Vacuum leak or something else wrong with climate control?

[2001Sport]

Hello all--I've been having problems with the climate control on my 2001 Sport (only 40k). In the past month or two, the controls have only worked intermittently (this includes fan speed, vent controls, and temp). They would stop working, and randomly come back on, usually when it was a really hot day. As of now, in 104 degree Utah, the fan has stopped working completely, though it seems I can still turn the a/c on an off with the middle control. With these problems, I figured a vacuum leak was the issue from what I've read on .

But: I haven't run my jeep in 18 hours, and today I just was starting to inspect some vacuum lines, and found one that has a "T" with a cap in the engine compartment near the battery. When I took off the cap it sucked in a bunch of air--so after sitting overnight it still had plenty vacuum in that line, at least.

Before I drive myself crazy looking for a leak in a line, are there other things I should look at first that these symptoms might point to? (Controls, fuses, the vacuum canister itself?) My oftentimes faulty logic tells me that if there's significant vacuum in that line after sitting overnight, the vacuum system is pretty well holding its own when it comes to leaks. (Unless each line holds it's own pressure??) I picked up this Jeep last year with 30k, and everything looks new under the hood.

Thanks for your thoughts--you guys know your stuff on this site.

 

[RedHeep]

Not sure on 97+, but you shouldn't have fan speed problems with a vacuum leak. The mode controls (vent/heat/defrost) are vacuum controlled, but the fan speed is an electric switch. It would also make sense that the air conditioning is still coming on as that is an electrical connection as well, even though it may blow out the vents if you do have a vacuum leak and the mode isn't switching. Can you be more specific as to what is happening?

 

[2001Sport]

Starting a couple of months ago (as the temp in Utah got warmer?) the controls At first, the climate controls would only respond intermittently to changing them (all three, actually) but then it started shutting the fan off when I'd move the fan control, and later it would "catch up" to me changing the controls. For example, I'd change the fan speed from 3 to 2, and it either the fan wouldn't respond and stay at 3, or it would shut off completely until sometime later when it would come back on. (Most of the time it worked fine.) This would also happen to the vent controls, but that doesn't seem to be a problem right now.

The problem got worse over the last week, and would happen more often and for longer times. Now, the fan is off, and no messing with the control will get it to work. The vacuum line from the canister looks fine, and seems to hold plenty of vacuum.

The middle control is still working fine, I think. I can tell that the a/c compressor kicks in when I turn it to air, and it seems the temp control is working also.

Thanks for any thoughts you have!

 

[2001Sport]

One more update--as I was in stop and go traffic last night, the fan kicked back on. Today I drove twice, and once it wasn't working, and the second time it was on when I started it. When I switched it from 3 to 4, it died for about a second, and then came on full power at speed 4. Should I be looking at the switch itself?

 

[theksmith]

So originally you thought it was all the climate controls messing up... but now it seems only the fan?

I'm guessing it was only the fan all along and the other problems just "seemed" to go along with it untill the fan problem became worse and more evident.

I would say it's either 1-Fan, 2-Switch, or 3-Other wiring in the system.

Sometimes when a fan motor goes out, it's too weak to get itself going, but just the right bump will start it, hence potentially the fan itself. Of course switches are very prone to wearing out as they have physical contacts that repeat the same motion over and over again.

If you are adept at all with electronics, remove the fan switch and manually short the connections to produce each speed, if this all works, then it's the switch, if not, then it's the fan.... or other wires

I don't know how complicated the switch area is, so maybe troubleshoot fan first if it's easier to get to.

Sorry........ It just occured to me that on many vehicles all the climate controls are on a single circuit board that has more of a ribbon cable headed of to the control unit... if so, then troubleshooting the switches might be more work..... How about shotgun maintenence? Junkyard switch panel - try it?

Ok, Now that I've re-read my entire post, I think you should disregard everything as I really haven't been any help at all