I found a thread from a couple of years back, but didn't find more recent info. That earlier thread didn't help much, and I never saw an answer to his problem.

My 05 has the manual transmission, no modifications except Eurocharged magic, and 275/35 rather than 255/35 rear tires.

Last Thursday I had a pair of 275/35 Continental Extreme Contact DWS tires put on (which I like a lot). That was concurrent with the failure, but I can't see how that would cause it, and I've not seen that mentioned as a caution when larger sized tires are used.

Anyway, my symptoms are as described in the earlier thread - I can feel an attempt to engage when I set it, but it quickly releases or immediately fails to engage.

I am getting no lights or warnings, and it otherwise runs wonderfully, as we have learned to expect from these cars.

I've downloaded the FSM but any help from humans with experience would really be appreciated.

Michael
05 Limited Roadster 6spd

 

there's a 5 amp beige fuse for the speed control. I think it's #10 in the block you might want to check if you haven't yet. It could be the problem.

 

I had a problem like that that went away and believe it was a DIRTY set of contacts. EXERCISE IT. Woody Other than that maybe a speed sensor got wacked.

 

Robby, Woody,

Thanks for your help. I found and checked the fuse with a meter, and it is good. I use cruise control any time I can, so it was getting regular use, and the failure seemed all at once. I had noticed what might have been the same thing over the past few weeks, but it was very intermittent, and I assumed it was user error.

Again, thanks. Will post any progress.

Michael

 

Have you thought of the brake switch maladjusted? If that switch is not adjusted correctly, it could be shutting off the cruise control. Just my .02 worth, hope it helps!

 

GraphiteGhost,

I haven't checked. Will pull up the FSM and read through it, and will check brake and clutch pedals tomorrow. Still worried that it relates somehow to the new rear tires, but can't see how the car could know. I suppose some of the sophisticated stability controls could be unhappy.

Thanks for mentioning the switches. I can check the easy stuff.

Michael

 

Did you recently get a brake fluid flush etc?? After having the tires replaced a few months back I had them do a brake fluid flush since I decided it wouldn't be a bad idea...

For whatever reason, for a good week or 2, my cruise control would start, and then stop suddenly, over and over... Not sure if it was a direct result of the fluid flush or because of the tire change. But it seems that your problem may be linked, possibly to the tire change...

sorry!

 

Kolme,

I haven't done anything to the brakes, and made no other changes, except the caps for the bass speakers - I don't think they are the cause.

I've checked the FSM, and find nothing that hints at an issue with a different tire size. Actually there is not much there except a schematic. Will keep looking.

Thanks for the suggestion. I'll post if I find the solution, or what is causing the problem.

Michael

 

Anybody have anything new on this ? Just put on new 285x35x19 Ventus v12 tires on rear & no cruise . Had cruise on 45 mi. trip to shop . Thanks .

 

According to the "tire size calculator" here on the forum, the diameter difference between 255/35's and 285/35's is :
0.83" (3.08%)

I wouldn't think 3% difference would kill the cruise, but who knows ?
Have you looked at the rear wheel speed sensors to make sure the tire place didn't do a boo-boo ?

 

Sounds tire size related to me. How about a master reset. Disconnect the battery.

On post indicates the problem went away after a week or two. Time for the computer to accept the change as normal or ok.

 

My cruise still works and I have the larger tire size. Up front 235/40/18, rear 285/35/19.

 

Off subject, sorry :
Bill, how did you manage to end up in 'Nam at age 17 ?

 

Deleted................

 

Your math is wrong, I was 20, I joined the Navy at 17, born in 1947.

 

Rekon so. Thanks for correcting me, and for your service.
I joined the Air Force that same year ( 1964 ) at age 20.

 

Thanks for yours!

 

Ok , checked fuse , good. Removed negative cable & reinstalled , still no cruise . Battery good , checked with load cell . Posts clean & new negative cable. Took drive today & cruise worked fine . 285x35x19 new rear tires must have confused sensors/ computer. Took about 75 miles to sort itself out. Love ride & handling with new tire size . Thanks Gimli.

 

It must be the tire size causing this.
My Cruise control didn't work above 40 mph since I bought my Crossfire.
It had the factory size tires. Hancook on the rear and 2 different brands on each front wheel.
Now that I have new Continental tires mounted the cruise control works flawless!

 

Mine had an issue yesterday in the SRT where the cruise control would not come on. I had just replaced the RCM with an upgraded RCM. After I drove and parked it..(for a cold beer) , when I went to leave, the cruise control operated correctly. This was the first and so far only failure of the cruise control that I have noticed. No recent tire work, 141,000 mi. Will report back if more failures occur....peace