Adding Cruise to SC - HELP

Shawzy · 08-01-2003, 10:48 AM

Have all the parts required to slap cruise control on my SC (servo, brain, hoses, switches, etc.)

I can't find any wiring harness in the SC to hook things up to!

I was told that the "wiring harness for cruise should already be there, all you need to do is bolt in the stuff...."

Could this be incorrect? I.e. did all SC's come from the factory with cruise wiring or no?

Frustrated here, any help appreciated.

ruf-porsche · ruf-porsche's Garage

Why would someone go out and buy the Ultimate Driving Machine and then go and have a servo and vacuum hose and a brain (?) do the driving? Oophs this isn't the BMW board sorry.

Formerly Steve Wilkinson · 08-01-2003, 11:20 AM

Agree! First thing I tore off my SC when I bought it. What I particularly love about cruise-control users is that they'll do 65 to pass someone going 64, because that's what they've got the CC set on. The 20-minute pass...

Stephan

Shawzy · 08-01-2003, 11:52 AM

I hate driving the 911 so I would love a mechanical device to do some of the work.

If anyone else has any brilliant and helpful comments I am all ears. If the porsche cruise system bites, then someone tell me so I can consider an aftermarket. I am a big fan of cruise on 10 hr highway drives when the right leg is cramped.

RichMason · RichMason's Garage

wish I could help...cruise control is one reason I am considering moving up to a Carrera. Just because you like to give your foot a rest and maximize your predictability and fuel economy doesn't mean you can't appreciate a 911. Double-clutching works well too but I don't see many 911 owners tearing out their synchros. And being really cold would probably make the 911 experience more real and raw but I'll bet most of us still have heater boxes.

clnilsen · clnilsen's Garage

Quote:

Originally posted by Shawzy
I hate driving the 911 so I would love a mechanical device to do some of the work.

If anyone else has any brilliant and helpful comments I am all ears. If the porsche cruise system bites, then someone tell me so I can consider an aftermarket. I am a big fan of cruise on 10 hr highway drives when the right

leg is cramped.

Shawzy.

First, if you want to retrofit, you're goign to have to build a harness yourself. This is not a plug and play deal, unfortunately. I would suggest chekcing periodically on ebay for a NOS cruise kit, or going with an aftermarket deal.

Other than loosing the stock look of the switch, I'd say it's a better idea to go with something you KNOW is working as opposed to something that was taken out and of questionable pedigree. The brain boxes for these tend to be finickey, and you could spend ages after you get it installed troubleshooting it.

Hope that helps.

Chuck

BTW, I did a NOS dealer kit I got off ebay.. works like a charm.

Chuck

Shawzy · 08-01-2003, 02:02 PM

Thanks Chuck.

I can handle the wiring with any luck, but like you say I could get everything in and still have to troubleshoot the used parts I have acquired. If I have to fight with wiring, I would much rather install something I know will work. I hear the aftermarket are a little more robust and smoother when operating also.

I went the OEM route initially under the assumption my wiring harness was ready for it. Unfort, I could not check it out first hand until today.

Thanks again - will post when all is said and done.

If anyone else can give me any reason to stick with the OEM route please do so because right now I am looking at getting rid of it.

Shawzy · 08-01-2003, 02:03 PM

Chuck - what was the exact NOS kit you grabbed anyway? Model #?

clnilsen · clnilsen's Garage

Unfortunately, no, I don't know what the part number was.

Got it from Parts Obsolete.. I think he's sitting on a bunch of the NOS kits from the 70's and puts a few out at a time.

Check w/ Wayne too. Maybe he's got something? I don't know if Wayne carries NOS odd parts tho. Give him a call.

Chuck

island911 · 08-02-2003, 04:27 PM

Quote:

Originally posted by Shawzy
. . . .
I was told that the "wiring harness for cruise should already be there, all you need to do is bolt in the stuff...."
. . .

This is where to look if it is there.

. . .and what the plug look like.

RoninLB · 08-02-2003, 05:04 PM

I went thru the cruse control act.. my car didn't have the harness, and I couldn't get a harness for over a year.. I wanted the stock install for a clean blood line.. so I went with more exhaust noise which keeps the eyeballs from glancing all the time at the speedo.. I still may do the aftermarket someday and keep the controls stashed away I think a full aftermarket is under $150

Shawzy · 08-04-2003, 11:21 AM

Thanks for the pics island!

