A/C and Heater help

[nomad]

Long Story:

 

Last year I repaired the A/C in the car and it blew in the 40*F's all last summer.

Last November I removed the dash and replaced the heater core.

Last January I spun a rod bearing and after 5 months have just got it running again.

 

Today I put the A/C belt on and tested the A/C. All of the foot/face actuators work. When I adjust the climate control all the way down to 65*, the A/C compressor clutch does NOT engage. The temp blowing out of the vents quickly climbs to 160*. Engine temp is at 195* at this time.

 

My questions are:

Is there a bypass valve in the heater core that could be malfunctioning?

Is there a airflow diverter in the HVAC boxes that should be shifting air so it doesn't blow over the heater core, and instead over the A/C (condensor/ evaporator or whatever is under the dash)

 

I have not checked any relays or sensors under the hood at this time, but will begin researching that tonight.

 

Thanks,

[nomad]

Ok. Looked in the FSM. There is a diverter/bypass valave under the dash. It is powered by vacuum and a servo. The vacuum comes from the vacuum canister in the engine bay.

On the TB, there is a row of three nipples and one below that for a vacuum source. Does it matter which vaccum lines go where?

[DzNutz]

The nipple on the bottom is for your HVAC. On the drivers side of the center console (near the gas pedal) is the actuator for the hot water shut off valve. Visually check to see that this is actuating up and down with the temp on the display

 

mine is disconnected in the pics because it does not work, at least I can manually shut heat off and on. The heater shut of is electrically controlled and the connector is a royal pita to get to.

http://i138.photobucket.com/albums/q272/DzG54BNutz/S4020889.jpg

http://i138.photobucket.com/albums/q272/DzG54BNutz/S4020888.jpg

 

If your HVAC is actuating air flow then your vacuum is fine.

http://i138.photobucket.com/albums/q272/DzG54BNutz/S4020887.jpg

http://i138.photobucket.com/albums/q272/DzG54BNutz/S4020886.jpg

http://i138.photobucket.com/albums/q272/DzG54BNutz/S4020885.jpg

http://i138.photobucket.com/albums/q272/DzG54BNutz/S4020884.jpg

Edited June 12, 2011 by DzNutz

[JAinsworth]

Here is some a/c information that mike_c put out a while back:

 

A/C diagnostic connector is a small 2-wire connector hanging under the dash. Generally it's taped to the wiring harness behind the stereo:

* Remove the passenger side "knee panel" (under-dash panel); don't bust the sensor clipped to this panel.

* Remove the carpet/trim panel on the side of the stereo console.

 

Look at the back corner area of that carpet/trim panel for a couple 2-wire connectors - one goes to the sensor on the knee panel; next to is the diagnostic port. It'll have green and black wires.

 

The glove box connector (where the ECU diagnostic port is) also has a pin for the a/c:

PPkkPPP

PPPPPGP

 

"P" is a spot for a pin - may or may not be used, "k" are the two empty spots that "key" the connector, and "G" is the green diagnostic wire.

 

Typical a/c problems:

 

* on the thermostat housing there is a small temp on/off switch; this sensor should read 0 ohms to ground on a cold or warm engine. On an overheating engine it'll read infinite ohms. This sensor fails regularly (infinite ohms) killing the compressor. You can just ground the wire going to it as a test - a yellow+white wire.

 

* Dual pressure switch - one of the sensors in the refrigerant lines near the receiver/dryer. This thing senses too little refrigerant pressure before letting the compressor run (if the "resting" refrigerant pressure is too low the won't be any oil for the compressor; this switch prevents the compressor from running in that condition). It also senses too much pressure and kills the compressor before a/c hoses explode. It's rare for this switch to fail, you can unplug the connector and jumper the wiring harness though to simulate a normal sensor: green+yellow and green+white wires.

 

* Inside the evaporator box (under-dash box that actually cools the air) is a temp sensor that the a/c computer uses to prevent freeze-ups. If this sensor reads too much resistance, the computer thinks the air is colder than it really is and the compressor gets turned off. Look for yellow+blue and red+green wires (coming from the big black plastic box; the connector will be near the diagnostic connector actually), unplug the connector. Using an ohmmeter, measure the sensor resistance: it should read about 1000 ohms on an 86 degree day; about 5000 ohms on a 50 degree day. If the resistance is above 5000 ohms the a/c computer will be thinking "very cold air, don't need the compressor."

