can watch my dummy gauge drop from ~14.5 to ~13.5 in about 10 seconds. Eventually makes its way back up.

So my question is, is that normal?

I also have a slight rpm surge on 2-1 downshift ever since my throttle body wire debacle. The fan surges with it!

Thanks!

 

[swathdiver]

Fan noise is normal with both powered on high.

Voltage fluctuation is because the BCM controls the output of the alternator. Look up the terms Electronic Power Management and Regulated Voltage Control.

 

[Joseph Garcia]

First, a fluctuating voltage on your dash may simply be the truck's battery preservation mechanism working not to overcharge your battery, when it is full of charge.

I don't hear my fans at 70 mph, though my music is usually playing rather loud.

 

[Doubeleive]

Hey y'all,

I did peruse for old threads, but didn't get a straight up answer.

It's my first summer with the truck, so I'm not sure if this is abnormal. 156k on the 5.3.

When it's hot (85+) out, the fans click over to high. That's expected, but they are LOUD. Like hear them going at 70 on the freeway loud.This is only with AC on. Turn it off and they don't click over to high.

I know they are loud, but this seems off. I do have the J5L rpo code.

Secondly, with low engine speed, I can watch my dummy gauge drop from ~14.5 to ~13.5 in about 10 seconds. Eventually makes its way back up.

So my question is, is that normal?

I also have a slight rpm surge on 2-1 downshift ever since my throttle body wire debacle. The fan surges with it!

Thanks!

you must mean K5L, I upgraded mine to 700w 7/9 blade fans from a Hummer, they can be a little loud but you only hear it while parked and ac on or something and windows down or from outside the vehicle.
maybe you need to monitor the temperature with a scanner, it shouldn't be getting hot enough to make the fans kick on high speed at 70mph unless it's not cooling properly which could mean time for a new radiator.
as for the surge of fans during shift maybe to you need to check the wiring, battery connections, grounds....
"some" voltage fluctuation is normal with the RVC but it shouldn't be extreme.
how old is the battery?

 

[OBSandaNNBS]

Fan noise is normal with both powered on high.

Voltage fluctuation is because the BCM controls the output of the alternator. Look up the terms Electronic Power Management and Regulated Voltage Control.

Thanks for the reply!

As far as noise goes, I expected it to be loud but this is LOUD. Like louder than any vehicle I've heard. Is there a good way to determine if the fans are pulling too many amps? Is that possible to explain the noise?

I read the sticky about RVC, but was just alarmed at how fast the gauge dropped. Yeah just a dummy gauge, I could break out the scanner on the next hot day.

 

[OBSandaNNBS]

you must mean K5L, I upgraded mine to 700w 7/9 blade fans from a Hummer, they can be a little loud but you only hear it while parked and ac on or something and windows down or from outside the vehicle.
maybe you need to monitor the temperature with a scanner, it shouldn't be getting hot enough to make the fans kick on high speed at 70mph unless it's not cooling properly which could mean time for a new radiator.
as for the surge of fans during shift maybe to you need to check the wiring, battery connections, grounds....
"some" voltage fluctuation is normal with the RVC but it shouldn't be extreme.
how old is the battery?

Haha that's just my lis-dexia kicking in it's K5L.

When they are on, you can hear it regardless. I heard it from inside the house, on the freeway, windows up, idling, you name it.

I will monitor with my scanner on the next hot day.

The coolant is a touch low. Maybe a quart. Been on my list for a minute...got a replace those heater tees too.

At the hazard of sounding like an idiot, I don't know how old the battery is, it's older than my ownership. It's an AC Delco unit, how can I tell? No obvious markings like on a duralast.

What would you consider extreme voltage fluctuation?

 

[OBSandaNNBS]

First, a fluctuating voltage on your dash may simply be the truck's battery preservation mechanism working not to overcharge your battery, when it is full of charge.

I don't hear my fans at 70 mph, though my music is usually playing rather loud.

If memory serves, you've got a dual battery with a big 3 and a sound system? Bigger alternator?
Wait, do you play your music to drown out the fans?

