Sunday, June 27, 2010

Intermittently working Air Conditioning of Jeep Grand Cherokee 2001

My Jeep A/C has been working intermittently for a couple of years without a  diagnosis. I could live with it but my wife who gave birth to my new baby girl cannot tolerate it anymore.

The symptoms of my A/C are as following:

When it works, everything is fine. Otherwise, the LED of the A/C switch does not light up and there is no cold air either. Sometimes tuning the ventilation knob could let the A/C work but cannot cure the problem.

I googled a lot but didn't find any write-ups on  Jeep WJ with these symptoms. Many Jeep owners had faulty blower motor/blower motor resistor/blend door actuator. My reasoning on my faulty A/C is very simple: Now that it could work intermittently, the major components such as compressor/condenser/ accumulator and blower motor have very low possibility of malfunction. It might be some bad switches, connectors or other electrical components.

I checked the blower motor resistor which is  easy to access but it turns out to be good. (Actually my A/C doesn't work at HIGH when it cannot work normally, but in this case the blower motor resistor is bypassed by the A/C system. So  it is quite reasonable that the blower motor resistor is not the culprit.)

The next target is the blend door actuator. I am not sure if a bad blend door actuator could result in the failure of the A/C. I took it down from the left side of the glove box before the passenger seat. (The glove box is very easy to be removed. Just use some firm force to spin the bin downward. Don't be afraid. It wont break. :-))

I could spin the small motor of the blend door actuator which sounds no problem. The safest way to check is to use a 12v battery to check if the motor can work.

My third step is to check the Heather and air conditioner control panel.

0. Disconnect the battery. 

a: Gently pry each of the four corners of the center lower/upper bezel away from the instrument  panel. A used dinner knife would serve this purpose well. 

 Upper bezel:
 Lower bezel:
 b. Unscrew the bolts at four corners of the Heather and air conditioner control panel then the panel is down.

c. Hook on the battery and test the fan switch at the left side. The voltages  between the four pins are symmetric ( the approximate readings in my  memory are 12.37 v/ ~0.25 V ). I forgot to take the picture of these pins.  Then  it sounds that the biggest suspect is  the  following vacuum switch at the back of the heather and air conditioner control panel. 

d. To confirm that the vacuum switch is faulty, we start the engine and push connector to see if the A/C or electrical fan is working. Anyways, if any difference of the symptom happens when we let the connector move without taking it apart. Then we are sure that the connector need service. In  my case the connector was somewhat loose, and the A/C began to work when I firmly pushed the vacuum harness toward the panel. This indicates that the vent vacuum switch is the least culprit of the problem.

e. To service the connector, I have some lessons: First, we should be careful that  there are three springs inside the connector and they would bounce away to nowhere if we pry off the three clips carelessly. So let the vacuum harness lift SLOWLY off the metal axle in the knob.  (If one did miss some springs, the spring in some click ball-point pen is a good alternative.)   Second, mark the relative location of the metal axle in the knob (the intersection of the axle is a half circle) and the vacuum harness.

f. Use some cleaner (I use WD-40) to clean the inside of the connector which is a printed circuit. Note there is a plastic round seat for the three springs  with a metal  cover at half way of the metal axle in the turning knob. Normally, it is impossible to restore the relative position of the springs and their cover because they are not held together by anything, unless the first two owners serviced it and missed something.

I employed my 50 lbs fishing line to hold the springs to their plastic seat with the metal cover. The hard fishing line is the best material that I can imagine  and can do this job. (Sorry, forgot to take pictures. It looks quite funny.)

g. I think, if i am not naive, that the connector of the vacuum harness might need some sort of sealing. So I dripped some ATF on the connector. (The fifth picture shows the oily connector).

h. Hook the connector with  the metal axle in the turning knob.  Note there is a metal bead on top of the plastic seat of the springs. Since the connector is loose.  I used fishing lines again to hold the connector firmly.

I. Reverse the steps that we took down the upper/lower bezels and restore the panel. 

J. Test. It works like a charm for me. Thanks for reading. ;-)


Friday, June 04, 2010


1. Rear Windshield Wiper Motor; 127 CAD

2. Rear window lock actuator; 

3. Power window motor (passenger side);

update: Power window motor (driver side); replaced $38.8. (August 17, 2011)
update 2: ebay part was not durable, ordered from a dealership for both sides (July 14, 2012  $280)

4. Seized front right caliper; 90 CAD

5. Broken CV boot; 90 CAD CV boot broken again ( at 08/2010 120 USD)

6. Lower tie rod end; 90 CAD

7. Fuel pump failure (hard start overnight); 680 CAD

8. Crank position sensor (about 200 CAD)

If P1756 code cannot go off with corrected fluid level, I might have (ALREADY replaced, note in 03/2011) to buy

8. Governor pressure sensor+soleniod (257 CAD + tax at dealership) and  AMSOIL ATF (100 CAD)

9. Water pump (640 USD)

10. All discs and pads (300 CAD)

11. Electric Fan relay (32 USD)

12. E-brake  (400 USD)


E-brake handle ($93 from airpark dodge dealership, AZ, 2012)

13. Brake flush (47 USD)

14. Differential flush ($34)

15. Wiper arm ($76)

16. HAVC control panel ($151)

17. Hood support struts ($46)

18. wheel center caps ($50)

19. Tail lights assembly with sockets ($65+$35=$100)

(updated Jan 2014)

Total as of Jan. 2014 $4342.


Thursday, June 03, 2010

P1756 Jeep Grand cherokee problem

Too bad my Jeep is sick again! P1756: Mid pressure malfunction....Governor sensor/solenoid problem.


Today I checked the transmission fluid level.  It was far too low than normal. Even though I knew the measuring procedure, it is still very annoying and perplexing to read the dipsptick:
One side reading looked ok but the other side was too low.
        Another trouble was that I used Amsoil ATF to flush the tranny and already run  out of it. I had to spend $16 for a single quater in a small auto parts shop. After driving to and forth for almost a whole day, I finally add 1 quater of ATF.

code erased. let's wait and see if it could come again. If it is not the fluid level problem. i had to replace the governor pressure sensor/solenold which will cost more than 260 cad plus tax and extra ATF.

so far so good without replacing anything.