Gibson GR4GA war story and a great tool

[jb8103]

This Gibson is a package unit including furnace used on a mobile home. The place was abandoned for a year after the occupants were evicted. My brother will take over mobile homes like this, renovate, and sell, "just for beer money" as he puts it. Park management just gave it to him with 90 days free lot rent for fixup time.

He called me because the furnace wasn't working. The blower motor capacitor was missing and the capacitor leads were shorting against the housing. Motor was toast, shorted windings. Gibson OEM parts are hard to come by around here, especially for this monster, so I picked up a Fasco 220VAC 3-speed reversible off the shelf to substitute. The motor was too long to fit in the cabinet though, so I shifted the assembly inboard by an inch and clamped it. Worked fine for a week until the blower wheel shifted on the shaft and bound against the housing. This happened again a week later. So I used good old Loctite in the set screw, pity the next tech who has to work on it, but with a new motor I figured would last past the unit service life, no moral problems here.

A week or so later, the unit started tripping out on high limit. I told my brother there had to be an airflow problem. He didn't want to pay me to crawl around under there looking for it, so he went in himself. He got as far as the cold air return, a flex duct hanging by a few threads from the stack boot, when the unit failed again. This is all in his spare time, so the unit was left short-cycling for several days.

I found a seized up blower motor too hot to touch. Pulled the assembly, found shorted windings (low and medium-hi speeds) and one of the reversing leads was burned completely through. And I had glued the blower wheel in there, dang me.

The old pro trick of twisting the motor shaft with an adjustable wrench to free up the blower wheel wasn't gonna work. Down at the parts house I ordered the OEM Gibson blower motor for a pretty penny and told my sad story. No one knew whether to laugh or cry, but they did recommend the Ultimate Puller by Sensible Products for getting that motor out. I was skeptical but ordered one anyway.

This is a great tool. Fifty bucks well spent. Pushed the motor out of the wheel effortlessly, I didn't even feel any resistance. I highly recommend it.

Anyway, the motor hasn't come yet, so we're still in the thick of combat. For anyone interested I'll post the reports. But I'd like to know myself why that reversing lead burned through.

[RegUS_PatOff]

. . they did recommend the Ultimate Puller by Sensible Products for getting that motor out

Ultimate Puller UP-1 Ultimate Hub Fan Blade Blower Wheel Puller HVAC by Sensible Products

about $ 55

click on picture

OR

Supco FBP100 Fan Blade Puller about $ 35

click on picture

[applianceman18007260692]

2 speeds connected together will burn a motor up fast also any other speed wires should be taped off seperately so they won't short against the frame or each other. Electric blowers don't need but one speed anyway wide open. LOL all other wires should be put away where they won't misbehave.

[jb8103]

This motor plugs into a 6-pin connector, then I can pick the speeds at the circuit board. When high limit started tripping out, I changed the heat speed from medium high to high. Basically swapped the heat/cool connections. Kid brother promised to check all flex duct for obstructions that very day but of course, these things have a way of not happening. Anyway going to high speed maintained 69 degrees inside for a few days but I'm sure it was still tripping out at least occasionally.

Next thing we know, a few days later, we have a cooked motor with shorted windings and a burned-through reversing lead (the yellow side) and I'm not sure why. It was not likely a short against the cabinet as these are insulated quick-connects. When the new motor comes in, they say Monday, I'll get serious and check voltages and etcetera. I kind of suspect a goofy high limit switch, too, but usually these things either work or they don't, there's no intermittent failure. It's rated for 165 which seems low to me, but I didn't design this rocket so what do I know.

IMHO it's not a good idea to put a residential furnace out in the weather in upstate New York but it's quite common around here, on manufactured homes.

[ACtechGUY]

It is possible that your generic replacement motor was over - amping. I have found that not all motors are the same. A 1/2 hp OEM motor may be more powerful than a 1/2 hp generic replacement. I have had this problem several times . The replacement motor with EXACTLY the same specs would draw to much current and soon burn up. When the OEM motor is then installed, things are fine.

So the solution for me is the get the OEM motor whenever possible, to avoid that problem

Also if your motor was rubbing the side of the blower housing , that would cause overamping and a burnup as well.

The key is to check amp draw of the motor after you install it. If your motor is pulling a tenth of an amp over the rating of the motor , it will toast sooner or later. What happens if a motor is overamping is that the lubricant gets cooked out of the bearings due to overheating, then the motor ginds to a halt, and cooks itself to death.

[jb8103]

It is possible that your generic replacement motor was over - amping. I have found that not all motors are the same. A 1/2 hp OEM motor may be more powerful than a 1/2 hp generic replacement. I have had this problem several times . The replacement motor with EXACTLY the same specs would draw to much current and soon burn up. When the OEM motor is then installed, things are fine.

So the solution for me is the get the OEM motor whenever possible, to avoid that problem

Also if your motor was rubbing the side of the blower housing , that would cause overamping and a burnup as well.

The key is to check amp draw of the motor after you install it. If your motor is pulling a tenth of an amp over the rating of the motor , it will toast sooner or later. What happens if a motor is overamping is that the lubricant gets cooked out of the bearings due to overheating, then the motor ginds to a halt, and cooks itself to death.

Probably a combination of these factors, especially considering the blower wheel slid and jammed twice, leaving the motor stalled for hours each time.

OEM forever, my solemn oath. Or no warranty, so sorry.

Any insight as to why that reversing lead burned through? I can put up pix on Monday if helpful, that's when the new motor is supposed to appear and I go back over there for another round. I'm worried I'm making some knuckleheaded mistake on the install, and if I don't know what it is, I'll do it again.

Oh, there's another chapter here, my brother was using a couple of old Aladin kero heaters for heat. When I walked in the other night to pull the motor with my shiny new puller, it was like walking into a truck stop, they reeked so bad my eyes began to water. I pulled out my combustion analyzer and stuck the wand into the older of the two kero heaters. 2100 ppm of CO!!!! I kid you not. Way in the back of the mobile home, as far as I could get from the heaters, 170 ppm. We snuffed the heaters immediately, put 'em out in the snow, and opened all doors and windows. He's using electric heaters now.

[jb8103]

OK, we got the OEM blower motor in, an Emerson 3-speed non-reversing guy. All duct is checked for obstructions as far as we can see without tearing the place apart. If we try to drive the temp past 69 the unit still trips out on high limit, but it will maintain at 69. Motor amps 1.7 on the medium speed lead. Seems low, so I'm still convinced we have an obstruction somewhere. One tech I talked to today suggested a crack in the heat exchanger right near the high limit switch, making a hot spot. Hmm. Have to take a look in the daylight.

Then, this evening, his pressure switch failed, stuck open with inducer running. I pulled it out and did the suction test while checking for continuity. I could hear the contacts click closed but only got continuity on one out of three tries. I put it back in for jollies and the unit did fire up, but no doubt will fail sometime tonight, so portable electrics are redeployed.

What a piece of junk.

I think the loose blower wheel was due to a short set screw. The screw head was bottoming out before it got a good grip on the non-OEM motor shaft. So it felt tight, but it weren't where it counted.

[RegUS_PatOff]

. . . One tech I talked to today suggested a crack in the heat exchanger right near the high limit switch

hhmm . . . do you have a digital carbon monoxide tester ?

OR one of these :

click on picture

[jb8103]

I have a Bacharach Fyrite 60 combustion analyzer with CO detector. When the top is off this Gibson unit the heat exchanger is wide open for visual inspection, too. So we'll have a real close look in the vicinity of the high limit snap disk.

However there are no CO detectors in the house yet. They would have gone screaming meemies when he had his kerosene heaters going, CO levels were well past evacuation point. Definitely toxic, we were affected after two or three minutes.

[JumpSteady]

Ultimate Puller UP-1 Ultimate Hub Fan Blade Blower Wheel Puller HVAC by Sensible Products

about $ 55

click on picture

OR

Supco FBP100 Fan Blade Puller about $ 35

click on picture

I've got the supco puller. It works, but you have to be patient to line it up correctly, make sure the shaft lines up with the hole and that none of the 4 set bolts on the puller hit the hole for the fan blade set screw. I've done this and couldn't reuse the blade due to the damage.

[ACtechGUY]

It is possible that the reversing lead had a bad conection. That would cause it to burn up or discolor.

About the Hi limit tripping...

Have you taken a temperature reading at the supply duct ? Too high of a temp split would indicate an airflow problem of some sort.

I have also seen it where I had to adjust the gas pressure at the valve to lower the exchanger temp to a point where no trips would happen.

In regards to the pullers..I own , and have used the puller like the one in the bottom of the 2 images for at leat 13 years. I have never used the little arms that come with it for blower wheels. but it works great on condenser fan blades.... if they are not too rusted.

Tips for pulling:

1. sand the shaft so any rust is gone or very little.

2. Oil the shaft , so once the fan starts to move it does not bind. (use lubricating oil , not penetrating oil like wd40, penetrating oil is not very slippery)

3. Don't bother trying to pull a blade if the shaft and fan hub a very pitted with rust.

I have learned that when a fan blade gets to a certain level of rusted, NO PULLER in the word will ever get it off. There comes a time when you just buy that new 20 dollar fan blade instead of fighting for 5 hours to get that old rusted one off. Although anything can be separated without damage given enough time , patience and knowledge .

[jb8103]

Sorry it took so long to get back to this, here's what happened.

The unit failed again, as usual in the middle of the night. When I opened it up this time I found a completely destroyed blower wheel. Shredded. Hanging in sections of twisted metal. Holy mackerel, says I, or anyway words to that effect. The new motor checked out still good, so thank the Lord for that.

Kid brother is getting a little sick and tired of this but he bucks up $80 for a new wheel (Gibson OEM). My favorite local supply house just happened to have one.

We got that installed and problem solved. It's been weeks now and no further problems, nice even heat, good temp rise, and no tripping out.

My theory is that the wheel had taken too much punishment, was structurally weakened, and under load conditions was distorting to the point where it just couldn't push enough air through the heat exchanger. Finally it flew apart.

[dilkey]

i hate to differ with you guys but just replacing a motor means nothing, too me whats most important and so misunderstood is what is your static pressure? or esp, you can change motors all day but if your static pressure is comprimised like for example, a dirty blower wheel. or a dirty a coil, most run at .50 inches. i bet your over 1 inch, which will overamp a blower motor, i see it every day, this is only my opinion, i love my magnahelic guage.i wish more techs did this simple check.