 

 

Have you looked for error codes from the a/c computer - it's in a 2-pin connector in the wire bundle near the stereo & passenger knee panel. It's often confused for the knee panel temp sensor connector by the way; it should have a green and a black wire. If the a/c computer is "happy" you'll have a constantly flashing/blinking 12volts-0volts-12volts cycle. Otherwise it'll spit codes.

 

I'd also put a voltmeter on the a/c condensor relay coil wires and see if the computer is trying to turn it on at all... lately I've seen a couple that only spit out 3 volts or so... rather than 12. Bad a/c ECU.

 

Otherwise you've already covered the usual suspects. The a/c ECU, relay, and fuse #7 are about all that is left.

 

A/C compressor is affected by a couple thermoswitches and the pressure switches:

 

* the small 1-prong thermoswitch on the thermostat housing itself is the GROUND for the compressor relay. This temp sensor often goes bad. Easy test: disconnect the wire going to it and ground the wire instead. If the compressor runs properly, the sensor is shot. It's supposed to be an on/off switch - not a variable resistance sensor like the sensor feeding the dash temp gauge. On an engine that is NOT overheating, the sensor prong is shorted to ground (so the compressor relay and compressor work normally). On an overheating engine, the sensor "opens" killing the a/c compressor. Usually this sensor rots internally and NEVER completes the ground (often you can rotate the connector tang when this happens) so the a/c compressor never turns ON at all. A rapidly cycling compressor usually isn't caused by this switch - that'd be a funky failure mode for this switch/sensor.

 

* teeny thermosensor wedged against the evaporator underneath the dash. The a/c computer uses this sensor to monitor the refrigerated air temps; mostly making sure it doesn't get cold enough to start ice formation. Also, when the a/c system is working correctly on AUTO, you'll notice the fan doesn't run at full speed until the air gets cold... this temp sensor feeds the a/c computer that info. To replace this sensor, you have to drain the a/c refrigerant and remove the evaporator box from underneath the dash... not fun. It's resistance CAN be checked though easily; it's a simple two-wire connector coming from the evap box. Unplug the connector and stick an ohmmeter on it. An overcharged system will result in too-cold air temps causing the computer to cycle the compressor more often.

 

* refrigerant "dual pressure switch" that kills the compressor if the refrigerant pressure is too low (no refrigerant or most has leaked out) or too high (about to burst the a/c hoses because of too much refrigerant, problems with the fans on the front of the car, front radiators blocked with dirt/leaves, etc).

 

Typical dash vent temps (center vents) are around 50 to 54 degrees on a working R134a converted StarQuest a/c.

 

mike c.

 

[JAinsworth]

a/c relays from mike c:

 

A/C relays by Mike C

 

The A/C system has a whole slew of relays... those relays on the black metal bracket next to the ignition coil.

One relay for the compressor. (Green+white, Yellow+white, Black+white, and blue+red wires)

One relay trips the larger (primary) radiator fan. (green+white, black, black, blue+white wires)

One relay trips the smaller (secondary) radiator fan. (green+white, black, black, and white wires)

 

Those three relays are driven together/simultaineously by the A/C computer. The green+white wire is the +12volt ON signal from the A/C computer, the smaller black wires are the grounds. The yellow+white wire on the compressor clutch goes to the overheat temp sensor (top of thermostat housing, it's the smaller temp sensor) to get grounded.

 

Another relay (blue+black, black+yellow, black, blue+yellow) trips the front pusher fan if/when the A/C is ON and the refrigerant pressure gets rather high... i.e. hot days.

 

Note these a/c relays are totally different from the relays that the cooling system temp sensors drive (those are the relays underneath the air filter box). So each engine-side fan has two different relays that can run it: the A/C relay OR the cooling system relay.

[ucw458]

There are 2 things I would check first in this situation.

 

1 Do you still have refrgerant? Has it leaked out? Every SQ I've owned had a small leak in the large suction hose that would take months to leak down to the point of non op.

 

2 Does the step motor work? The step motor controls the blend damper and the heater valve. You can see it on the drivers side against the firewall. Run the temp up and down to see if it moves properly.

 

 

 

 

http://i463.photobucket.com/albums/qq352/ucw458/clutch/PIC_0997-1.jpg

[Starfighterpilot]

In addition to what Jimmy posted above, I put together this AC troubleshooting and getting it operational again guide.

 

First of all, if you are going to do ALL of the AC work yourself, you have access to a vacuum pump and an AC manifold gauge set and a refrigerant leak detector. Cuz you will need them to find find out if you have any leaking hose or metal joint connections by pressurizing the AC system; and after you fix any problems drawing a vacuum on the system and pressurizing it with freon.

