Blower motor 3/4 speed tripped/reset c/b... but c/b is 40a

[jackb]

While driving yesterday, my blower motor 3/4 speeds cut out. 1/2 still worked, and 3/4 came back online a few minutes later. I know this means the c/b tripped, and then reset, so I checked it today expecting to see some corrosion, or too low of a c/b (25a instead of 30a).

I pulled the cover today and it’s a 40a c/b. I had replaced the original c/b last year with one from DMCCA (I was unaware of the size at the time, just used the one Danny Botkin handed me).

So what gives? 30a shouldn’t trip like that and 40a definitely shouldn’t. Is my blower motor on the way out/pulling too much current? It functions fine and makes no weird noises. I use it on speed 4 the vast majority of the time (Las Vegas).

[Gregadeth]

Make sure you're looking at the circuit breaker for the blower motor and not the cooling fans. They're right next to eachother and they could be installed in the wrong slot. The blower motor circuit breaker should have four wires, the cooling fans' has only two.

[jackb]

Make sure you're looking at the circuit breaker for the blower motor and not the cooling fans. They're right next to eachother and they could be installed in the wrong slot. The blower motor circuit breaker should have four wires, the cooling fans' has only two.

Yes, I am. It’s the only c/b I have. I've replaced the cooling fan c/b with Dave/bitsyncmaster’s fused relay.

[AugustneverEnds]

How does the spade connector on the blower motor itself look? I had a poor connection there and it would cut out on speed 4 but was fine otherwise. Also check the connection to the blower motor resistor.

[David T]

The cooling fans are supposed to have the 40 A C/B, not the cabin fan. If the C/B is popping it could be the fan motor is on it's "last legs" or the C/B is bad. Check the current draw.

[Bitsyncmaster]

You would need to measure the fan current on speed 4 to determine if the fan or circuit breaker is bad. It may just be you have a bad breaker. To measure the current you would probably need a clamp on type of DC current meter since the normal current draw I think is around 25 amps on speed #4.

[jackb]

I pulled the resistor and it appears to be in good condition. IDK which pins should give how much resistance, so I didn’t measure it.
The male end of the power connection on the motor though looks like it has overheated and melted the rubber surrounding it.

60909

I’m off to Lowes to see if I can “rent” an amp meter.

[Bitsyncmaster]

I’m off to Lowes to see if I can “rent” an amp meter.

Most mutimeter amp limit is 10 amps. Many even fuse that range. Your going to pull much more than 10 amps.

[jackb]

Most mutimeter amp limit is 10 amps. Many even fuse that range. Your going to pull much more than 10 amps.

Do you have any advice on how to isolate the problem to the motor?

[Bitsyncmaster]

Do you have any advice on how to isolate the problem to the motor?

I don't have this meter but from the description it does look like it will read DC current and is not very expensive.

https://www.amazon.com/Meterk-Multimeter-Auto-ranging-Capacitance-Non-contact/dp/B0721MKXBC/ref=pd_lpo_sbs_60_t_0?_encoding=UTF8&psc=1&refRID=G86HVYDHNBF5W380VKMZ

[jackb]

I don't have this meter but from the description it does look like it will read DC current and is not very expensive.

https://www.amazon.com/Meterk-Multimeter-Auto-ranging-Capacitance-Non-contact/dp/B0721MKXBC/ref=pd_lpo_sbs_60_t_0?_encoding=UTF8&psc=1&refRID=G86HVYDHNBF5W380VKMZ

Oh, you mean the clamp style instead of probe style. That’s what I got last night; I didn’t know the exact term for it. I picked one up from Home Depot last night. I’ll be measuring the current draw tonight.

[Bitsyncmaster]

Oh, you mean the clamp style instead of probe style. That’s what I got last night; I didn’t know the exact term for it. I picked one up from Home Depot last night. I’ll be measuring the current draw tonight.

I hope it does DC current. A lot of the cheap ones only work with AC current.

