What is it.....?

siminsez01 · #1 (**permalink**) 02-15-2005, 09:30 PM

Got a question about this weird part that is making a ticking noise. It is located in the engine compartment on the passenger side very close to the windshield. It is actually kind of attached to the hood hinge. It has power going to it, and what seems to be 2 hoses(vaccum lines?).

It is making a fairly steady tick, approx 2 per second, that can be easily heard over the sound of the engine.

I disconnected the power to this thing and it tripped the check engine light. So, i reset the computer, reattached power to this thing and started up the jeep. The ticking had stopped, i thought. I gave the engine a good rev and went back to the thing. It was ticking once again.

When i say ticking, i mean that i can put my hand against the part and FEEL the whole thing ticking.

Name that part!

Saurian · #2 (**permalink**) 02-15-2005, 09:41 PM

??? I have NO idea, have never notices anything like that in my '00 where you are describing...

siminsez01 · #3 (**permalink**) 02-15-2005, 10:01 PM

just ran out and took pictures of it

where it is in the engine compartment:
http://www.ionz.net/~bobby/Pictures/Thing1.jpg

close-up
http://www.ionz.net/~bobby/Pictures/Thing2.jpg

Saurian · #4 (**permalink**) 02-16-2005, 06:31 PM

OK, umm... I was thinking the wrong side of the engine compartment... Let me go out and look to see if mine has a counterpart, I might have an idea here...

Saurian · #5 (**permalink**) 02-16-2005, 06:39 PM

I have the same part. There are indeed 2 vacuum lines coming from it, and a wire harness going into the top. The lines seem to creep along the top of the engine compartment, and disappear into the behind-dashboard area somewhere around the engine block. Mine has a little green cap on one of the lines, with a little tag that says EVAP service port... The wire harness going to this is taped into a wire harness that goes on top of the evap canister for the A/C system. My guess would be something related to air conditioning/climate control, a solenoid of some sort... I'll take a look see in the Factory Service Manual to see if I am right.

Saurian · #6 (**permalink**) 02-16-2005, 06:54 PM

It's sharing a wire harness with the A/C Low Pressure Cycling Clutch Switch on the accumulator, but I don't know what it is yet, still looking...

Saurian · #7 (**permalink**) 02-16-2005, 07:12 PM

Allright, sorry for the multi-post... As near as I can tell, this thing is probably, and don't quite me on this, but probably the Vacuum Check Valve... It's designed to keep a steady amount of vacuum in the system in order to keep your climate control steady regardless of engine speed... Climate control is all done by vacuum, heat, cold, vent, floor, all vacuum motors... The faster the engine moves, the more vacuum is being created, if there was nothing to check it, your heating and cooling would change based on the engine RPMs...

According to the FSM, if this is indeed the part, which I assume it is because it shares the wire feed to the A/C accumulator, if it is faulty, or just not working, it cannot be repaired, and must be replaced. I would try AutoZone or somewhere like that first, failing that, check at the Dealership to see if this is indeed the part, but I am about 80% sure of it.

siminsez01 · #8 (**permalink**) 02-17-2005, 08:40 AM

saurian, thanks for all the help.

i had a feeling it had something to do with climate control as it shared the wiring to the AC part. guess i'll have to go by auto zone and see if they have it.

Saurian · #9 (**permalink**) 02-18-2005, 06:26 PM

No worries, sorry I couldn't be more sure of the part, but I am almost positive by description that this is what the creature is, and if so, that's what it's called in the FSM... At least I didn't thingamabob ya to death, I can be bad for that :)

XJNick · #10 (**permalink**) 02-18-2005, 11:53 PM

Hi,

Vacuum check valves don't require electricity to work. I guess it could be an electric vacuum valve which regulates vacuum, but I don't understand why they'd need to have that sort of control over the vacuum to climate controls.

Yes the vacuum fluctuates during acceleration, but that is why you have a vacuum reservoir and multiple check valves; to provide reserve vacuum momentarily whenever manifold vacuum drops too low.

Then again I'm thinking of the type of dampers that are either solid open or closed (as is used in the older Cherokees). This meant that you could either have dash vents, defrost vents, floor vents, or floor and defrost vents blowing air, but NOT any other combonations or blends of air flow. Maybe Jeep got fancy and put in multi-position dampers in the newer Cherokees?

-Nick

Saurian · #11 (**permalink**) 02-19-2005, 12:28 AM

T'is possible, but then again, I could very likely be thinking of the wrong part too... It shares the harness with the switch on the accumulator, and has 2 nice meaty vacuum lines going to it... If I have time, I'll ask around tomorrow...