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Finicky PTO Switch


HERO Maker

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We are on the long haul hunt for a different 5th wheel and trying to end our homeless situation. When we pull over to take a look at a possible rig, because of our cat, I like to keep the motor running and use the PTO to bump it up a bit to keep it in the "on" range.

 

But lately, when I do to engage the PTO, it doesn't come on! Not sure what is happening. Usually it turns on when I first start up the truck to get it warmed up and aired up. Usually no problem. I also have no problem putting it into cruise mode when on the hwy!

 

But it has been a real PITA lately. Tried shutting it all down and restarting, but doesn't work.

 

Anybody else have a history with this. I hate running back and restarting the truck to keep the air on. I really don't want to carry the cat into the office and "drop" her off there for awhile, but have done that.

 

What you all say?

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Rocky,

 

I assume you have the idle shut down turned "on" in your truck? I'm not electrical by any stretch of the imagination so can't help with the switch, but next time you're hooked up to the shop computer have them shut off the idle shut down and it will give you a backup to keep the truck running without the PTO.

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Remember the "clutch" and " brake" switches used to

" disengage" your cruise control also affect the operation of your PTO. The switches are just a small type of micro switch operated by lever action. The lever is actually a coiled piece of spring wire that acts like a coil spring.

These sometimes become disfigured after years of use. The older switches had limited adjustability to compensate for the wearing of the springs. Next time you have an issue try pulling up on your brake pedal and or your clutch pedal to see if it helps to engage the PTO. You may also hear the switch make a clinking noise when you pull up on the pedal. Sometimes a small buggy cord can be added to help hold up the pedal against the switch. This might explain why sometimes it works ok on at the beginning of the day before the pedals get moved around during driving. You could also have a " turn signal stalk" going bad. Some things to check out.

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Rocky - on ours, 2004 & 2007, both of them newer than yours, but you could do an engine speed up (fast idle) by cruise on, button on the end of the stalk, speed up, multiple presses, and your idle will come to 900 - 1000 rpm. When on fast idle, the auto shutdown should be disabled.

 

Now, having said that, ours is newer with a different software version, but worth a try.

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I have an 01 Volvo, too. The only thing that keeps my PTO from engaging is the Parking Brake is not on. I did a quick look and don't seem to have the appropriate electrical diagram on hand. Might be that a relay controlled by the pulling of the parking brake (dropped air to spring brakes) is not working. It is late tonight. I will try to hunt down the right schematic tomorrow.

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Thinking about what would cancel the high idle-

Clutch or brake pedal not fully released- (in the up position)

Both Red and Yellow knobs in the out position- releasing brake springs as Chet has mentioned)

The stalk itself. A quick search on Truckers forum shows this is a regular replacement part. Used are available on E-bay and it looks like a DIY repair.

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The truck is parked at the moment for a couple of days. When it happens again, I will lift up on the clutch and or the brake pedal to see if that allows me to engage the PTO.

On my truck, whenever I start it in the morning, I always engage the PTO and bump it up to speed up the air/warm up process. So brake knobs don't have anything to do with it, on mine.

A couple of time in the last week I wasn't able to engage the cruise, so if that happens again I will try lifting the clutch and or brake pedal also.

 

Thanks for reminding me about those micro switches. I think that MrSeas nailed it.

 

I'm hoping it's not the stalk. But sounds like it is pretty easy to replace. Thanks Jim.

 

Carl, I might just have to change the parameter if I ever get into the programing side. But I'm not sure I want to idle the truck very long with lower oil pressure. Once I bump it up, it remains at running pressure, but idle is about half of that. I thought I heard that was not a good idea?

 

Thanks guys,

 

Will report back Tuesday or Wednesday.

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I found the schematic for the CC/PTO/Engine Brake (thanks Mark!) on the Resource Guide. It is a very direct connect to the ECU. The ECU then gets inputs from various things mentioned to allow the engine rpm to be set or CC to be set.

 

What engine does your 01 have? Not that it makes much difference from what I see but there are different schematics. Mine is Detroit.

 

Things to ponder:

1. The CC works fine. That means the clutch switch is good, service brake is good, and the Turning Light Stalk switches are good.

2. What else controls the PTO when parked? Parking Brake, Transmission in Neutral, and most important, the ECU.

 

I went to the Owner's Manual. Page 101-103 describes setting the PTO. It says the only requirement is the clutch and service brake be released. There are two different types of PTO's, an Engine Mounted and a Transmission Mounted. The Engine mounted can be operated while moving. Don't even know which one I have. :rolleyes: It also shows a PTO switch that I don't know I have.

 

Here is something to see if the Parking Brake circuit is telling the ECU it is on. Chock the wheels. Release the Parking Brake. Turn off the engine. The headlights should be on.

 

One more question: Does the "PTO" telltale ever show up in the graphic display?

 

Wish I could be more help. Sounds like a trip to the dealer. :mellow:

 

Chet

 

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PTO stands for "power take off", for that extra boost when drag racing..... not really. While that is the meaning, it's to power an auxiliary pump or other device, such as a hydraulic pump to raise a dump bed. Usually mounted to the tranny.

 

So, say you're delivering a load of something, using a hydraulically driven motor to pump.....asphalt, fertilizer, etc. You engage the pto, then bump up the idle speed so yer not sitting there all day.

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Your new information about the CC not working all the time points to different causes. The clutch switch is very sensitive on mine. Just a slight touch and the CC drops off. That would be my first place to look.