[jackb]

I picked up one that measures DC at Home Depot.
The current draw on each speed is normal...
#1- 2.48
#2- 5.84
#3- 10.59
#4- 13.9

I didn’t run it until the c/b tripped, but it has only happened maybe twice before, ever.
So everything is fine, until the breaker trips for an unknown reason.

I’m going to replace that 40a breaker with a 25a, but that does not solve my mystery problem.
The connections on the breaker look good, but I’m going to replace them with ring terminals as well anyway.

Any ideas?
The problem did fix itself, but I’m at a loss how to isolate the root cause to prevent it from rising up again.

[jackb]

Upon further inspection, I recognized I have 4 wires on my c/b.

The wiring diagram shows only three- one in (live at all times) and two out (one to each fan speed relay).

My car has 4 wires, two on the input, two on the output.
One of the input wires originates from the starter relay. The other three go into the harness. All are brown.

What is the mystery fourth wire for?

[Bitsyncmaster]

I picked up one that measures DC at Home Depot.
The current draw on each speed is normal...
#1- 2.48
#2- 5.84
#3- 10.59
#4- 13.9

I didn’t run it until the c/b tripped, but it has only happened maybe twice before, ever.
So everything is fine, until the breaker trips for an unknown reason.

I’m going to replace that 40a breaker with a 25a, but that does not solve my mystery problem.
The connections on the breaker look good, but I’m going to replace them with ring terminals as well anyway.

Any ideas?
The problem did fix itself, but I’m at a loss how to isolate the root cause to prevent it from rising up again.

Those seem like rally low currents from what I remember testing my blower. Did you check them with the engine running? I will check mine again.

The blower breaker should have 4 wires with the added wire on the "batt" side for the start relay modification. Yes it's a good idea to replace those quick connect terminals with ring terminals.

[jackb]

Those currents were all with the engine idling.
Before those measurements I checked it off battery only and each speed was about 1 amp lower.

[mluder]

Following this as I'm having a similar problem.

A couple years ago I was loosing fan speed 4 and replaced the relay for that (#24). Fixed it great.
Now the entire thing stops regardless of speed. After about two to three minutes it comes back (I can hear the click from the relay compartment). I assumed the speed 3 relay was bad as I think it controls 1-3 and speed 4 is added to it with the second relay.
Anyway, I attempted swapping it with my high beam relay but that didn't fix it.

For the last several months I've been getting some squealing on initial start up of the fan... I assume the bearings are going. It goes away after a few seconds.
Is it possible the increase in friction from bad bearings is causing the fan to draw more power and trip the breaker?

EDIT: Just did a little more research and i see now there's a circuit breaker #19 that controls the blower. I'm thinking that's my issue. Will check it out.

Cheers
Steve

[Bitsyncmaster]

I checked my blower currents putting the current clamp over the blower wire only, at the blower location. Engine was idling and my idle voltage is 14.6 volts. Room temp is 78 deg. F and mode switch on vent.

1 = 3.06 amp
2 = 6.91 amp
3 = 12.8 amp
4 = 17.6 amp

Now technically if the blower motor was hotter the current would go down a little not counting any bearing load changes. I wonder if some blowers have higher current since the recall changed the 25 amp breaker to a 30 amp breaker. Or maybe because the breaker temperature being higher in the closed relay compartment made it trip below the rated current.

[jackb]

My engine voltage is typically just under 13 at idle. If I start it up right now in a not-boiling hot garage (ambient ~85*-90*) I'll get 13 or a hair under. If I'm driving around and its over 100* outside, when I stop at a light I tend to hold the rpm's a little bit because at a true idle it will drop closer to just above the mark between the 8 and 13. My alternator is from DMC-CA replaced in 2011.

[Ron]

What kind of alternator is it?
If it is a GM style and the light comes on when the key is on then goes off once running, a very common reason for low voltage is the pulley is to big. GM basically has 2 sizes, most of which are the larger one. They have a larger drive pulley than Ds...
(It should never get down to 12V, running.)

[jackb]

What kind of alternator is it?
If it is a GM style and the light comes on when the key is on then goes off once running, a very common reason for low voltage is the pulley is to big. GM basically has 2 sizes, most of which are the larger one. They have a larger drive pulley than Ds...
(It should never get down to 12V, running.)

