Cruse Control

[roper0621]

The cruse control on my 85 911 will not hold the set speed, I've checked every thing on the trouble guide and didn't find a problem. Any suggestions?

[llangston1]

Reach down and pull back on the clutch and brake pedals and see if that helPs. my clutch pedal was not returning cOmpletely and kep disengaging the cruise. when I pull it back out to the stop my cruise works fine. Try something simple like this first.

[porschenut]

If your speed will set but not hold, then it's time to rebuild or replace your cruise module. You can get a used one in unknown condition on ebay or from a dismantler for about $100, or have it rebuilt here - Systems Consulting...Automotive Electronics for about $150.

[rgrimm]

On the other hand, when I went through the checklist on the '84, it indicated an open clutch switch. My wrench said "those never go bad."

He was right...the used "brain" I put in had gone bad. Do you know anyone with a 3.2 who would be so kind as to borrow you their module. They pop in and out easily, and it often seems to be the problem.

[Joe Bob]

Cruse Control, I hear Tom likes handcuffs.....

[Mitch Leland]

I would be sure that all the vacuum lines are tight, that made a big difference on my C.C. It will still fall off a mile or so over a long distance and I have to bump it back to the desired speed. I'm not sure if it needs more tweaking, or it's the nature of the beast...

I just completed a 2,500 mile trip in my car and w/o the C.C. my foot would have gone to sleep. It a great accessory for an old car. It also keeps me honest in speed zones...

[Nick Triesch]

Find another module on ebay. That is what I did and it works perfect. I paid $60.00 for a tested used unit. ($500 from Porsche) My CC did the same thing as yours. Then when you get the cash, send in your old one to get rebuilt at the place others listed. You will have an extra.

[Mitch Leland]

Nick,

Good information... Where is the C.C. module hidden. Is it the black box by the M/C?

Thanks,

[Nick Triesch]

Mitch, on my car, an 85 Carrera, it is in the trunk on the trunk side of the dash. Just behind a cardboard cover that comes easy. The unit is bolted on with two bolts with a simple plug. It is a silver little box and it says VDO on the module. As soon as you take off the cover, you will see it. This change out works on many cars. Nick

[Mitch Leland]

Nick, thanks for the info, I thought it might be the little box next to the master cylinder. Since you had your module rebuilt, does it hold a set speed for an indefinite time? Setting mine it jerks, then over speeds the car slightly, it's also hard to nail a precise speed without playing with it. Is yours smoother than that? However I feel lucky to have a working C.C and I would be lost without it...

[Nick Triesch]

Mitch, After I installed the used tested unit from Ebay the CC worked perfect. Before it would go up to speed, then fall all the way down. With the replaced unit, I set the speed and it holds tight on say 70mph. On my car the unit is silver color box that says VDO. I think most of them look like this. Anyway, you can find one! Nick

[LUFTMAN]

i have a used control unit out of a parts car part no. 412. 205/7/4 made in 1985 do not know if it works i can ship to you to see if it works. only cost me $5.00 by usps. does me no good if it does not work. if works we can make a fair deal later. if it does not work i am only out five bucks. worth it to me to see if it is any good and to help you out. let me know what you want to do. regards tom

[DRACO A5OG]

Originally Posted by Mitch Leland

I would be sure that all the vacuum lines are tight, that made a big difference on my C.C. It will still fall off a mile or so over a long distance and I have to bump it back to the desired speed. I'm not sure if it needs more tweaking, or it's the nature of the beast...

I just completed a 2,500 mile trip in my car and w/o the C.C. my foot would have gone to sleep. It a great accessory for an old car. It also keeps me honest in speed zones...

+1, check the vacuum line at the "T" upto behind the Servo. There are two hoses on top of the Servo, the larger one is the Breather and it vents out to the atmosphere. The smaller one is connected to the Vacuum at the "T" to the intake manifold assembly.

My wrench forgot to connect it and when I left the shop my cruise would not set. I went to a gas station to fill up and found the top connection was off. Reconnected and all is well.

I too have a bit of drop off from set but no big deal. I just set it about 3 MPH faster than where I want it.

[Brorag]

you'll go through all the tears, pain and angst, and ultimately replace the cruise control module. Ask me how I know................

[DRACO A5OG]

On my 85:



The rubber (unclothed) is the vacuum line that sets the speed on the CC. Clothed hose is just a vent. Also insure the connector is fully seated and the cable at the Throttle Body is not tight, there should be 1MM slack.

Jim

P.S. see that thicker rubber hose just to the right of the "T", I found mine had a crack right down the middle of it. Replaced after engine drop.

[roper0621]

Hi Guys:
Checked and found the vacuum lines were not tight, didn't solve the problem. Shipped the control unit to Auto & Truck Electronics, 423 921 9085. Cost of repair was $103 includes shipping. The cruse control works great. Thanks for your help
Wayne
.

[Goodie]

On an '80 SC, I get zero response from CC stalk (on the steering column). Where do I start?
I do know all vac lines are correct and tight, as is the electrical connector at the control unit.
Is there a dedicated fuse for the CC?
As always, thanks in avance for all of the great advice!