Blower runs for 30 seconds then quits


  #1  
Old 07-21-08, 04:05 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Blower runs for 30 seconds then quits

I bought this house last year. It was a repo. There is no info to be had on its history before me.

A/C has been working fine this summer until yesterday. I'll include a few possibly helpful symptoms from the winter heating months also.

Forced air, split system
Snyder General built in 1989
Model GUD100A020ATM

Outside -
compressor and fan both run when called by the thermostat. Nothing looks out of the ordinary. Fins are pretty clean and there's no debris in or around the unit.
I did notice a small amount of icing on the line. I don't know if that line was "in" or "out". (this is where the little bit that I do know, ends)

Inside -
The filter was dirty. Actually, it was really grungy. Okay, the truth is, it was caked with muck. No, I've never changed it before. Lesson learned... it wont ever get like that again.
Fins on the fan inside the blower housing are a little dusty on the surface, but there's nothing caked on, just a fine layer of ordinary looking dust. It spins freely in either direction by hand.
The back side of the motor is caked with grunge. It's thick and paste-like.
There is no visibly apparent bulging on the capacitor
All connections are snug and nothing changed or was touched from when it was working 3 days ago, to yesterday when I turned the system on after being gone for the weekend.

When I adjust the thermostat to trigger cooling, the compressor and outside fan start right up and continue to run until I tell it to stop by adjusting the t-stat. The inside fan will come on after about a minute, run for 30 seconds then shut off. It will come on occasionally and repeat the shutoff. With cooling off or on, I can turn the fan switch to "ON" from the t-stat, and the same thing happens (starts after a minute, then shuts off after 30 seconds).

In winter both in this year and last year, I had fan problems with it not coming on at all when set to Auto. If I turned the t-stat fan switch to ON it would come on and stay on till I turned it off.

It's getting power, because it does come on, it just doesn't stay on.

Following the wires around, there's a fan limit switch (set at on/off: 80/125 and off: 190, a capacitor that isn't bulging but is 20 years old, and a little chunky black plastic thing (a relay?).

I really can't afford a service call right now.

Any help with diagnosing the problem would be appreciated.

Also, what would be the appropriate way to clean the gunk off the back of the motor? Carb cleaner works great on most sources of gunk on my dirt bikes... but I'm thinking it's not the best choice in this situation.

Thanks in advance for your words of wisdom....
 
  #2  
Old 07-21-08, 07:29 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Fan short cycles

If you have a volt meter & know how to use it, make sure the motor is getting power when it shuts down on its own. If it is not getting power you will have to trace the circuit backward to find out why. If it is getting power, the capacitor could be weak & causing the shut down. From what you have said about things being dirty, my guess is the motor is getting hot internally & shutting itself off. You are likely going to have to replace the motor. When you do so, replace the capacitor as well.
 
  #3  
Old 07-22-08, 07:25 AM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Originally Posted by DesertRacer
The inside fan will come on after about a minute, run for 30 seconds then shut off. It will come on occasionally and repeat the shutoff. With cooling off or on, I can turn the fan switch to "ON" from the t-stat, and the same thing happens (starts after a minute, then shuts off after 30 seconds).
Does your fan plug into a board and have separate terminals for heat and cool? Any place you can take voltmeter readings like that?, where you can see if 120 volts is being interrupted before it even gets TO the blower fan? Obviously you will have to stay there and make sure you are continously testing for your 30 seconds and longer.

At worst you could cut the wire, [WITH THE POWER OFF, NATURALLY] (IF you have slack enough in the wire to wire nut them back together again when you are done), and then with one voltmeter lead touch the incoming hot wire to the fan and the other test lead to any sheetmetal (or ground) on the furnace )(with the power back on to the furnace now for testing, when you are ready) , that is not painted. This will establish for you if the probem is in your fan or with a relay before it.

Your "on-off-limit" numbers are actually "off-on-limit", instead - and that comes into play for your heating circuit.

In winter both in this year and last year, I had fan problems with it not coming on at all when set to Auto. If I turned the t-stat fan switch to ON it would come on and stay on till I turned it off.
In "ON" it is supposed to stay on, forever.


It's getting power, because it does come on, it just doesn't stay on.
Well, there is no limit switch for cold as there is for the fan switch in the winter, so my guess is you have either something wrong in the cooling speed windings of that motor (which you can find out by that volt test I mentioned above), or some relay that somehow is not staying "closed".


I really can't afford a service call right now.

Any help with diagnosing the problem would be appreciated.
And that is the whole idea of this forum, and hopefully if we continue (we, being several of us here), dialogue back and forth here, the problem can get pinned down.

