C43 Cruise Control- Not Working

**speedybenz** · 07-02-2003, 11:38 AM

Any ideas why my cruise control does not work?

I feel it try to engage, but it will not retain the set speed.

Jeff

**kameraguy** · 07-02-2003, 11:46 AM

I have the exact same problem. I believe it is a faulty relay. As to which one I am not so sure...nor how much they go for. Anyone?

**Eurosport** · 07-02-2003, 12:36 PM

i never use it
but the other night used it for the first time, was a "little" buzzed didn't want to cause too much attention. it worked fine i doubt i'll ever use it again though it's just plain boring.

**kameraguy** · 07-02-2003, 12:49 PM

Originally posted by Eurosport
i never use it
but the other night used it for the first time, was a "little" buzzed didn't want to cause too much attention. it worked fine i doubt i'll ever use it again though it's just plain boring.

Ok.

Now how do we fix the cruise control?

**Brabus** · 07-02-2003, 01:05 PM

What are the symptoms??

So when you try to engage it, does it catch for a second and then once you let go, it lets go??

Can you still use the Cruise control stick to increase speed?

If it fits either of these two, then it's the amplifier box.

**nokia8860** · 07-02-2003, 01:05 PM

Originally posted by kameraguy
Ok.

Now how do we fix the cruise control?

he just said.... just dont use it! hahahha

Ill look to see where the cruise control parts are related on the veh and post what i find.

**Denlasoul** · 07-02-2003, 01:36 PM

Is there a fuse? If so, I'd check that out too.

**Brabus** · 07-02-2003, 02:10 PM

Originally posted by Denlasoul
Is there a fuse? If so, I'd check that out too.

I don't think it's a fuse because he said he can "engage" it. So I'm thinking it's the amplifer if it won't "catch" at speed.

**Eurosport** · 07-02-2003, 03:00 PM

cruise control has different settings
accl set, decc. set, and resume
is it accl set that's not working?
oh and have you removed your steering wheel and airbag recently?

**nokia8860** · 07-02-2003, 04:36 PM

I dont have the names for the parts but here is the harness on how its hooked up. I'll see what else I can find.

**Three Point 6** · 07-02-2003, 05:05 PM

When I changed to a bigger tire on my C36 the cruise did the same thing you guys already are describing! It held for a little and gradually as time kept ticking it would start working a little better. What size are your tires?? If they deviate from stock to much your cruise will not work properly!!!!!!!!

After putting 13,000 miles on my tires the cruise control gradually came back! I did similar posts when mine 'went out' last Fall. A dealer tech told me that the wrong tire choice will screw up your cruise! Just gotta wait for your tires to burn down a little I guess?? I love my autopilot - gives me time to play w/ my radio & yack on the cell!

You guys all seem to be running 18's?? That might be why?
My stock tires were 235/40/17 & I went to a 245/40/17 so the outside diameter grew slightly! I guess if you maintain the correct aspect ratio then you wont have any problems. Peace!

**Rocky** · 07-03-2003, 05:45 AM

Three point is correct.

I had 2 different brands of tires on my stock rims. The car would not engage into cruise control over 120km/hr. Took it to a dealer and they swapped the OEM rims and tires off a showroom C43 onto my car and viola, it worked. I changed the rear tires to match the front and it works again.

**kameraguy** · 07-03-2003, 09:19 AM

Hmmmm....I can't remember if I tried my cruise control before I swapped to 18"....but I know I haven't tried it again after going back to stock.

I will try it later today and see if it works!

Thanks for the info!

**Eurosport** · 07-04-2003, 08:30 PM

mine works after 18's

**mis-u-jerr** · 07-05-2003, 09:30 PM

Originally posted by Three Point 6
When I changed to a bigger tire on my C36

Yeah, that might be it. My service writer said the same thing. Speedy, you're running 255/40/17, right? They are only about 1% biger than stock. However, I think the 235's in front might be a little bigger, maybe the diff is causing it? But I think they are about the same diameter as the 18, so I don't know why more people don't have that problem. Maybe like Eurosport, they never use it? I use my CC all the time, just to keep it under 80

**Denlasoul** · 07-05-2003, 10:49 PM

My cruise control works fine with my car. I am running 18's with 225/40 and 255/35. I believe this setup is fairly close to stock.

**Rocky** · 07-07-2003, 06:19 AM

Fixed yet guys?

**kameraguy** · 07-11-2003, 10:13 AM

Sorry for the late reply guys but I have GOOD news!

My Cruise Control WORKS. I know it sure didn't with my 18" wheels, but it appears there may be a correlation with wheel size. Or at least maybe so in my case. I doubt this is afluke because I tried my Cruise several times when i had 18"s on, and no go. But this morning I remembered this thread and tried it again....it worked perfectly

Wow, thanks for the info guys. Had this thread never been brought up I would have kept on thinking my Cruise was broken. Imma set cruise control all the time now

**Denlasoul** · 07-11-2003, 04:44 PM

What were the tire sizes of the 17, 18, F and R?

**kameraguy** · 07-11-2003, 11:49 PM

When i had 18"s, they were 18x8.5 wheels front and rear, but the tires were still staggered: 225/35 front, BUT my rears were 245/35 rear....the tire shop didn't have the 30 profile in stock....

Now i'm back to total stock...225/45 17x7.5 front, and 245/35 17x8.5 rear.

Could rear wheel diameter affect the Cruise?

**Denlasoul** · 07-12-2003, 10:02 AM

Yes I believe that is the culprit. With significantly different diameters, it probably throws cc sensoring/monitoring out of whack. The wheels are rotating at different rates, probably cc is four-wheel sensored, and it somehow knows that the different turn rates are occurring. It's probably a safety mode.

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