It’s from DMC-CA. The computer printed invoice says 105a, the handwritten one doesn’t specify. Same part number (110101) on their website currently describes it as 120a. Mine is from 2011 though, so it’s quite possible the actual item changed since then. The pulley is correct. I have fine voltage when driving, just at idle (especially when super hot) does it get low.

6092160920

Having low idle voltage should be a separate issue than the blower motor tripping a 40a c/b though, no?

[Ron]

It’s from DMC-CA. The computer printed invoice says 105a, the handwritten one doesn’t specify. Same part number (110101) on their website currently describes it as 120a. Mine is from 2011 though, so it’s quite possible the actual item changed since then. The pulley is correct. I have fine voltage when driving, just at idle (especially when super hot) does it get low.

6092160920

Having low idle voltage should be a separate issue than the blower motor tripping a 40a c/b though, no?

All 12V cars should keep the voltage at 12+ during idle (~13.5+ is normal). That's with stock accessories on. Ds are known to fall short with the stock alternators/age/etc., but one with an alternator rated 90 amps or more should never go below 12V. A D with a 105 Amp alternator shouldn't go below 13.5 volts. So, if you are getting "just above the mark between the 8 and 13" =? 11V while the engine is running, something is wrong.

You didn't mention the voltage above idle, so I'm assuming it is ok (~13.5 or more). IF that is the case and the alternator itself is OK, it needs to turn faster -- You said the pulley is correct. How do you know?
FWIW, it only makes sense, with the info so far, that the pulley is too big, to me. We've seen this a lot on after market units. And you report the problem goes away when you raise the RPM a little.....

=====

Yes. Although low voltage can cause things to heat up and make things worse, low idle voltage should be a separate issue from the breaker tripping.
I agree that the 40 Amp breaker might be bad considering the Amp readings you are getting. But you might need to let it run longer and see what you read after the blower motor has had ample time to get 'hot'...
You said you were going to replace the breaker with a 25 Amp. That's too low.

EDIT: meant to say too "big" (fixed).

[DMC-Ron]

Wouldn't the alternator pulley be too large if it was not charging well at low RPM?

[Ron]

Wouldn't the alternator pulley be too large if it was not charging well at low RPM?
Yeah, I said "big" in post 20 with an explanation as to why. ...no idea where the brain fart came from other than thinking about the remote possibility of the drive pulley being changed and dismissing it while typing...or ??

THANKS Ron!!! ...um, it seems I'm talking to myself now...too...goodby.

[jackb]

Out for a drive today, I paid extra close attention to exactly what the voltmeter did under what conditions.
Start it up, 13 volts. While still idling, within a minute, it dropped to 11.
While driving it would get up to 13, but not always- Sometimes only 12.5ish.
And pretty consistently if the engine was at idle speed (as in not pressing the gas pedal even while driving in gear) it would drop below 13. As low as 11 when stopped/idling in neutral.

I pulled the alternator and brought it to Oreillys to get tested. It puts out 14.5 volts and passed all tests. I cleaned the grounds/bracket (there was no corrosion or anything to cause a poor ground anyway).

The plug harness was in less than optimal condition it had a few breaks in the coating and corrosion. I ordered a new one and will get it tomorrow afternoon. I know this wire is only supposed to illuminate the battery light on the instrument cluster, but I want to eliminate any potential issues. The battery light does illuminate when the key is on/engine off, and turns off while the engine is running (despite the low voltage (the test indicated the light would turn on at 11v; the lowest I’ve gotten w/ a multimeter on the battery post in the engine compartment while idling is 11.5v)

As for the original issue of the blower motor, I got a new 30a c/b and put ring terminals on each wire instead of the clip style. I did not have any issues today with the clip style connectors and the old c/b before I changed them.

[Ron]

Out for a drive today, I paid extra close attention to exactly what the voltmeter did under what conditions.
Start it up, 13 volts. While still idling, within a minute, it dropped to 11.
While driving it would get up to 13, but not always- Sometimes only 12.5ish.
And pretty consistently if the engine was at idle speed (as in not pressing the gas pedal even while driving in gear) it would drop below 13. As low as 11 when stopped/idling in neutral.