Also, what would be the appropriate way to clean the gunk off the back of the motor? Carb cleaner works great on most sources of gunk on my dirt bikes... but I'm thinking it's not the best choice in this situation.
Kind of like greasy dust trying to get in the slots? I'd just vacuum out what I can, or use an air compressor. You can even rig up a staw, or flexible vauum tube, to the end of the vacuum nozzle to create a small crevice tool. I've done that. But do not use it long that way, as the restriction is hard on the vacuum motor.

..............

Or what Grady said, makes sense. But you should be able to find out by the test if you lose power before the motor or not.
 
  #4  
Old 07-22-08, 04:40 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Grady and ecman51`,

Thanks for making me finally learn how to use this multimeter.

In the meantime, I traced the relay controller (JA1C-TN-AC24V-F) to be equivalent to Intercity Products Blower Relay Controller 24 Volt Coil 1 H.P. 125 VAC. AMPS:10 and the capacitor (Cambridge 1200-026) to an equivalent of Compressor Single Round Run Capacitor 10.0 MFD 370 Volt.

I tested all the connections from where the power comes in, through all the terminals where it stops off and goes back out again, all the way to the last wires that connect into the back of the blower motor. I have a lot of information, but no idea what to do with it. I rounded the values, so hopefully that's okay.

When t-stat is set to AUTO:
120 on incoming black wire (poked the tip into the wire nuts with a bunch of other wires) Then there are wires that go out to a little relay and then go out to the motor and to the limit switch.

On the relay:
COM = 120
NC = 120
NO = 0
2 other connectors go out to t-stat wiring, both read about 2.8v

The capacitor reads zero, on both terminals

When t-stat is set to ON, motor is running or not:
120 at the incoming black wire.
On the relay:
COM=120 (running=118)
NC = 0
NO = 120 (running=118)
wires out to tstat -
blue/grey? is 2.9
brown is 11.9 off and 12.2 running
The capacitor reads 122 on both terminals when not running and 2.4 on one terminal, 22 on the other while running.

On the limit switch (i know it has to do with heating, but I had fan issues in the winter when it was set to auto - it wouldn't turn on unless it was turned ON, and the burner wouldn't stay lit come to think of it - wow, I think I'm an idiot!)

In AUTO
Load FAN Line terminal is zero, and the terminal below that is also zero.
terminals on the left are 12v on top - load limit line, and zero on the bottom

In ON mode
Load FAN Line terminal is 120 when not running and 189 when running. the terminal below that is 0 all the time.
Load Limit line is 12v on the top and bottom terminals, running or not.

There is another couple of red wires that go up from the limit switch and the red wire in the fan motor wiring to a simple little block of two terminals sticking out of a small base plate. Both of those terminals read 12v all the time.

As noted, in some places, the voltage drops or increases to a different number, but none of the values change from zero to "something" or from "something" to zero when the fan motor shuts off while in ON mode from the t-stat.

Sorry if the descriptions sound so "homeowner". I have tried to find a manual or even a parts diagram to better identify things, but am coming up empty.

I am gathering from your replies that it is probably a bad capacitor with a high chance of a motor that is also burned out?

Is it safe to try replacing the capacitor and see if that resolves the cycling problem?

Or will that just mask a bigger problem of a capacitor killed by a bad motor that could actually do some serious damage (fire, etc?) if the motor is not replaced too?

I'll fix it right, I just don't want to replace parts that aren't bad.

I appreciate the help so far, I'm learning a lot!
 

Last edited by DesertRacer; 07-22-08 at 06:33 PM.
  #5  
Old 07-22-08, 06:21 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Capacitor

One can't test a capacitor with a voltmeter. Capacitors are cheap if you want to try just replacing it. If that doesn't fix the problem, you are probably looking at a motor.
 
  #6  
Old 07-22-08, 06:45 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Lots of figures. Almost overwhelming. Really was looking for COOL and on AUTO settings to see where you may have power and then where it gets lost.

Grady says motor after replacing cheap capacitor. Could be.

But with all your testing so far, you have nothing to lose but a few minutes in ohms testing all the colored wires on your motor (except the 2 brown ones if you have those),taking readings between a colored wire and the (white) neutral wire to see what resistance readings are. And tell us what they are for each color (various rpm speed wires) of the motor.

And also try testing between any of those colored motor wires and ground the other probe of your meter to the motor housing to see if any of them, testing each one at a time, indicate a short(passage of of any current); should not pass any current at all (IOW, ohm meter should stay dead)
 
  #7  
Old 07-22-08, 06:55 PM
The Real Deal's Avatar
Member
Join Date: May 2008
Location: Texas
Posts: 146
Upvotes: 0
Received 0 Upvotes on 0 Posts
After reading all the posts!

