850 Cruise control not working

Post by **abscate** » 29 Aug 2016, 05:14

On U.S. Models in 1999 the cruise light is on the far left side, the top row of idiot lights , so about 2 cm up from the bottom of the dash.

The problem is cruise on ME7 is disabled by many faults including any ETM fault. When you push the cruise button in this case, the cruise light does not light up. However, the cruise light does not light up in the position II ignition switch when every other light does ( which is a good bulb check feature)
I guess the bulbs do last a long time. I wonder if cruise disables if the bulb burns out? On the 1999 in sure it's DIM controlled so it would be buried in that logic circuit as opposed to an analog toggle in -1998 models

Post by **erikv11** » 29 Aug 2016, 08:27

erikv11 wrote:... We have that little snowflake telling us it is cold (OK I know it is more than that ...) but strangely, there is no cruise indicator light!

Really!

There is no indicator light of any kind (for the cruise cotrol) in an 850.

I know cruise instructions are in my car's owner's manual, I will check the page so we can see if it could be a market-specific difference.

zhenya · Post by **zhenya** » 29 Aug 2016, 08:54

I presume you verified this somehow in your testing, but just throwing out there that the wiring in the signal switch often breaks clean in these cars. I checked a bunch of other stuff in my '98 before peeling back the rubber boot at the stalk near the steering wheel where the broken wire was as obvious as could be.

Post by **erikv11** » 29 Aug 2016, 10:34

Just FYI the cruise info is on page 1:15 in the manual for my 96. I just looked online and the same info is on page 2:15 for a 97.

There's nothing very special in the manual other than pointing out the loose connection to ABS (spinning/locking wheels disengages cruise) but if your manual has it omitted for some reason:
http://new.volvocars.com/ownersdocs/199 ... 5.htm#2:15
http://new.volvocars.com/ownersdocs/199 ... htm#pg1.15

Post by **scot850** » 29 Aug 2016, 11:21

I did say the info is in the handbook for the 97 I have, but it is not listed in the index, so I had to check page by page to find it.

Yes it make the cruise control difficult to figure when there is no 'engaged' light to even let you know it works! Another dumb idea from Volvo in the past.

I've removed the cover from the switch but there does not appear to be any obvious broken wires where I thought there may be in the boot area of the switch, so I will now just have to test it with my meter and if any doubt try another unit for comparison. I have also swapped out the controller relay for another one from PnP as there is no easy way to test it.

Thanks for the help again!

Neil.

Post by **scot850** » 29 Aug 2016, 12:38

Ok, I appreciate I am a mere mortal mech eng, but really the pdf file I believe was written by an idiot, unless my dyslexia is really bad today.

I ran the tests for the cruise switch as per the instructions. Basically testing power is going to the switch, switch works in ON position, set + and set - work and resume. In all cases you are testing for 12V DC when the button is activated. When the + an - set buttons or resume are released the voltage in the top connector at the pins drops to 0V.

To check the actual control unit you remove it and test between ground and a particular pin as specified. What cracks me up is when you press any of the buttons you are checking for 12V at the switch, but the instructions say if you test the relevant contact at the relay, when you activate the switch you should get 0V or the switch it faulty and replace it? Now considering you only get 12V when the switch is activated and the voltage drops to 0V when released, don't they mean you have a faulty switch IF the voltage does NOT drop to 0V after release of the button? Otherwise you would have 0V at all conditions of switch operation!! Am I missing something here as a simple mech eng?

Assuming they have written a bunch of crap, then I'd say all the electrical portion of the switch is operating as it should, and I swapped the relay for good measure.

So, unless the electrical switch on the brake pedal is faulty I'm hoping a test run this afternoon may have a chance.

Next, I ran a test on the Neutral start switch resistance. The result should be 0 ohms. I got 11 ohms. Is that ok? The switch works as I'd expect.

Lastly, I was going to do the brake-light switch test. #1) - So first thing it says, if you press the brake pedal and the brake lights come on there is a wiring fault. Eh? The brake light should come on if you press it. Do they mean you have to remove the relay or something else, and then if the brake light comes on there is a possible short in the wiring?

Ho-hum. Just love those technical writers.............................

Neil.

Post by **scot850** » 29 Aug 2016, 15:23

Well I have had success. In-spite of the crazy writers and their technical nonsense, the cruise now is working. Still not sure what the issue was, or if I in retrospect didn't realise it was working (although I'm 90% sure it wasn't) as there was no cruise activated light in the 850! It is a little slow to activate at first also.

Only parts replaced were the vacuum pump (original had a hole in the body but not sure it was an issue) and the controller relay courtesy of my local PnP. Switch tested out good.

So if you take the pdf and use it as a somewhat confusing guide it will get you there, but you have to interpret and extrapolate some of the information! Cost of parts =$12 US!!

Thanks for your help guys and forgive the belly-aching!

Neil.

zhenya · Post by **zhenya** » 29 Aug 2016, 17:47

Glad it is working. The P80 cruise is indeed very slow to activate. It also is somewhat of a mystery to me how the +/- speed buttons are supposed to work. Sometimes they seem to add speed correlating to how many clicks I give them, sometimes it seems like I have to hold the button until I reach my desired speed. Both of my cars seem to mostly behave as the latter case. Not the most elegant part of an otherwise solid car, or maybe both my cruise switches are just aged?

Post by **abscate** » 29 Aug 2016, 17:53

zhenya wrote:I presume you verified this somehow in your testing, but just throwing out there that the wiring in the signal switch often breaks clean in these cars. I checked a bunch of other stuff in my '98 before peeling back the rubber boot at the stalk near the steering wheel where the broken wire was as obvious as could be.

Analysis of the cruise is beyond the scope of the novice mechanic. I needed sophisticated equipment to troubleshoot mine

: image.jpeg (105.25 KiB) Viewed 1389 times

Post by **scot850** » 29 Aug 2016, 18:08

Show off with the fancy equipment!!

What I need to get is a variable voltage supply to test parts out of the car.

The +/- buttons are suppose to add about 1.6km/1mph up or down if you believe the literature!

Thanks again guys!

Now off to find something else to fix - just done the door check strap, now pull the heater motor and clean it out and the evaporator or pull the head-light and fix the chipped glass and non-functional wiper motor. Choice, choices....!

Neil.