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Discussion Starter · #1 ·
With all the talk on the forum lately about unplugging the rear accelerometer to disable the 4C system I decided to give it a try. When I went to unplug the sensor, I discovered that the bolt holding the sensor had come a little bit loose allowing the sensor to rattle around a little bit.

I unplugged the sensor (disabling the 4C) and the ride did seem to improve. I then tightened the bolt holding the accelerometer down and plugged it back in and the ride was still better than it had been. I think that solved some if not most of my rear hop problem.

It's easy to check! You might want to take a look at your car and make sure the sensor is still firmly mounted to the body.

2004 V70R, Sum 4 update, Rear bushing update, Evolve springs.
 

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Re: Rear end hop? Harsh ride? Check this! (shelby_sho)

By accelerometer, do you mean this little thing?



I just checked mine, and its flapping all over the place. It was definitely loose. I've tightened it, and I'll go out for a drive and report back on the difference.

It really was pretty loose - any little bump would have upset the thing. Nice catch, Shelby!
 

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Re: Rear end hop? Harsh ride? Check this! (MASH)

On a V, it's on the left side - I'm not sure where it is on an S. It took quite a bit of effort to actually tighten the bolt - I finally got it an it's much more stable. Im off to take a ride right now.........
 

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Re: Rear end hop? Harsh ride? Check this! (MASH)

Left behind the fuse panel door. Not sure if there's one on the right but I think there is maybe under the bumper.

Agreed nice find Shelby. May I suggest a little Locktite?
 

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Re: Rear end hop? Harsh ride? Check this! (MASH)

on the V, it is the left side

this is odd, because almost a year ago I had my car in for the bushing/sum update for the hop, it came back to me worse than before...brought it back in, they had a regional tech look at it and he found my accelerometer was loose. I wonder if these things are prone to get loose. (Volvo are you reading?)

Makes perfect sense that the suspension would be total crap with one of these things banging around, sending god knows what sort of deflection feedback to the computer.
 

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Re: Rear end hop? Harsh ride? Check this! (kenschel)

I just returned from a 15 minute drive after tightening the accelerometer (if the thing in my photo is indeed the accelerometer), and I must say the car feels much tighter. I tried it over a slight left curve with a recessed manhole cover that always gets my car to hop in comfort, and it didn't do it (I have the latest bushings, alignment specs, and relatively new PS2's too). I took it over that manhole cover three times in comfort, and it felt much more like an XC70 than it did previously. My three year old daughter said: "why do we keep turning around, Dad?"

In sport mode it felt tighter, and there was almost no lift on WOT upshifts, and less dive under heavy braking. I could also feel more undulations in the road in sport - ala advanced, but without the harshness.

I'd say it's definitely worth checking to see if yours is loose.
 

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Discussion Starter · #8 ·
The picture is of the correct part. Wish I would have found it before I had the bushing TNN and SUM recalibration done.

I put a lock washer between the bracket and the bolt head.
 

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Re: (shelby_sho)

Anyone know where the accelerometer is on the S60R within the trunk?

2nd question: Anyone know how many TOTAL accelerometers there are in these cars, and their locations?
 

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Re: (shelby_sho)

the hop has been terrible on my car since I switched to PS2s. I was going to take it in for an alignment. I just checked and found the accel very slightly loose. I tightened it down and we'll see if it's better tomorrow. anyone know where to look for the other sensors? IIRC there are two at the front of the car, one on each side.
 

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Re: (StaggRLee)

Quote, originally posted by StaggRLee »
Same location. Left trunk cubby hole. Checked mine and it's secure. Not sure where the others are.

Found mine in same spot and it was tight. In my car it was just a little more hidden due to the DVD-ROM drive for NAV





LTA
 

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Re: (vizwiz)

There are two accelerometers in the front, that measure vertical BODY movement. They are located just below each headlight.

They must be secure and they must be positioned with the terminals facing up.

There are two more accelerometers located on each spring strut. They measure vertical speed changes of the SUSPENSION.
 

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Re: (rogersampson)

Quote, originally posted by rogersampson »
There are two accelerometers in the front, that measure vertical BODY movement. They are located just below each headlight.

They must be secure and they must be positioned with the terminals facing up.

There are two more accelerometers located on each spring strut. They measure vertical speed changes of the SUSPENSION.

Rogersampson: Are you saying what I found (see my pics above) and what Grendel (see his pic near the top) are NOT one of the rear accelerometers?

LTA
 

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Re: (LTA)

Sorry, I should have been more clear. I was responding to the inquiry in regard to the FRONT sensors.

The picture you show is indeed the REAR accelerometer, of which there is only one. It measures the speed of vertical BODY movement.

There are two POSITION sensors in the rear. They are located under the body near the coil springs, on each side. They measure the angle of the suspension in relation to the body, and the link arm attached to the sensor. These are the sensors that need to be "recalibrated", or actually their output, if they are ever changed or if there is a spring change that impacts ride height. Note these sensors are more like position encoders, and not really accelerometers.
 

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Re: (rogersampson)

That clears it up, thanks RogerSampsom!

LTA
 

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I'm with vizwiz, is there any way to get at the front accelerometers Roger?

Also, what about yaw? From what I gathered from you Roger, it seems that the system is only concerned with vertical accelerations, within both the body and suspension, and the angle at which the control arms are to the car.

Actually, I think the latter might be what i'm talking about...but if anyone could clear any of this up that would be fantastic, because sure enough, the trunk accelerometer was barely held down.
 

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Re: Rear end hop? Harsh ride? Check this! (StaggRLee)

Quote, originally posted by StaggRLee »
*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*

Oh wow, stagg! your new sig is just so... 80's and VT52. Real blast from the past http://********************/smile/emthup.gif But where are the Hayes AT control characters?
 

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Re: Rear end hop? Harsh ride? Check this! (shelby_sho)

First off, thanks to all who responded to my query about harsh ride. Tires (Michelins) were already at 33psi. The Volvo dealer just did the SUM IV update. My impression is that it helped a lot -- (in comfort setting)reduced harshness, seems to help isolate some road cracks, potholes, etc. Steering feels slightly more vague (is that related to SUM IV udate?). Didn't notice if it helped the rear end hop (shop calls it "sidestepping). The savvy shop foreman said some customers have had this update accomplished and then asked to have it un-done. Anyhow, trade off is better for me.

2004 V70R 6 spd 30K miles.
 
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