 

[OBSandaNNBS]

you must mean K5L, I upgraded mine to 700w 7/9 blade fans from a Hummer, they can be a little loud but you only hear it while parked and ac on or something and windows down or from outside the vehicle.
maybe you need to monitor the temperature with a scanner, it shouldn't be getting hot enough to make the fans kick on high speed at 70mph unless it's not cooling properly which could mean time for a new radiator.
as for the surge of fans during shift maybe to you need to check the wiring, battery connections, grounds....
"some" voltage fluctuation is normal with the RVC but it shouldn't be extreme.
how old is the battery?

I'm not very good at finding threads, did you do a write up for the fan conversion? If not, are you happy with it?

I was under the impression from another thread that K5L is 700w motors. Is that correct? I have two 5 blade rimless fans. 2012 flex fuel if that matters.

 

[Doubeleive]

I'm not very good at finding threads, did you do a write up for the fan conversion? If not, are you happy with it?

I was under the impression from another thread that K5L is 700w motors. Is that correct? I have two 5 blade rimless fans. 2012 flex fuel if that matters.

Yes there are 5 blade 700w fans, i just went with the hummer shroud because it is easily verified to be 700w, out of all the gmt900 junkyard vehicles I have been thru not one has been K5L, yet you see a ton of them listed on ebay as K5L.......
besides the fact I bought brand new 700 motors for it....
in any case all fan shrouds fit the same 00-14, 700w use the same relays and wiring. so nothing really to "write-up"
if a person were to upgrade it's 100% plug-n-play
as for voltage fluctuation I can only speculate based on my own experience which is when the battery gets weak, the voltage gauge shows a lot more movement. A good fresh battery will show 14v (center) on the gauge more often than a weaker battery which may show less than center more often.
Voltage should be more solid no flickering headlights or erratic stuff going on. (such as the fans surging)
the gauge fluctuation is normal regardless, it's more of a matter of "how much".
you can do some easy testing of the battery by checking the voltage with a meter in the morning before the 1st start and see where it is sitting after resting overnight, then check what the voltage is running after it has sat idle for more than 2 minutes, because at first startup the alternator is automatically commanded to give increased voltage for the first minute and half or so.
then check the battery again after you have drove it for the day (engine off) and compare that to the morning resting voltage, if it is dropping more than a little bit overnight that could indicate it being aged.
@swathdiver has more info on the "battery state of charge" based on the resting voltages

**and coolant being low would be a reason for the fans to run at high speed more often because the cooling system is not able to do it's job properly
AND that is risky behavior in my book, the last thing I want is a overheated engine that's a pricey endeavor.

 

[OBSandaNNBS]

Yes there are 5 blade 700w fans, i just went with the hummer shroud because it is easily verified to be 700w, out of all the gmt900 junkyard vehicles I have been thru not one has been K5L, yet you see a ton of them listed on ebay as K5L.......
...

Thanks, that's some good info! Do higher number of blades equal more air movement (cooling)? That was an H2 or H3 with the 5.3? They are almost never at my local yard.

I think perhaps it's time to spring for a battery tester...I have a charger/alt tester but not a battery tester. But I will try the checks you suggested with my multimeter tomorrow.

As far as coolant goes, yeah, I agree. It's been on my mind. I've been medically out of it for a month, just getting back...wanted to do the tees, hoses, etc at the same time. I was more worried about one of them failing than I was the coolant level. All are original, yikes!
My problem isn't really fans turning on too often, just being really loud. I was worried about an electrical fault. Also temp dummy gauge has never gone over the middle.

 

[Doubeleive]

Thanks, that's some good info! Do higher number of blades equal more air movement (cooling)? That was an H2 or H3 with the 5.3? They are almost never at my local yard.

I think perhaps it's time to spring for a battery tester...I have a charger/alt tester but not a battery tester. But I will try the checks you suggested with my multimeter tomorrow.