Alas, I have searched the area and no harness to be found. I Can't imagine it is buried somewhere. I have also searched in the engine comp for the servo cable, but no luck.

I guess my SC does not have the wiring.

I spoke with ROSTRA - makers of aftermarket cruise. Their brain doesn't work with the SC speedo signal apparently (needs a signal from an ECM). They suggested a magnetic setup around the driveshaft in order to grab a speedo signal their brain can use - I don't want to go there. Their kit is about $270US where I am - more than I want to spend.

Those with aftermarket or non-OEM cruise units, what's the deal with the speedo signal? Does the SC signal limit cruise kits to pre-80? I.e. No current designs are compatible? No idea what this signal output is when talking to aftermarket tech support.

Perhaps I should wander to the wreckers and grab a cruise kit off an old caddie. That and the suspension.

clnilsen · clnilsen's Garage

I use the magnet setup.. 4 little madnets jbwelded on the shaft. they're really small, so no worries about out of balance or anything.

Works really well, I used it this weekend!

Chuck

ohecht · 08-10-2003, 12:03 PM

I finally got tired of swapping parts and troubleshooting the OEM cruise, which I am told is finicky even when it works.

I finally (just) put in an SCS digital system that costs about $180. It works great, and I wired it so that it uses the factory switch (with some internal modifications). I put the same system in my Jeep Wrangler, and it is better than anything stock. No vacuum connections at all, just an electronic servo that is digitally controlled. SCS is an OEM supplier to car makers, and I think the system is the same one you can find on the Rostra site.

I have a few brains and stock servos if anyone wants them to work on a stock system.

Olivier

Shawzy · 08-31-2003, 02:36 PM

Just wanted to say that I have installed the OEM cruise in my 79SC and finally got it working this morning.

Got great support from members Island911 and ohecht (Glenn and Oliver) - many thanks to them. Love this board!

Physical install was easy, error in Bentley and Porsche manual 'cruise troubleshooting test' were a PITA (brake switch wire test specifically). Now that I have it figured out, everything seems fine.

Doing a 22hr drive to east coast in october, cruise will be handy.

I have some great self-learned tips if anyone wants to install OEM cruise or troubleshoot their current system - may post as a separate thread, but it seems not many are interested in cruise. Feel free to PM me.

island911 · 08-31-2003, 09:47 PM

Quote:

Originally posted by Shawzy
Just wanted to say that I have installed the OEM cruise in my 79SC and finally got it working this morning.. . ..

That's great! No easy task, but you did it!

W'hoo!

RoninLB · 08-31-2003, 10:53 PM

Quote:

Originally posted by Shawzy

Just wanted to say that I have installed the OEM cruise in my 79SC and finally got it working this morning.

great news but what happened to your aftermarket install?
I read that it was a great install with the stock switch.. and did you use a stock harness? it's nice to know of the stock switch to aftermarket cruise.

anyway there was a bracket up-grade in the engine comp. from the very old design, but I can't say now when the up-grade happened.

ohecht · 09-01-2003, 04:48 AM

I am glad that you got it working, it is nice for long drives and high-risk ticket areas, but I don't use it too often, either, except to make sure it is still working!

Ronin, I am the one that switched to the aftermarket SCS digital unit. It works great, and I was able to use the stock switch after changing the one momentary-open setting to a momentary-closed action.

The servo mounted in the stock location, and I reused the original two wires running to it for the clutch/brake interrupt signal. I did have to run the rest of the aftermarket switch wires from the servo in the engine compartment to the old brain location in the trunk, since the aftermarket servo has the "brain" integrated with the servo in the engine compartment. I tapped into all of the switch signals at the old brain harness in the trunk, so it is easily reversible. The one exception was my speed signal, which I got right from the speedo, and I think that was my original problem with my stock system (no speed signal at the brain).

The SCS system is very good, and you can install it on an older model without a stock speed signal by using the coil wires for the signal (although the system will technically maintain RMPs rather than speed per se).

Olivier

Tony911Z · Tony911Z's Garage

PCA's Up-Fixin der Porsche Volume VII contains an article about installing an aftermarket (Dana Corp) cruise control kit and mating it to the factory switch. The article describes making brackets and installing the components into an '82 SC.

RoninLB · 09-01-2003, 10:04 AM

Oliver... thanks for the info.......Ron