Add cruise control on 96' european 850 wagon?

Py · Post by Py » 22 Jun 2008, 01:41

Hello,

I'm nearly done fixing all the little annoyances my new car suffered of (really nothing major - and it only has about 65.000 mi (105.000 km) on the clock!)

Now one thing that the car doesn't have and I really would like to add is cruise control. It may sound weird to some of you, as I think all US cars were fitted with a cruise control (wasn't an option), but unfortunately, it wasn't that way here in Europe.

Nevertheless, googl'ing around I figured there are aftermarket units that can be fitted, and it doesn't look impossible to achieve myself.

Now, perhaps I'm better off using an original volvo cruise control than one of those aftermarket units? I've no clue about them all. Perhaps the components can be unmounted from a "cars junk yard" vehicle, if you see what I mean, and mounted back on my car? Is it simply possible? But how would that fit with my car's electronic controllers et all ? Is the system complex?

Thanks for any advice regarding the best path on that matter!

Post by **MadeInJapan** » 22 Jun 2008, 05:29

Not sure about after market but for the OEM setup, you would need:
1. Control Module (relay).
2. New turn signal arm with cruise control switch
3. Switch to go with your brake pedal to disengage the cruise control as well as servo switch for your accelerator pedal.
4. Vacuum lines and vacuum pump for the cruise control to go under your battery compartment.
5. All the routing of these hoses.
6. Possibly a new ECU (Computer) that will recognize all of this and control it...
7. Possibly more stuff that I can't think of right now.

Py · Post by Py » 22 Jun 2008, 08:43

Regarding the OEM setup:

Do you mean I would have to change the complete engine ECU, or are you talking about another, dedicated ECU?

This stuff is on sale on ebay: http://cgi.ebay.com/ebaymotors/ws/eBayI ... 17610&rd=1

Is it a complete engine ECU, or is it "just" the cruise control computer?

I also feels like I read another post (can't find it now) about asking a Volvo dealer to "download" the cruise control software into one's car ECU after having all the parts installed.

What's the final word about it? I suppose that changing the complete engin ECU is not trivial, as I would have to find one from the same engine model/year, but which had a cruise control fitted, than somehow get it reset, to let it "re-learn" its parameter inside my car when installed. At this point, the dealer having a way to download the software into the ECU makes more sense as I doubt Volvo has manufactured loads of immutables ECU variants depending on the options fitted...

Post by **MadeInJapan** » 22 Jun 2008, 09:00

The picture from eBay is the complete ECU...there is no such thing as an ECU just for the cruise control. Also, on these older (850) ECU's there is no flashing them to make them so they include the cruise...they either did or they didn't. I'm fairly certain that even if you fit your car with all of the right parts, without an ECU that is programmed to work the cruise, it will just sit there and do nothing...plus, if anything were to go wrong with the cruise, you won't be able to diagnose it because these signals will be absent. That said, yes, there are downloads to enable the cruise control, but these are for newer Volvo's running ME7 ECU's and not the older Motronic or FENIX ECU that your car has.

Py · Post by Py » 22 Jun 2008, 09:16

Ok, that does make sense!

So, I would have it swap my current Fenix 5.2 ECU for another one from same engine car, but WITH cruise control support...

Py · Post by Py » 23 Jun 2008, 08:10

I've looked around a little bit more, and regarding price and installation ease, it seems that an aftermarket ("universal") unit is probably a better solution. I'm not very fond of the idea of changing the engine's ECU, but maybe I'm wrong to be afraid?

Anyway, it seems there are 2 kinds of command servos: vacuum or electric powered.

As the OEM cruise control system does include a separate vacuum pump, I guess there is no proper vacuum source available on the engine itself. Or maybe they designed it this way to have the same unit to fit both N/A and turbo engines. As I have a N/A engine, there should be a way to get vacuum somehow, without adding a pump. Does it make sense?

Also, it seems that those aftermarket systems do require a speed "pulse-per-mile" signal. Other workaround solution is to fit a magnet on some rotating part, like a bicycle speedometer. Is such a "ppm" signal available somewhere on the volvo?

Las but not least, I would greatly prefer to use the standard command stalk, and not add a cheap looking add-in command pad. Maybe adapters exist for the command unit? I think I've more homework to do to figure out this one...

Post by **MadeInJapan** » 23 Jun 2008, 08:29

Good luck to you...I think this is going to be a PITA for you. You might do a search over on the VolvoSpeed forum...someone's got to have done this mod before...a signal from the wheel speed sensor (a splice) comes to mind for the rpm input. Anyway, like I said before, good luck! Btw, I have an 850 stalk with the cruise control switch sitting around somewhere but the wires will need to be spliced...previous owner cut the connector off.

Py · Post by Py » 23 Jun 2008, 13:38

Well, before deciding, I'll go on investing. Looking under the hood, I figured 2 things:

1) There is a neat second (unused) grove in the throttle pulley, as if it was waiting for a second throttle cable. OEM cruise control cable probably gets fixed there. But I can as well use it for any cruise control, be it Volvo or not.

2) And there are vacuum ports available! So, I probably need no vacuum pump at all (this probably looks different on turbo engines...)

So, it's not looking that bad so far...

Regarding ECU swap, if I have the proper replacement unit, is there a risk or special procedure to follow to change it, or is it a simple "plug & play" operation?

MadeInJapan, nice to know you have a stalk. I'll remember that if I need to find one

Post by **MadeInJapan** » 23 Jun 2008, 17:06

I think you still need a pump....if I recall, boosting up a hill requires more than the typical amount of vacuum in the lines. Good luck and let us know what you decide to do. As far as I know, if the ECU is for a cruise control, it will recognize it immediately. Your best bet might be to find one cheap from Ebay USA if you decide to convert.

Py · Post by Py » 27 Jun 2008, 06:43

As I "found" (;-)) a copy of VADIS, I was able to further dig for informations regarding the OEM cruise control setup.

VADIS has a complete and very clear technical description of how the whole system works. The most interesting point is that the engine's ECU is not at all involved in the process. VADIS is very clear about that. To make a long story short, the whole system is managed by the Control Module. It is the part looking like a double relay, and located in the fuses box. It gets the Vehicle Speed Signal from the speedometer, and controls the vacuum pump/regulator.

So, the parts needed to perform the upgrade are
-replacement command stalk
-control module (as said previously, in the fuses box)
-pedal valves (2x, these are combined electric/vacuum valves)
-vacuum servo (acts directly on the throttle pedal)
-vacuum pump and regulator (it is one integrated unit, located under the battery tray)

Some vacuum piping is obviously also required, as are the required mounting brackets, screws, ...

The only thing I still need to verify is if the electrical cabling for the vacuum pump and for the command stalk are already present or not. I guess they are...

Next step would be to find a donor vehicle in some kind of "pick-a-part", to grab all the aforementioned components.

Are some of these components known to be prone to failure (to consider buying them new from the beginning) ?