A/C Hi-Lo pressure switches and EATC

[koda2000]

Today while driving my '00 Mountaineer I turned on the A/C (on MAX) and got only warm 'ish air. I checked and the A/C compressor is not kicking on/cycling. I checked the refrig pressure with one of those hand-held pressure gauges and (w/o the compressor running) it registered as just into the LOW range, but I would expect that if the compressor isn't running.

I know how to jump the compressor clutch, but is there a way to jump the HI and LO pressure switches?

The truck has a used EATC unit I bought off eBay last Fall, because the old unit stopped controlling the TEMP actuator. I've read where a circuit board in the EATC can prevent the compressor from running. I don't remember if I ever tested the used EATC for A/C last Fall, as it was already cold out. What is the procedure for running diagnostics on the EATC? Would that indicated a problem with the circuit board?

 

[SoHK_alumni]

Sure! Both the high and low pressure switches are simple on/off types, not pressure transducers.

A bent paper clip works well to test/bypass the switches.

 

[koda2000]

Sure! Both the high and low pressure switches are simple on/off types, not pressure transducers.

A bent paper clip works well to test/bypass the switches.

That's what I figured, but thought someone here would know for sure. My money's on the EATC, or a crack in the circuit board. I'll try swapping the relay(s), jumping the switches and if they seem to be okay I'll reinstall the old EATC unit and see if that gets it to work. If it does, maybe I can make one working unit from the 2 broken ones, or re-solder the circuit board. -Thanks.

BTW: Found this info on the EATC Self-test:
The self-test can be initiated at any time. Normal operation of the system stops when the self-test is activated. To enter the self-test, press the OFF and FLOOR buttons simultaneously and then press the AUTOMATIC button within two seconds. The display will show a pulse tracer going around the center of the display window. The test may run as long as 30 seconds. Record all DTCs displayed. If any DTCs appear during the self-test, follow the diagnostics procedure given under ACTION for each DTC given. If a condition exists but no DTCs appear during the self-test, refer to the Symptom Chart Condition: The EATC System Is Inoperative, Intermittent or Improper Operation. To exit self-test and retain all intermittent DTCs, push the blue (cooler) button. The control will exit self-test, retain all intermittent diagnostic trouble codes and then turn OFF (display blank). To exit self-test and clear all diagnostic trouble codes, press the DEFROST button. The vacuum fluorescent display window will show 888 and all function symbols for one second. Then, the EATC control assembly will turn OFF (display blank) and all DTCs will be cleared. Always exit the self-test before powering the system down (system turned OFF).

 

[CDW6212R]

...

BTW: Found this info on the EATC Self-test:
The self-test can be initiated at any time. Normal operation of the system stops when the self-test is activated. To enter the self-test, press the OFF and FLOOR buttons simultaneously and then press the AUTOMATIC button within two seconds. The display will show a pulse tracer going around the center of the display window. The test may run as long as 30 seconds. Record all DTCs displayed. If any DTCs appear during the self-test, follow the diagnostics procedure given under ACTION for each DTC given. If a condition exists but no DTCs appear during the self-test, refer to the Symptom Chart Condition: The EATC System Is Inoperative, Intermittent or Improper Operation. To exit self-test and retain all intermittent DTCs, push the blue (cooler) button. The control will exit self-test, retain all intermittent diagnostic trouble codes and then turn OFF (display blank). To exit self-test and clear all diagnostic trouble codes, press the DEFROST button. The vacuum fluorescent display window will show 888 and all function symbols for one second. Then, the EATC control assembly will turn OFF (display blank) and all DTCs will be cleared. Always exit the self-test before powering the system down (system turned OFF).

Thanks for posting that. I haven't done any diagnostic testing yet, my Mounty will blow warm air sometimes. I'm fairly sure mine is a broken blend door that likes to be one the hot air side, and it randomly moves to cold. I just bought another 98 Limited, so I now have three EATC's to work with.

 

[429CJ-3X2]

When I bought my '01 ST the a/c wouldn't blow cold, and wouldn't take a charge. When I unplugged one of the pressure switches I found the o-ring that sealed the plug had fallen inside the switch side of the plug and was preventing proper contact. Put the o-ring back where it should be and it's been working fine since.

 

[koda2000]

When I bought my '01 ST the a/c wouldn't blow cold, and wouldn't take a charge. When I unplugged one of the pressure switches I found the o-ring that sealed the plug had fallen inside the switch side of the plug and was preventing proper contact. Put the o-ring back where it should be and it's been working fine since.

