Cruise control

[HotRodPC]

It's always been my understanding on at least the 85 and later, maybe even earlier, this black box with the gray plug and all the wires is for the cruise control. Then this green plastic box is the converter off of the manual speedo to make a VSS of sorts for the Cruise Control and that's how the cruise control knows to apply vacuum to the servo to either pull or release the throttle to keep the locked speed maintained under any condition, like a heavy wind, climb a hill or whatever the case may be.

You must be registered for see images attach

You must be registered for see images attach

 

[HotRodPC]

When you go up a hill, the engine goes under load, which increases vacuum, and pulls further on the throttle. IN general on carb'd applications.

That's true, but how does it know to quit pulling? Is it really that smart to know when the Vac returns to normal cruising it let's off? It would be a real bitch if your CC was set and all of a sudden you developed a vacuum leak so CC detects a need to pull on the throttle.

 

[HotRodPC]

@RetroC10Sport probably would know this ****.

 

[Jrgunn5150]

That's true, but how does it know to quit pulling? Is it really that smart to know when the Vac returns to normal cruising it let's off? It would be a real bitch if your CC was set and all of a sudden you developed a vacuum leak so CC detects a need to pull on the throttle.

Well it's a diaphragm, so as it sucks harder it pulls back, and going downhill, say, it doesn't suck at all and let's it idle nearly.

The early ones just had a little chain like in a toliet to do it.

Sent from my SM-G935V using Tapatalk

 

[DoubleDingo]

That's true, but how does it know to quit pulling? Is it really that smart to know when the Vac returns to normal cruising it let's off? It would be a real bitch if your CC was set and all of a sudden you developed a vacuum leak so CC detects a need to pull on the throttle.

This happened in my jeep cherokee. I bought it in 2002, went to use the CC, and the darn thing took off. Literally, the throttle was maxed out by the system, and I had to quickly turn it off and hope it turned off, or I would've been behind the wheel off a seemingly possessed vehicle. It turned out to be the VSS was loose, but I tell you what, that'll make you crap your pants having a vehicle do that.

 

[HotRodPC]

Well it's a diaphragm, so as it sucks harder it pulls back, and going downhill, say, it doesn't suck at all and let's it idle nearly.

The early ones just had a little chain like in a toliet to do it.

Sent from my SM-G935V using Tapatalk

Yep, I'm all good with that that. I understand the diaphragm and do remember the terlet chain too usually on 70's models. I'm just wondering how it knows what to do if it doesn't read the speedo or use a VSS signal.

 

[HotRodPC]

This happened in my jeep cherokee. I bought it in 2002, went to use the CC, and the darn thing took off. Literally, the throttle was maxed out by the system, and I had to quickly turn it off and hope it turned off, or I would've been behind the wheel off a seemingly possessed vehicle. It turned out to be the VSS was loose, but I tell you what, that'll make you crap your pants having a vehicle do that.

My bro had a car it happened to too. I'm wanting to say it was Chrysler IIRC. Turn it on, it would just go full throttle and keep pulling. Lucky for him, when he hit the brake pedal it kicked the cruise off and all was OK, but he couldn't use CC cuz it just went full throttle and held it there.

One of my Furd Delivery pick ups for my job... I set the CC. Boogying down the freeway, coming up on stopped traffic due to a wreck. Tapped the brake, it kept pulling, WHOA, WTF, hit the brake again, it kept pulling. I got all over the brake pedal to slow it down, then thought to hit the OFF button on the steering wheel and the stopped it from pulling. Talk about freaked out !!! Told our shop tech dude about it and he told me he was supposed to disconnect the CC on all the trucks. I told him BS, I'm the boss at my store and I'm not going to be treated like some little kid. He argued with me said, the owner of the company wanted CC and AC disabled on all the trucks to save fuel. I told him to call the owner and tell him if he disconnects my ****, I'll hook it back up and if he destroys the stuff so I can't I'll be quitting, and how does he figure CC wastes fuel? That helps mpg. Long story short. I picked my truck up later that day with rotated tires, oil change, new front brakes, and was told he added 1/2 lb of freon and the cruise control problem was burned out brake light bulb. So yeah, if the brake light bulb is burned out on early 90's Furds, your cruise control won't disengage when you tap the brake pedal. Talk about stupid !!! Gooo Furd !!!