I pulled the alternator and brought it to Oreillys to get tested. It puts out 14.5 volts and passed all tests. I cleaned the grounds/bracket (there was no corrosion or anything to cause a poor ground anyway).

The plug harness was in less than optimal condition it had a few breaks in the coating and corrosion. I ordered a new one and will get it tomorrow afternoon. I know this wire is only supposed to illuminate the battery light on the instrument cluster, but I want to eliminate any potential issues. The battery light does illuminate when the key is on/engine off, and turns off while the engine is running (despite the low voltage (the test indicated the light would turn on at 11v; the lowest I’ve gotten w/ a multimeter on the battery post in the engine compartment while idling is 11.5v)

As for the original issue of the blower motor, I got a new 30a c/b and put ring terminals on each wire instead of the clip style. I did not have any issues today with the clip style connectors and the old c/b before I changed them.
Just for kicks, measure your (D)rive and (A)lternator pulleys.
Your AlternatorRPM = D/A x EngineRPM, which should be 1800-2000 at idle for proper output.

FWIW, the Brown/Yellow wire also feeds the internal voltage regulator's excitation or field circuit. Some of the later style regulators are self exciting (w/wo revving). Either way, once it kicks in, the alternator should perform correctly until the key is turned off. So, that connection shouldn't have been causing the low output.

(Waiting on a fuse to blow is worse than, water to boil ;-)

[jackb]

None of this solves the original blower motor mystery, but hopefully that was just a bad c/b. Between the new 30a c/b and replacing the connections with ring terminals, hopefully it does not resurface.

(5.8 crank/2.8 alternator) x 800 idle rpm (approx) = 1660. Pretty close.

Voltage off - 12.38
Key on - 12.0
Idling - 14.0-14.3
Headlights on - 14.18
Aic conditioning only - 12.5
Headlights and a/c - 12.3

And then it hit me. It’s the cooling fans. The cooling fans are on almost constantly on my car. In hindsight I recognized the pattern. I’ve been doing very little highway driving and lots of street driving, in the summer, in Las Vegas. The a/c is almost alway running, therefore, my cooling fans are almost always running. And the controlled measurements of voltage confirm it’s my cooling fans that are pulling all this current. They are the original style fans. One was replaced in 2005 by the previous-previous owner, and the other I believe is factory original.

Of course, I just returned the ampmeter to Home Depot last night, so I’ll go rent it again and check the current each fan pulls.
What is the normal/acceptable current per fan?

[Bitsyncmaster]

Of course, I just returned the ampmeter to Home Depot last night, so I’ll go rent it again and check the current each fan pulls.
What is the normal/acceptable current per fan?

The Vendors low power fans seem to run between 7 to 9 amps each. I've tested a few OEM fans that run about 14 amps each but even those are ones that have burned up the fan fail socket and jumpers. Not sure what the currents are when the car is moving at highway speeds.

[Ron]

None of this solves the original blower motor mystery, but hopefully that was just a bad c/b. Between the new 30a c/b and replacing the connections with ring terminals, hopefully it does not resurface.

(5.8 crank/2.8 alternator) x 800 idle rpm (approx) = 1660. Pretty close.

Voltage off - 12.38
Key on - 12.0
Idling - 14.0-14.3
Headlights on - 14.18
Aic conditioning only - 12.5
Headlights and a/c - 12.3

And then it hit me. It’s the cooling fans. The cooling fans are on almost constantly on my car. In hindsight I recognized the pattern. I’ve been doing very little highway driving and lots of street driving, in the summer, in Las Vegas. The a/c is almost alway running, therefore, my cooling fans are almost always running. And the controlled measurements of voltage confirm it’s my cooling fans that are pulling all this current. They are the original style fans. One was replaced in 2005 by the previous-previous owner, and the other I believe is factory original.