A hunch - Sounds like the Blower motor could be a replacement motor that is the wrong one - This would explain its cycling - if it is the wrong RPM - HP... it will cycle. Resistance of the blower wheel when turning, will be wrong for the design of speed and Horse power of the unmatched motor.

If it is the correct motor after all - Replace Cap -Then Replace the motor in that order.

* Providing you have checked for power and you have it to the windings when the motor is in its "off cycle"

* If you end up replacing the blower motor - DONT go off the old one in this case - Call a supplier of that unit and ask them to reseach the unit with model and serial number to get the correct one.
 
  #8  
Old 07-25-08, 03:41 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Fixed!

Okay guys....

The request for ohm / resistance info pushed me beyond my zone. After letting the smoke out of my multimeter, I figured I better not hurt myself. I got a new one that doesn't make me think (the other one made you choose a range, and I had it on too low a setting). Anyway, I don't have info to report, since I didn't write anything down. I made a call to the person I didn't want to call in the first place, my ex hubby, and he was actually sporting enough to walk me through the remainder of the troubleshooting steps you guys were talking about. He's an hvac service tech, life-long career, so you can appreciate the irony here.

Final verdict: The squirrel died. I first replaced the capicitor, no help, and then the motor, and now all is well. Total Cost to repair: $120. I owe you guys a big thanks. You called it right.

Reasons/Causes and writing on the wall .... low rpm speed wasn't working at all, which explains why the fan wouldn't come on in Auto when using heat last winter. I could turn the fan ON, (higher rpm) and it would work. I had no idea there were two (and potentially more) speeds! In AC mode or just the fan, at high speed it would start to run, but overheated fast and shut itself down. The more I tested, the shorter the window that it would stay running, to get a reading on a connection.

When I pulled the motor, the shaft was super gunky, with a lot of corrosion and hard, rust-like buildup that extended all the way down into the motor. It smelled "warm" and all the windings were coated with crud and in some places, they even look melted. It was really hard to get the shaft out of the cage. I cleaned that with brillo and WD, and the new motor shaft slid in easy. There's a number on the motor plate that appears to denote a manufacture date: 1989, corresponding with the age of the unit. The part number was old and discontinued; it's been in there a long time, so I'm confident that matching specs got me an an appropriate replacement. It was also a motor that calls for being oiled every six months. I will bet it's NEVER been oiled.

I'm not usually one to be happy just with fixing something and not knowing why it broke. If I know the root cause, it's safer to say I've actually fixed the problem. Then I can prevent it from happening again. It was worth a couple extra days playing with it, I didn't even care that's it's been over 100 degrees here all week.

I really appreciate the tips and troubleshooting steps that helped me learn a great deal. I was really proud to stand there at the supply house and ask for the part I knew I needed, and knowing that I knew how to install it! (I actually enjoyed the good-natured ribbing from the contractors there, who asked several times if I was sure I could handle it) I also picked up a year's supply of new filters.

My experience speaks volumes for the absolute necessity for regular maintenance.

Appreciate the help. That was fun.

Devon
 
  #9  
Old 07-25-08, 03:49 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Glad you got the problem at hand, fixed.

But what I'm wondering about now is the gunky rust. Maybe condensation water in A-coil pan overflowed due to backed up condensate line or bad pan? You don't want your next motor to be prematurely getting wrecked, needlessly.
 
  #10  
Old 07-25-08, 04:15 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Smoked Meter

Yeah, they are packed with smoke at the factory & once you let it out, they are done. Don't feel bad. I'm sure most of us who work with meters all the time have smoked one or two. I know I have.

Congrats on fixing the motor problem but as ecman said, you need to find out why that motor was rusty.

Be careful when oiling the new motor. If the instructions say 3 drops, that's what they mean, not 10 or 30 drops. More motors die from over oiling than lack of oil.
 
  #11  
Old 07-25-08, 05:50 PM
D
Member
Thread Starter
Join Date: Jul 2008
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Yeah, I wondered about the rust too since this is the motor in the furnace in the garage. It's not a package unit, and the condenser is outside.

At one time in this house before I owned it, there had been a water damage insurance claim. It was pretty extensive, and involved parts of the garage. That's all I know. The unit is on a platform close to the water heater. There is a bunch of water pipe running in the vicinity, as well as lines to a water softening unit that froze up and exploded while the house was empty in the winter after the bank foreclosed on it. They didn't winterize, and it gets down in the teens here at night in winter. I can guess that those incidents might have had something to do with it. I dismantled the water softener system when I moved in.

There is no current water leak, but if there is still moisture or condensation in the cabinet with the water heater (which I keep open, not closed like the previous owners probably did) there's not much more I can do to abate that, short of move the unit or the water heater. The previous motor survived 17+ years in the worst conditions... so I'll just know to keep an eye on this and at least know what to look for in early warning signs.

 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: