Porter Cable 3-1/4 hp VS plunge router won't run at a speed less than 21,000 rpm

[Wes Billups]

I'm hoping someone can help me out on this subject. I've had this Porter Cable Model 7539 Type 1 router for about 22 years and don't think I've ever used any speed less than the max of 21,000 rpm (I don't own any big bits). Last night while trying to demonstrate the variable speed to someone I switched it to the lowest speed and when you pull the trigger it wouldn't turn the arbor:mad:. Same result at all other speeds. Even when I returned to the 21,000 rpm setting it took a couple tries before it fired up.

441901

I know Porter Cable routers have had issues with the speed control malfunctioning but everything I read talked about the router speed varying while cutting not failing to even startup. I also read about issues with the soft start caused by a faulty speed control but that also works fine at the top speed.

Tonight I played around with it a little more and noticed that if I start it up at the top speed and then switch to a slower speed I can hear the motor slow down and speed back up as I move the speed control switch. I then proceeded to take the router apart to see if I could find anything (I'm replacing both bearings so I was taking it apart anyway). No obvious issues or significant amount of dust in the switch. The brushes look great so I don't believe that's an issue.

Could this be caused by a bad bottom bearing? I'm assuming the issue will remain once I get new bearings but am hopeful there was just too much resistance for the motor to start it at the lower speeds due to a bad bearing.

I'd love to hear your thoughts and if anyone else has experienced this issue.

Thanks,
Wes

P.S. If anyone has recommendations on sources for new bearings in a router I'd appreciate that as well. I've been reading as much as I can and it appears there are more bearing grades than I have routers.

[Curt Harms]

I replaced the bottom bearing on a Freud FT2000E. It had a shielded bearing, I replaced it with a sealed bearing. I took the old bearing to a bearings and drives type store, they got me a new one. That router lives in a router lift so I imagine stuff drops onto that bearing more often than if it were used upright.

[Jim Becker]

Tonight I played around with it a little more and noticed that if I start it up at the top speed and then switch to a slower speed I can hear the motor slow down and speed back up as I move the speed control switch.

My gut is that this is an electronics problem since it speeds back up on its own.

[Wes Billups]

Sorry as I wasn't clear in my post. The router only speeds back up as I slide the speed switch to higher rpm's. It appears to respond appropriately with speed adjustments but only if the router is started at full speed.

[Richard Coers]

Those routers are almost antiques, technology wise. They frustrated me when new. I had one in a router table with a raised panel bit. They were so unresponsive when machining end grain. Almost intolerable. Your problem has nothing to do with a bearing.

[Bruce Wrenn]

Eons ago, I remember a couple posts about replacing the capacitors in the speed controller to fix speed problems on big PC routers. It's been over three years, and living in NC, the statute of limitations is three years, so I don't have to remember it exactly.

[Tom M King]

Try some contact cleaner in the slide switch. It's kept a number of my old tools going.

[Dave Sabo]

While the bearings may be bad , that electronic is not sophisticated enough to recognize that. There are some tools that do , and shut down operation completely. This is not one of them. PC controllers are notoriously weak links in an otherwise solid tool.

[Wes Billups]

Thanks for all the comments. I'm pretty much at a stand still until the new bearings come in and I can put the router together. Sounds like the consensus is the bearing and speed issue are not related.

I have the contact cleaner at the ready as soon as I get it all put back together.

Is there anything I can check out while the unit is completely taken apart? I know enough about electricity to be careful but am wondering if the speed control fluctuates the speed via changing frequency to the motor. I have the tools to measure voltage and amperage but not frequency. Is there anything I can check with a volt/ammeter that may help me trouble shoot the controller?

I will say before I took it all apart, when pulling the trigger with the selector switch at the lower speeds you could see the motor slightly rotate but probably less than 2° of movement.

Based on my limited knowledge I am tempted to follow Bruce's suggestion and look for the capacitors on the controller. I've never done anything like that but figure that's why they invented YouTube.

Thanks again for everyone's help. I'll continue to report back on what I find.

Wes

[Dave Sabo]

I’d replace the brushes while I had it taken apart.

[Curt Harms]

I had the variable speed fail on a P-C 8529. It started out hesitating before starting - nice slow start when it worked - and got slower, eventually got to where it didn't start at all. I removed the speed control module, wired the switch directly to the motor. If I want variable speed I bought an external speed controller. I haven't used the external speed control much at all but it seems to work. Set the speed to minimum and it's sort of like soft start. Downside is it makes the router less portable.