As far as coolant goes, yeah, I agree. It's been on my mind. I've been medically out of it for a month, just getting back...wanted to do the tees, hoses, etc at the same time. I was more worried about one of them failing than I was the coolant level. All are original, yikes!
My problem isn't really fans turning on too often, just being really loud. I was worried about an electrical fault. Also temp dummy gauge has never gone over the middle.

hummer H2
I have yet to test if a 5/5 blade or 7/9 blade throws more air (finding such data online is nill)
I have also yet to test if a honeybee style grill or slotted grill allows more airflow
maybe next time I have to change out the radiator i will try to see what the fan flow rate is as I have a spare shroud
still looking for a slotted grill at the junkyards (mine is the denali with the honeybee)

 

[Doubeleive]

my goal with the fans was just more power obviously 700w is going to output more than 500w regardless of blade count in this circumstance anyway.
trying to find CFM data based on fan blade count, I had no luck, although i'm sure it's out there somewhere.

 

[Doubeleive]

AI's data

 

[j91z28d1]

my goal with the fans was just more power obviously 700w is going to output more than 500w regardless of blade count in this circumstance anyway.
trying to find CFM data based on fan blade count, I had no luck, although i'm sure it's out there somewhere.

electric motors are funny, they try run the rpm per volt they are wound for. so say the 500w and 700w are designed to run the same rpm per volt, the same fan blade on both would move the same amount of air and pull the same current. you would need that more aggressive fan blade to increase airflow. guessing that's the extra blades not more pitch, and the watt rating being higher just means the motor can handle the extra load. where putting that 7 fan blade on the 500watt motor it would draw the same current and shorten it's life because it was only designed for 500 watts.


either way this is all crap compared to the brushless fans of the next Gen up. I'm convinced that a new rad/brushless fan set up from them is a direct drop into our trucks, and then change one drop down box in hptuners. move the trigger wire from the stock relays to the pwm signal on the brushless fans, run the power straight to the alt lug, ground to the cyl head and have less current draw, more airflow. happier factory wiring without the fan load on it. higher voltage the the fans for more speed and variable speed, not just low and high.


sadly my hybrid doesn't have that drop down box defined in hpt to change from discrete output to pwm. it's a totally different ecm or I'd have taken the jump already. but I need a external controller and the only one I find that would work for mine is like 500$ alone.


blah. I will try this someday thou haha. I absolutely love the brushless fan conversion on my c6. one of the best mods I've done to it. the ac and everything is happier.

 

[swathdiver]

Thanks, that's some good info! Do higher number of blades equal more air movement (cooling)?

GM used more blades in the early designs and fewer later. I doubt that they would have compromised on airflow when making that change.

I have both the early and later design blades on my trucks and none of them want for more cooling with how they are used.

 

[OBSandaNNBS]

Yes there are 5 blade 700w fans, i just went with the hummer shroud because it is easily verified to be 700w, out of all the gmt900 junkyard vehicles I have been thru not one has been K5L, yet you see a ton of them listed on ebay as K5L.......
besides the fact I bought brand new 700 motors for it....
in any case all fan shrouds fit the same 00-14, 700w use the same relays and wiring. so nothing really to "write-up"
if a person were to upgrade it's 100% plug-n-play
as for voltage fluctuation I can only speculate based on my own experience which is when the battery gets weak, the voltage gauge shows a lot more movement. A good fresh battery will show 14v (center) on the gauge more often than a weaker battery which may show less than center more often.
Voltage should be more solid no flickering headlights or erratic stuff going on. (such as the fans surging)
the gauge fluctuation is normal regardless, it's more of a matter of "how much".
you can do some easy testing of the battery by checking the voltage with a meter in the morning before the 1st start and see where it is sitting after resting overnight, then check what the voltage is running after it has sat idle for more than 2 minutes, because at first startup the alternator is automatically commanded to give increased voltage for the first minute and half or so.
then check the battery again after you have drove it for the day (engine off) and compare that to the morning resting voltage, if it is dropping more than a little bit overnight that could indicate it being aged.
@swathdiver has more info on the "battery state of charge" based on the resting voltages

**and coolant being low would be a reason for the fans to run at high speed more often because the cooling system is not able to do it's job properly
AND that is risky behavior in my book, the last thing I want is a overheated engine that's a pricey endeavor.