 

The below are typical problems that make the AC system inoperative provided the AC control panel is lite up and how to correct 'em and get your AC system operational.

 

1] The AC system coolant temperature sensor located at the coolant system thermostat goose neck - Either dirty electrical terminals or the sensor is shot. See FSM Page 24-77 for how to test it. If the sensor is bad and after you correct this problem see if the AC system works.

 

2] AC compressor magnetic clutch - See FSM page 24- 78 for how to test it. The clutch should be tested before you test the below pressure switches. If the clutch does not engage see FSM page 24-99 for the location and how to test it's relay. Make sure that it's relay and electrical connector metal terminals are squeaky clean. Especially check and clean the electic connector metal terminals supplying power to the clutch that's in close proximity to the clutch.

 

3] Dual pressure switch assy - See FSM page 24-77 for how to test it and it's location.

 

4] Pressure switch - FSM says squat about testing this pressure switch - however I have successfully tested it the same way as the dual pressure switch is tested per the FSM page 24-77. See page 24-77 for it's location.

 

5] Leaking AC metal tubing fitting or hose - Now you have to use the AC manifold guage, vacuum pump, leak detector and have your refrigerant at hand. It's required for Steps 5 through 10. If you can not get your hands on 'em you have to take your Lady into an automotive AC shop.

 

5a] If you did not have to replace any of the two pressure switches, hook up the gage manifold and determine if there is any charge left in it IAW FSM page 24-81. If there is you're in luck. Get your leak detector and search IAW FSM page 24-85 & 24-80.

 

5b] If there is no pressure, now is the time to replace any pressure switches that were FUBAR. Then you have to evacuate the system, measure any oil that is pumped out of the system, re-add it back in and then pressurize the system with freon and have a leak detector to perform this test, which is why I said you have to have access to the equipment I noted. If you do, see FSM page 24-80 and 24-83 and 24-84.

 

I have found that the most probable leak location is at the compressor's freon suction hose fitting where it's clamped to the large suction hose. At least that's where my two weeps were when I had to replace that hose cuz of the leaking fitting. And that hose has the chassis mounted hose clamp installed to maintain the hose's position and keep the hose from moving around and stressing that joint. However I think that the engine moving on hard acceleration flexes that joint and consequently wears it out eventually. I have sufficient slack in the hose to compensate for the flex, BUT. That's just my opinion.

 

6] Evacuate the AC system down to zero pressure IAW FSM page 24-82. Repair any leaking metal tubing joint by replacing it's special AC o-ring or replace any leaking hose. See FSM 24-86 for replacing the oring. If the leak is at a hose, take it in to a hose repair shop and have a new refrigerant hose installed using the old fittings. Hose repair shops, such as Pirtek http://www.pirtekusa.com/service/main.asp?gclid=CMvg05zl_qgCFaMQNAodLFd1Rw , can do this. If you replace the entire hose assembly, including new fittings, be prepared for a price shock. Don't forget to install a new oring at the hose fitting ends before you install the replacement hose. Lightly lube the NEW orings that you install correcting weeping joints with some vasoline.

 

8] As long as you have the system depressurized, now is the best time to replace the refrigerent dryer with a new one that's for R-134, cuz that's the type of freon you will probably get to repressurize the AC . Some people say the R-12 dryer will work too, but it's my opinion that you should use the dryer that is specifically designed for the type of refrigerant you are using.

 

9] Now evacuate the system IAW FSM page 24-83 and charge the system a couple of pounds IAW FSM page 24-84 and then check if the fittings that you broke loose are leaking with the leak detector. No leaks great! Continue pressurizing the system IAW FSM 24-84 through 24-85.

 

10] Adjust the AC compressor drive belt IAW FSM 24-87.

 

11] Get in and start up your Lady and you should start feeling that blessed cool air coming out of the dash vents after a while.

 

12] Let your Lady idle for a while and check that the AC condenser pusher fan is cycling on and off as required. If it's not, see FSM page 24-99 for the location of it's relay and how to test said relay. Make sure that the relay and it's electrical connector metal terminals are squeaky clean.

 

13] Check that the radiator primary & secondary fan are running and maintaining engine coolant temp within spec. If any of them are not working then see FSM page 24-99 for the AC radiator fan's relay location and how to test it. Make sure that the relay and it's electrical connector metal terminals are squeaky clean.

