Question about 1993 Jeep Grand Cherokee

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93 jeep grand cruise control suddenly quit working, and the a.c. air only comes out of the defrost vents. Is there a fuse that controls this, and which fuse is it? Thanks

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The symptoms you describe (by now you've fixed this, no doubt) are a severe vacuum leak. if it were a lesser leak, you would get defrost part of the time when you are not pulling a lot of power, or in other words, driving down the road at a steady speed and not trying to pass or accellerate.

the vacuum lines in Jeep Grand Cherokee's are very 'brittle' and 'crack' and the rubber parts 'ionize' and fall apart, or 'leak' from that degradation of the rubber. if you are ingenious, you can disconnect portions of the system (focus on the last line coming off the intake manifold but also check all the lines coming off the intake manifold and even the valve cover breather, as any of these will cause a vacuum leak to occur and do exactly what you are seeing.

Jeep, of course, wants a relative fortune for these cheap rubber parts, but with a bit of ingenuity, you can cobb together the necessary fittings and reducers from other sources, like parts from WEST MARINE (a boat supply outfit) and make your transitions out of nylon, and or brass. Seal everything well with RTV, let it cure, and make sure each 'home made' fitting you build yourself is 'airtight' before you put it on the Jeep.

your vacuum diagram should be on the crossbar just above the radiator, on the right hand side of your jeep as you look into the engine compartment, for your reference. best if you do not take all of it apart, but work with one section at a time.

you'll find your vacuum leak, and then you'll probably have working cruise control and air vents!

good luck!

Posted on Mar 14, 2009

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It seems like a vacuum leak

Posted on Feb 21, 2009


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there are a few things that can inhibit the cruise control on a jeep, and the more prevalent one is a vacuum leak in that circuit (hose) that runs off the intake manifold (rearmost one with the check valve in it), which then jogs over to the passenger side of the vehicle, and takes a dive down under the battery tray to the vacuum reservoir. if you are creative about making a plug after pulling the hose off the intake manifold, and then disconnect the tiny hose from the cruise control actuator, also on the passenger side of the engine compartment, and then pull vacuum either with your mouth or a small vacuum pump, then you've proven that this is not the reason the system is not working. Also, if your valve cover rearmost vacuum line to the intake manifold is 'leaky', it will cause this as well as other issues, such as defroster or air conditioning not to blow thru the air vents into the crew cabin, but only onto the windshield defroster vents. if this turns out not to be the problem, and the hose and valve cover fitting are in good shape (the center section of this is plastic and brittle and subject to cracking and breaking, by the way!), it's a good time to start to suspect the brake pedal switch. this switch has contacts that do more than just allow the brake lights to come on, there are cruise control 'inhibit' contacts in this switch as well. and yes, these do tend to go bad. in any case, if the instrument cluster blue light never comes on, it suggests that the system has more than vacuum problems and this brake pedal switch is most likely the cause if there is no other known electrical problem, such as an open circuit for the cruise control. I wish I could offer more, but the liklihood of the actuator being the root cause of this failure, is pretty slim, and there is not much else for you to play with, though there is probably an Engine Control Module possibility here, as a group of five or six Cruise Control wires actually go into that box. In any case, do the vacuum hose and vacuum checks first, then start to think about the 30 dollar switch on the brake pedal.

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2 Answers

Cruise control has quit working in my 93 jeep grand cherokee.

Most cars operates these devices with vacuum generated by the engine. Start out by checking all you hoses (not cooling system hoses) for vacuum leaks. Be sure to look carefully as some hoses can rub through on the bottom where they rest and you would have to "roll" it over to see it. Don't really believe it is electrical. Some cars use "one way valves" to prevent loss of vacuum so when car is not running, you still have some minor vacuum available. Some cars also have a canister, like a vacuum chamber. Look at all of it.

Good Luck.

Feb 21, 2009 | 1993 Jeep Grand Cherokee

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