 

The service brake switch is a different story as there is not one on the pedal. I thought mine was bad because the only thing turning on my brake lights and shutting off the CC by braking was the Hayes Brake Controller. So I tore open the cover on the clutch and brake to find a hole for a brake switch and nothing in it. I found that F31 had blown stopping the air-operated switch from sending a brake signal to the vehicle.

 

Chet

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Rocky. If you have been driving the truck you should have used the brake, but I have pulled out of a rest area from a stop when I didn't need to use the brake on exit (and didn't turn the truck off while in the rest area) and my cruise would not engage until I hit the brake pretty hard. (Cannot just tap it like if you were just disengaging the cruise). I have also had an occasional issue with the PTO setting, usually when I don't quite push the resume button far enough the first time. I then have to turn the cruise off and start again. The Idle setting can be adjusted by pushing up or down on the cruise button. Up for higher idle speeds and down for lower. Pushing resume and down at the same time does not change the idle speed and what I use when first starting the truck. Always hated that it went so high at first until I could get it slowed down. Otherwise I would wait before exiting the truck before engaging or hope I would get back before the idle shut down timer shut the truck down.

 

Sorry if I get windy sometimes. It's raining here so I can't go outside.

 

Rod

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VED12 is my engine.

 

Chet, that does make sense regarding the clutch switch. And do remember 1 time (although it was a while back) when while cruising it just dropped out! I know that my clutch hangs down just tiny bit, so the small lightweight bungy might be the fast fix.

 

I'm going out to take a look right now to see if I can see that switch.

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Thanks Rod,

 

I just looked at, and found that, both the clutch and the brake pedal have a little play in them from full top, to their resting position.

But I could certainly hear the switch when I depressed each one of them. Put a small bungy on the brake pedal (it had almost 1 1/2 inch of play) so we will see if it makes a difference. I will lift it with my toes when it does it again, and report back.

 

Thanks again.

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OK, we just pulled into Howe, IN, and had 3 different times that I went to engage the PTO to keep the a/c running. YES, it is the clutch switch that is causing it! Lifted it with my foot each time it wouldn't engage - and behold, it went it and stayed.

I will move my small bungy cord from the brake to the clutch tomorrow and see if that can stay a short term fix for now.

Thanks everyone. And if I were going to give lessons to anyone about how to engage your PTO, I would have said the same things you were telling me. And yes, your cruise control is your PTO when sitting still.

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Okay, back in my previous post, I was clear as mud.

 

I doubt that any of us have a PTO to engage. That would be another gear box on the side of the tranny. What we are actually doing is bumping the idle as if we were using a PTO for some function.

 

It might be nit picking, but we might as well be correct.

 

And Rocky, congratulations on finding the issue(s).

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Okay, I’m an easily confused neophyte just trying to follow this discussion. What rickeieio says makes sense to me … I think!

 

You see, I didn’t know what a PTO switch was, so I Googled and found it meant Power Take-Off switch, a way to use the truck’s engine to power things like dump beds. Then I got to thinking our Volvo 610 has nothing like that I know of. Hence the confusion.

 

Plus, our truck doesn’t cut off the idle, or if it does, it takes quite awhile to happen. Maybe that’s how the previous owner (Gail Quinn) had it programmed? Something I’ve picked up from reading here is that increasing the idle speed, using the CC controls, would make the AC more efficient. I didn’t know about that or how to do it. Thanks.

 

One more thing. A few months ago, after pulling out from an interstate rest area, the CC didn’t work. Tried it again a half hour later and it kicked in just fine. Now I’m thinking either the brake or the clutch pedal may not have been completely out. If it happens again, I’ll try pulling them out with my foot.

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Here is the real confusing thing with it all. When you engage the cruise control on my truck the display reads CC. When you engage the PTO in my truck (using the same controls as for Cruise) the display reads PTO in the same place that it read CC! Hows that for a surprise?!

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Rocky,

That is how mine works, too. I think the difference is the parking brake. No parking brake, the ECU says CC if the tractor is moving at 25 mph or more. Parking brake on, the ECU says PTO and gives you engine speed control via the turning light stalk. As soon as I push in the parking brake, the PTO indication drops out and the engine returns to idle and will shut down in about 10 minutes. I will get that programmed out when I can get to a reputable place to do it. The Volvo dealer in this area (Chesapeake, VA) has a bad rep and I have had one bad experience with them not to be repeated.

 

Even though the ECU will give us a PTO indication and engine speed control, most of us don't have the output drive (PTO box either on the motor or transmission) to power anything.

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Interesting, Rocky. I can't read the display except when I'm stationary and can look at it apart from the sun's glare and in just the right light. Hadn't noticed it said anything about either CC or PTO. But since we both have the same year Volvo, I'm guessing the displays are pretty similar. But you have a 770 while we have a 610, so maybe not.

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Here is the real confusing thing with it all. When you engage the cruise control on my truck the display reads CC. When you engage the PTO in my truck (using the same controls as for Cruise) the display reads PTO in the same place that it read CC! Hows that for a surprise?!

What if we rename everything associated with those buttons to engine RPM and Road Speed Adjustment (RSA)?

 

While stationary you are able to use the buttons to adjust the engine RPM from Idle to 1500 RPM. This is useful in "Wet Kit" trucks that have a hydraulic pump for various applications. It also works to build up air a bit faster or provide higher output from your electrical system (say you are using "Jumper Cables")

 

Once the truck is moving the road speed is what is used and not the RPM. Both adjust the amount of fuel provided to the engine same as the accelerator pedal. We used to have a cable with a knob that you would pull out to the desired RPM and then twist a collar to lock it in place. Worked good at keeping RPM , but not so good with road speed. Too fast going down hill and too slow going up.

 

Rod

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