bwortman84

I'm new to this forum and I did a search but I have little luck with them and my his history of bad luck has not changed regarding this subject. So go easy on me if there's 5,000 threads regarding my problem.

I bought my 99 Cherokee a little over a year ago because I have always had good luck with them. My family all has them and this one is my third.

The problems, however, started the day after I bought it. It seems the private seller had bandaged things just enough to get my check and not much after that. So before I do any improvements, I need to fix whats broke.

Problem # 1:
My cruise control will not hold speed. I can set is at 55 or 60 and sometimes is will hold 3-5 mph under what I set it for for a few miles but eventually it always seems to just give up. If I'm heading down the interstate (In Idaho the interstate speed limit is 75 mph), it wont even try. I'm worried the ECU is not working correctly.

Problem 2:
It gets hot and humid in the canyon we live in. Today it is 102 in my driveway and 70% humidity. I have two little ones and one is a baby. That jeep is an oven and the AC rarely works. Sometimes it works just fine for a while but then the air stops flowing and it starts making a hissing noise like there is a blockage in the vents. Sometimes it blows plenty of air but the air is hotter than it is outside! My old man and I charged the A/C system but it didn't take much. when the A/C is on, I get frost in the plumbing of the A/C in the engine bay so I know the system is working. I believe it is a problem with the valve system the controls the air coming into the cab.

Honestly, the cruise control thing is a luxury and to a certain extent, the A/C is too. But having to take long trips in the summer with 100 degree air blowing in the windows in my baby's face is not fun. I really need to get this figured out. To add to the problem, someone fraudulently changed my VA compensation information and stole thousands from me so until I can get it back, I'm broke so I need to figure out how to get this fixed without having to pay a shop. I'm very mechanically inclined when it comes to the actual wrench work but my diagnostic skills suck.

Any thoughts?

freegdr

Check vacuum line from cruise to storage ball behind bumper for issues.Is air blowing out of defrost vents
when issue occurs or dash vents .

redjeep1983

I have the same prob on my 99. I found that the vent selector with ac on only acts up with cruise control. I'm also thinking they r related in problem.

freegdr

http://www.jeep4x4center.com/knowledge-base/index.htm

CCKen

freegdr is spot on.

Here's some data that may help troubleshoot the Cruise Control/HVAC problems.

The Cruise Control and AC/Heat systems both operate off of engine vacuum. The source components are in the engine bay.

Here's a diagram of the vacuum tube routing and the vacuum reservoir that freegdr mentioned:



Here's the vacuum tube, white tee off the main tube going to the Vacuum Reservoir, and white check valve as it enters the fire wall to the HVAC Unit:



Here's the tee off to the Cruise Control Servo from the main tube going to the Vacuum Reservoir



Here's how you can check the vacuum system.

I use a hand held brake bleeder pump from Harbor Freight and connect it to the rubber vacuum elbow that hooks to the intake manifold. Simple setup. 1/4" hose connected to the vacuum pump and 1/4"x1/4" hose barb coupling hooked to the elbow.

I removed the engine for the photo op. LOL

Pump the system down to around 15-17 "Hg and see if it holds. If so, the system is good. If the vacuum does not pump up or bleeds down rapidly, the entire engine bay system needs to be inspected.

You can also operate the AC/Heat control panel Mode Selector **** while you have vacuum pumped up/down to hear the valves operating.

There's a check valve at the intake connection. You can remove it and use mouth pressure to suck and blow into the check valve. Naturally, it should alow air passage one way but not the other.

I wouldn't mess with the check valve in the tube that goes into the firewall because that little tube gets brittle and could break if attempts are made to get the valve out.

bwortman84

Freegdr,
I checked and the hose was not connected to the ball. It has not been connected since I bought the Jeep. I have looked at it before and noticed that it was not connected. I am not really sure why I chose not to connect it. I replaced the hose and at this point it is blowing just fine but the air is HOT!

Air does come from the defrost vents when it is set to defrost but when I have the AC on and the blockage occurs, there seems to be no air coming from the defrost vents. I have checked this in the passed.

As for your link, do you have any particular subject you recommend for this concern? I looked through the list and I may be missing something but I cannot find an article pertaining to my particular subject. Or are you recommending this as a general guide? Either way, it seems to be a good collection of information.