When I first bought my '01 ST last June the top of the high pressure switch was no where to be found. The previous owner had apparently broken it off while he changed the #4 spark plug. I later found the wire with the top of the switch stuffed into a hole in the frame. I stuck it back on the lower part of the switch and it's been working fine ever since.

Today I figured out the '00 Mountaineer's compressor does engage, but I think there are 2 issues.

1. The refrigerant is a bit low.
2. The Blend door is either broken, or the blend door actuator is not working, because once the engine is at operating temp I'm getting cool 'ish air on A/C MAX, but hot air if I switch the controls to PNL/FLOOR at an indicated 60 degrees on the EATC panel display.

So, tomorrow I'll remove the blend door actuator and see if it's moving with the TEMP setting and manually shut the blend door. Then I'll add a little refrigerant and see if I can at least get it to blow cold for the Summer.

 

[CDW6212R]

My 98 blend door is malfunctioning such that the actuator will easily move it to the hot side, but will not move it to the cold side. If I ever get any cold air I can keep it cold by using MAX AC and manually adjusting the fan. But any temperature used like a 70 or so will make the actuator move the blend door towards heat, and then it turns warm very quickly. Only luck and occasional slapping the bottom area of the dash has moved my blend door to the cold side. So it's been hard to not use the defrost button in the morning for many years, because that commands heat...

Every vehicle is different, I've just figured out that mine needs a new blend door. Hello dash R&R, or cut the dash.

 

[shucker1]

Every vehicle is different, I've just figured out that mine needs a new blend door. Hello dash R&R, or cut the dash.

I know cutting the dash is the easy way, however, my door is busted as well.

I'm just going to bite the bullet and pull the dash to do it the right way.

I may want to clean my ears out with my Glock when done but..

 

[koda2000]

Every vehicle is different, I've just figured out that mine needs a new blend door. Hello dash R&R, or cut the dash.

I know cutting the dash is the easy way, however, my door is busted as well.

I'm just going to bite the bullet and pull the dash to do it the right way.

I may want to clean my ears out with my Glock when done but..

Well you'd actually cut the heater plenum, but although I usually prefer to do repairs the right way, there's no way I'd R&R the dash.

My issues with this vehicle's HVAC system started when I first bought it. There is little-to-no air directional control (I assumed a bad EATC or vacuum motor, it blows air from everywhere equally regardless of setting). The OE 3 post-style A/C compressor clutch was badly worn out and rattled, so I replaced it. Last Fall the blend door actuator stopped working, but the actuator worked fine in my other Mountaineer. Replaced the EATC unit with a used one and the blend door worked fine for about 4 months, but still little-to-no air directional control (I suspect the air directional issue is that the vacuum motor near gas pedal doesn't work). 4 months after replacing the EATC the blend door, or it's actuator, started clunking continuously, so I set the temp to 78 degrees for the winter and unplugged the actuator. Now that I want to turn off the heat it's acting like the blend door is broken or the actuator is no longer working (no clunking even when plugged in and no blend door control).

After I remove the actuator this time, I'm just gonna close the blend door manually and lock it down for the Summer. I might replace the blend door in the Fall if I've got nothing better to do.

 

[koda2000]

Update:
It's starting to get pretty hot down here and GA so I needed to get the A/C working. Today I removed the blend door actuator (That rear bolt is a major PITA, but I knew that going into the job). I then tested the actuator and found it was not moving. That explains why the heat was always on full blast. I found the blend door was still in one piece, so I took the actuator apart and removed the crescent gear that moves the blend door. I reinstalled the gear on the blend door and found it easy to move the blend door from open to closed, however the least amount of movement with the fan on high slammed the door open again. I took an old fuel pump rubber isolator and found it to be the just the right diameter to wedge behind the gear. I then glued the rubber to the top of the heater plenum with a few dabs of weather stripping adhesive to make sure it couldn't come off.

After getting the truck up to normal operating temp and setting the HVAC to A/C MAX I'm getting nice cold air again. I think it can still use a bit more refrigerant, but measured at the center panel vents I'm seeing temps around 40-42 F on A/C MAX with the fan set at about 3/4 speed. I'll see what my daughter things about it.

I'm not going to worry about replacing the blend door actuator/motor until November 'ish. Has anyone found a good source for the EATC blend door actuator for a Gen II? Searching the internet seems to point you at the manual HVAC controls actuator or actuators that don't look like what I took out.