Alright, it had 12.2 V this morning, cold. And 14.8 within 2 minutes.

12.2 seems a little low.

Also attached is my coolant level, cold. The truck is parked on a slight incline.

 

[Doubeleive]

Alright, it had 12.2 V this morning, cold. And 14.8 within 2 minutes.

12.2 seems a little low.

Also attached is my coolant level, cold. The truck is parked on a slight incline.

after you have driven it for the day and have parked it, then check the voltage engine-off record the voltage, then check it again tomorrow again before you start it. and compare
coolant doesn't really look very low, mine will sometimes rest just below the cold line. depends on how it was last flushed.

 

[OBSandaNNBS]

electric motors are funny, they try run the rpm per volt they are wound for. so say the 500w and 700w are designed to run the same rpm per volt, the same fan blade on both would move the same amount of air and pull the same current. you would need that more aggressive fan blade to increase airflow. guessing that's the extra blades not more pitch, and the watt rating being higher just means the motor can handle the extra load. where putting that 7 fan blade on the 500watt motor it would draw the same current and shorten it's life because it was only designed for 500 watts.


either way this is all crap compared to the brushless fans of the next Gen up. I'm convinced that a new rad/brushless fan set up from them is a direct drop into our trucks, and then change one drop down box in hptuners. move the trigger wire from the stock relays to the pwm signal on the brushless fans, run the power straight to the alt lug, ground to the cyl head and have less current draw, more airflow. happier factory wiring without the fan load on it. higher voltage the the fans for more speed and variable speed, not just low and high.


sadly my hybrid doesn't have that drop down box defined in hpt to change from discrete output to pwm. it's a totally different ecm or I'd have taken the jump already. but I need a external controller and the only one I find that would work for mine is like 500$ alone.


blah. I will try this someday thou haha. I absolutely love the brushless fan conversion on my c6. one of the best mods I've done to it. the ac and everything is happier.

That seems like a great mod. I would totally consider it when replacing the radiator. I wonder if the brushes could be wearing out, causing more pull and wearing out the battery faster?

 

[Doubeleive]

electric motors are funny, they try run the rpm per volt they are wound for. so say the 500w and 700w are designed to run the same rpm per volt, the same fan blade on both would move the same amount of air and pull the same current. you would need that more aggressive fan blade to increase airflow. guessing that's the extra blades not more pitch, and the watt rating being higher just means the motor can handle the extra load. where putting that 7 fan blade on the 500watt motor it would draw the same current and shorten it's life because it was only designed for 500 watts.


either way this is all crap compared to the brushless fans of the next Gen up. I'm convinced that a new rad/brushless fan set up from them is a direct drop into our trucks, and then change one drop down box in hptuners. move the trigger wire from the stock relays to the pwm signal on the brushless fans, run the power straight to the alt lug, ground to the cyl head and have less current draw, more airflow. happier factory wiring without the fan load on it. higher voltage the the fans for more speed and variable speed, not just low and high.


sadly my hybrid doesn't have that drop down box defined in hpt to change from discrete output to pwm. it's a totally different ecm or I'd have taken the jump already. but I need a external controller and the only one I find that would work for mine is like 500$ alone.


blah. I will try this someday thou haha. I absolutely love the brushless fan conversion on my c6. one of the best mods I've done to it. the ac and everything is happier.

ya the Silverado has the new fans, when I have been out off-roading or up at high elevation on a steep upgrade in the heat, the temp only goes up maybe a smidge then drops right back down, the fans seem to be pretty efficient. so far anyway... and I have the tru-cool dead center in front of them, the shutters are tuned off

 

[OBSandaNNBS]

ya the Silverado has the new fans, when I have been out off-roading or up at high elevation on a steep upgrade in the heat, the temp only goes up maybe a smidge then drops right back down, the fans seem to be pretty efficient. so far anyway... and I have the tru-cool dead center in front of them, the shutters are tuned off

The GMT900 Silverados have the brushless motors or new fan blade design?