 

14] If the radiator fans still do not work, then check the rad fan motor relays electrical connections and test them IAW FSM page 7-15. Keep in mind that the radiator fan relays (fan motors) are also controlled by the AC radiator fan relays when the AC is in operation regardless of engine coolant temp. Now would also be a good time to also check and clean the radiator fan motor ground connections. See FSM page 7-14 for their locations. The ground mounting bolts are special tin coated bolts to ensure a good electrical ground. They have an "E" embossed on the bolt head. Tap the bolt hole threads to remove any corrosion. Coat the contact surfaces with dielectric grease.

 

15] It would also be a good time to disassemble the power harness barrel electrical connectors that supply power to the radiator & AC condensor fan motors IAW http://starquest.i-x.net/viewtopic.php?t=1097&postdays=0&postorder=asc&start=25 the barrel electrical connectors shown in this SOS Manual are very similiar to the rad fan motor electrical harness connectors.

 

16] Clean the male and female metal terminals of the the radiator thermosensors and their electrical connectors IAW http://starquest.i-x.net/viewtopic.php?t=1067&sid=ecc2e9322622d4520f62ac75a4bab696

 

17] Clean & test ALL of your fusible links and their electrical metal terminals, cuz you are now going to be putting a greater electrical load on your Lady's electrical system and the engine house will be hotter cuz of the AC condenser's radiated heat load that will be passing through the radiator, ESPECIALLY WHEN YOU ARE STOPPED DEAD IN TRAFFIC ON A HOT DAY. More heat equals more electrical resistance, which you want to keep to a minimum. I would also clean AT A MINIMUM electrical connector A-33 or 34 depending on the year your Lady was Born. See this link for where it's at in the engine house http://starquest.i-x.net/viewtopic.php?t=1180&sid=faa2c5a4630a31efa04e57856652f1e0 and all of the grounds in the engine house http://starquest.i-x.net/viewtopic.php?t=916. Don't forget to coat the connector's metal terminals with dielectric grease.

 

It would probably be a good idea to have the radiator rodded out NOW if it hasn't been in the past couple of years. Cuz if it's borderline clean now, you will get a high engine temp shut down of the AC system when it's 95 Deg out, and you are sitting stopped dead in rush hour traffic just when you want the AC the most; NOT TO MENTION THE POSSIBILITY OF CRACKING THE ENGINE HEAD.

 

If you get the AC system working without cleaning all of the fan motors, sensors, and relay electrical connections, A-33/34 and grounds, which I mention in my above long winded blurb, you may not still have the AC system working to it's greatest cooling capacity cuz, corrosion in especially the rad & condensor motor circuit, plus A-33/34, could cause the rad and condenser fan motors to not turn at their rated speed.

 

BTW - I intentionally referenced to the '88 FSM so you have to down load and use it.

 

For What It's Worth.

 

KEN

 

PS - Don't take the chance and reuse any old orings that were in the tubing joints, hose fitting ends if a hose was replaced, when you replaced the refrigerant dryer or you had a metal tubing fitting joint weep. They are cheap and it's not worth the trouble of going through the above BS again.

 

PPS - Many guys suggest that you should have the AC system flushed out prior to leak testing. However you have to take your Lady into a Automotive AC shop to have this done. That is your decision to make based upon how deep your pockets are - cuz it ain't cheap if that is the only thing you want them to do.

[ucw458]

Just an FYI because I see the wrong term used alot.

 

"Freon" isn't the correct term. Refrigerant or R134a/R12 is the correct term for vehicles. "Freon" is a Dupont brand name for R22 (used in houses and commercial buildings). Any R22 not made by Dupont is labeled refrigerant.

 

 

Not that it really matters but I'm sure someone will find that info interesting.

[The Rabbit1]

I just put 50psi of air into the lines and let it sit for an hour to check for leaks. no need to put that uv stuff in, it's just taking up space the 134a could be in. hence less 134 in the system.. my thought process anyways. I only use that dye if it definitely has a leak.

[nomad]

Thank you everyone for all the input.

Through your advice I was able to determine that the step motor is weak and didn't have the torque to move the linkage to fully close the bypass. I disconnected the link age and the motor moved fine through out the range of motion when controlled by temperature selection. I moved the linkage back and forth by hand until it moved more easily.

 

After this, I hard wired the compressor clutch to the + of the battery. After 2 minutes, there was no change in cooling. There for I believe that the system is low on refidgerant. If I depress the shrader valve on the compressor I can tell that they is still pressure in the system. So, hopefully I wont have to pull a vaccum on it, but if adding some gas doesnt fix it, I can do that.

[Coke]

Good info. This should be added to the FAQ.