Redjeep1983,
I rarely use cruise control because the roads around here are windy so I have noticed no correlation between engaging the cruise control and the A/C not working correctly. While when I do try to run them at the same time periodically, neither functions correctly whether simultaneously engaged ore engaged independently. While this really doesn't mean they are not related, I'm simply providing feedback based on my experience to assist in troubleshooting. Do you believe they could be separate symptoms of the same problem? If so, what are you thinking?

bwortman84

Another note, While the vacuum hose is disconnected, it does pull a lot of air when the engine is running.

bwortman84

CCKen,
Thank you for the advice. I tried what you said and this is what I found.

1. I disconnected the vacuum hose from the intake manifold and hooked my brake bleeder to it and attempted to pump it up... Nothing! Reconnected the vacuum hose to the intake manifold.

2. I disconnected the vacuum hose where it couples with the line going through the firewall. Hooked my bleeder up to the line going through the firewall and pumped it up... Plerrure went up and slowly went down. Most likely due to a mediocre connection between the pump and line.

3. Hooked the bleeder up to the vacuum hose coupler in place of the line that goes through the firewall and pumped it up. Vacuum held until I pulled the bleeder from the vacuum hose. Now this is getting vexing.

4. So I went back to the connection between the intake manifold and the vacuum hose where I could not get vacuum to build up and tried again to find the same result. Additionally, I removed the elbow and connected my brake bleeder directly to the line and still could not get any vacuum to build up.

So anyone have any thoughts based on this? Am I missing something? I will not be surprised if I am...

bwortman84

Update:
Upon further inspection, I found a hole in the vacuum hose between the vacuum reservoir and the speed control servo. A short trip to the friendly neighborhood Napa got me a replacement hose and now I have a good amount of vacuum that holds well as long as I connect the brake bleeder well enough.

I have not had a chance to test the cruise control as of yet but I seem to be getting consistent air flow coinciding with the appropriate control **** setting. However, the air is still hotter than Hell. I checked the A/C condenser and and its as hot as the engine. So I may have remedied one problem only to find another... The story of this Jeep so far... The Napa wont test the system for me for liability reasons and they have no tools to check it in stock. Does anyone have any ideas how I can troubleshoot this new problem?

freegdr

Is compressor kicking in big line should be cold small line hot in regards to ac hoses..

CCKen

It could be the blend air door actuator is not working. In '99 Jeep went to an electric actuator. It's located at the bottom of the HVAC unit in the passenger footwell. near the foot air outlet. If you turn the ignition to RUN, wihout starting the engine, and turn the temp selector back and forth from the hot (red) range to the cold (blue) range while looking up at the bottom of the actuator. You should see the actuator slowly rotate to the appropriate position. Generally, if it doesn't move it's inop. On the other hand, if the actuator is moving the blend door may be broken way from its drive.

Here's a schematic of the system.

bwortman84

Well I think we have a resolution.

Based on all of your recommendations and some research of some previous threads that I was finally successful in searching, I saw another individual having the same A/C problem I was. What ended up happening with him and myself is the clutch on the A/C compressor was not engaging. Well, in my case it was not spinning and I could not figure out why. I got a brass hammer and gave it a few love taps kind of like a stuck starter solenoid and saw some dust and depris fall from in between the compressor clutch and pulley. So I got my air hose and blew it our and you would not believe the crap that came out of it. I started the jeep up and turned the A/C on and it seemed to want to spin so I gave it a few more taps and it started to spin. So While it spun I blew it out with the air hose and it began to engage freely. The air in the cab turned ice cold almost instantaneously! So I took the Jeep for a drive out of town and set the cruise control and it held speed. I got it up to 75 in a straight stretch and it held great for the ten seconds until I had to slow down to make a corner. The A/C blew cold air and the cruise is working like a charm! I can't tell you all how happy I am. Now when I make my monthly 8 hour trip to southern Idaho, if I have my kids with me, life will be nice and posh.

Ultimately, all it took was $1.20 worth of vacuum hose and a few shots with the air compressor. I've been dealing with this for a year and that's all it took! LOL


Thank you all for the troubleshooting tips. They made a world of difference. Now it's on to the next problem...

redjeep1983

I may have to look in that line to the ball again. Let me clarify my previous post. My ac would only act up when cruise is on. I would have cold air but would barely flow. Plus after a while the cruise would start acting up where it seemed to forget its job.

CCKen

Good work.