Cruise control not working

[100K+]

The resistor mod to the CPS is straight forward. I managed and my electrical skill is limited. I did this repair about 3 years ago and its still working today.
Attached is a pic of my handiwork so u can see whats involved. The resistor was 5p from maplins

Cheers
Bob

[cheshired5]

Originally Posted by Jools99

if it's the clutch position sensor and you want to fix it yourself this link will hopefully be helpful

Originally Posted by 100K+

The resistor mod

Surely this modification removes the cruise control's ability to recognise pedal movement thus removing the automatic cancelling of cruise control when the clutch is moved?

[100K+]

Originally Posted by cheshired5

Surely this modification removes the cruise control's ability to recognise pedal movement thus removing the automatic cancelling of cruise control when the clutch is moved?

Short answer is no. My cruise works exactly as I would expect.

Longer answer .
The CPS is a simple potentiometer, the addition of the resistor (the value you have to calculate) - makes the potentiometer give readings in the required range, when the clutch pedal is at rest. ie up

At rest the reading is higher, (say 4500ohms) and when the "failure" occurs the reading is lower than necessary (say 2500 ohms) pushing the clutch pedal down in either option reduces the ohm reading to about 400 ohms.
Adding the resistor adds Ohms to the failure level of 2500, bring it back up to 4500. ( if you do the calculation correctly) It may also add ohms to the lower ohm reading too, but because the low figure is low it stays low ( I can't remember whether the addition is a finite number or a percentage of the ohm value) and the potentiometer works as required.

You know what Ohms you have, and what you need, and there is formula so that you can get from A to B.

Cheers

Bob

[cheshired5]

Originally Posted by 100K+

Short answer is no. My cruise works exactly as I would expect.

Longer answer .
The CPS is a simple potentiometer, the addition of the resistor (the value you have to calculate) - makes the potentiometer give readings in the required range, when the clutch pedal is at rest. ie up

At rest the reading is higher, (say 4500ohms) and when the "failure" occurs the reading is lower than necessary (say 2500 ohms) pushing the clutch pedal down in either option reduces the ohm reading to about 400 ohms.
Adding the resistor adds Ohms to the failure level of 2500, bring it back up to 4500. ( if you do the calculation correctly) It may also add ohms to the lower ohm reading too, but because the low figure is low it stays low ( I can't remember whether the addition is a finite number or a percentage of the ohm value) and the potentiometer works as required.

You know what Ohms you have, and what you need, and there is formula so that you can get from A to B.

Cheers

Bob

Thanks for the explanation.

When I cleaned mine up to fix it I found that it was reading correctly at either extreme (200-3000ohms) but in between when moving the spring loaded rod, the resistance would jump around erratically regardless of direction rather than uniformly falling and rising.
This would mean that with normal clutch operation, the return voltage would give the impression that the pedal was being violently moved in and out.
I summised that ECM thought, sod that and cancelled the cruise function.

Cleaning the carbon tracks essentially removed some of the carbon so there was a noticeable gap in the track, importantly however, there was no longer erratic resistance readings, just the high then the low.
The ECM is obviously happy with this as the fix has held for 3 years so far and is certainly worth anyone looking at this solution as a credible alternative especially if soldering isn't their forte..... which it isn't for me.

[benja]

Hi, I finally got round to testing my clutch position sensor, and as Im not sure what I'm doing I thought Id post the results to see if anyone can help me.

Image 1 - fully extended


IMG_0005.jpg


Image 1 - fully compressed


IMG_0006.jpg


It could be that at the compressed position it went off the scale, which would concur with correct operation.

I will have a closer inspection later this evening as to the scale and smoothness etc.

Ben

[100K+]

This is the site I used to calculate my " resistor" requirement to sort out my CPS. I'm still trying to find the actuakl figures you need


http://www.sengpielaudio.com/calculator-paralresist.htm

Cheers

Bob.

[100K+]

new figures are here

https://www.volvoforums.org.uk/showt...+clutch&page=2

Post 12

There are lots of other posts on subject on this forum -
search "resistor sensor ohm"

Cheers

Bob

[benja]

cruise now fixed!

I soldered a resistor in parallel:

image.jpg

It just about squeezed into the casing!

I didn't do any of the working out, I left that to a friend who worked it out and delivered the correct resistor to me!

It is a 4k3 one.... Doesn't mean much to me, but it is different to the one used above, different amounts of wear on the tracks?

Anyway, all works fine now.

I was unsure that the clutch would still cancel the cruise but it does.

Really easy job to do if you have someone to do the electric bit!

[davebb]

Originally Posted by 100K+

Short answer is no. My cruise works exactly as I would expect.

Longer answer .
The CPS is a simple potentiometer, the addition of the resistor (the value you have to calculate) - makes the potentiometer give readings in the required range, when the clutch pedal is at rest. ie up

At rest the reading is higher, (say 4500ohms) and when the "failure" occurs the reading is lower than necessary (say 2500 ohms) pushing the clutch pedal down in either option reduces the ohm reading to about 400 ohms.
Adding the resistor adds Ohms to the failure level of 2500, bring it back up to 4500. ( if you do the calculation correctly) It may also add ohms to the lower ohm reading too, but because the low figure is low it stays low ( I can't remember whether the addition is a finite number or a percentage of the ohm value) and the potentiometer works as required.

You know what Ohms you have, and what you need, and there is formula so that you can get from A to B.

Cheers

Bob

Hi adding a resistor across the terminals in parallel, reduces the resistance ,
when the carbon tracks are worn the resistance goes higher, so this brings it back down to what the ecu sees as correct,
Dave

[blacktshirt]

My cruise control doesn't light up,the Steering wheel controls are ok.
Tried the clutch down/up which made no difference.
Any ideas please before I have to find somebody with Vida?