Of course, I just returned the ampmeter to Home Depot last night, so I’ll go rent it again and check the current each fan pulls.
What is the normal/acceptable current per fan?
Those reading would indicate that the fans were drawing too much current if these regulators simply turned the alternators on an off like some of the older systems. But internal regulators increase and decrease the field circuit, varying the output, to keep up with the demand. So if the alternator is not at minimum speed at idle, it could already be putting out ~all it can at the point before you turn on the AC. When you then turn the AC (2 cooling and 1 blower fans) on, it wouldn't be able to keep up and the voltage would fall. So the readings might be misleading...

Something not mentioned- If the voltage is actually being brought down too low (whether it is the pulley and/or fans), the system will start using the battery instead of running off of the alternator alone and the light should come on.
Does it?

Whether the fans draw too much or not, 1660 is not close enough -- 1800-2000 is a minimum!

[jackb]

No, the battery light only comes on before I start the car. It does not come on while running despite the low voltage indication on the gauge.

The volts I listed above I took off the jump post in the engine bay (intake manifold for ground).

I just measured the cooling fans current: one is 8.85 and the other is 9.00. (Tested by starting up the car and forcing them on by turning on the a/c).

The alternator tested good when I had it measured the other day.
60945

Does this look like an alternator anyway? Or the pulley? (The pulley was replaced by DMCH when I changed the alternator in 2011. The 2.8” I measured was at the outside of the belts groove; what size should the pulley be?).
Or something else entirely?

[Ron]

No, the battery light only comes on before I start the car. It does not come on while running despite the low voltage indication on the gauge.

The volts I listed above I took off the jump post in the engine bay (intake manifold for ground).

I just measured the cooling fans current: one is 8.85 and the other is 9.00. (Tested by starting up the car and forcing them on by turning on the a/c).

The alternator tested good when I had it measured the other day.
60945

Does this look like an alternator anyway? Or the pulley? (The pulley was replaced by DMCH when I changed the alternator in 2011. The 2.8” I measured was at the outside of the belts groove; what size should the pulley be?).
Or something else entirely?
I'd say the alternator is OK (and the light doesn't come on when the gauge is low because you haven't waited long enough for the actual voltage to get low enough). And since nothing says you are drawing too much power so far, other than low voltage while idling (which goes away when you raise it a relatively few RPM), there is nothing left but the pulley size. Like I said before, we have seen this a lot with the "high amp" D alternators.

V-belt pulleys are measured across the outside of the pulley. (It really don't matter where as long as you measure both the same way since it is the ratio you're after....) You would need a 2 1/2" or smaller pulley to reach 1800 RPM. I would go with 2 3/8" (1954 RPM). Both are common alternator pulley sizes for V-belts.

FWIW- The alternator is probably a GM style/knockoff (that had a serpentine belt pulley). I just checked the pulley on my Blazer and it has a 2 3/8" pulley. There are two very common GM single V-belt pulleys. The (too) large one is usually stamped steel and the one that should work is billet (usually aluminum/steel). The smaller GM double pulleys will work in a pinch. Any alternator shop can hook you up.
If you swap the pulley yourself, make sure the rotor stays forward and does not turn when the nut is loose. This prevents damage to the brush holder inside.

EDIT: GM 2 3/8" at Summit Racing HERE (https://www.summitracing.com/parts/pwm-110?seid=srese1&gclid=EAIaIQobChMIo6ij-vCS5AIVgySGCh1SLA-NEAQYASABEgI_hvD_BwE) -- Check your belt width and ID before ordering...

[jackb]

Fixed!

It ended up being none of the suspected things.
I remeasured the pulley when the engine/exhaust wasn’t a million degrees and got 2.6” (I probably pinched tge belt with my caliper the first time when I got 2.8”). Thake makes my alternator rpm 1784.

The original plug on the alternator that I replaced had only one wire (the L wire). The new plug had 4. I crimped a terminal onto the S wire and connected it to the output post and viola! I have 14.3 at idle and 13.5 when the fans are on!

So that takes care of my low voltage, and (hopefully) the c/b replacement will ensure my blower motor doesn’t cut off again.

Consider this one case closed.