Need to know what to do on my A/C

[SHOTerror]

I have not been able to get power to my compressor and now today with the EATC unit off the blower continues to blow through the defrost vents. This to me is an obvious indecation that the blower module is shot. The compressor has been recharged and still no cold air, obviously because no power is going to the compressor. Everyone I call to get it checked out once 2 hours of labor just to diagnose, so I have no idea what to do. Any recomendations? Its the '90 BTW

 

[projectSHO89]

The BCM is not the problem of the air blowing through the defrost. This is the failsafe mode when the vacuum motor fails or fails to be operated properly.

Power for the compressor comes via the clutch cycling switch and a relay in the relay module (ICRM) aand more. You will need the schematic and a meter to troubleshoot the electrical fault.

If you don't know how to troubleshoot an electrical circuit, you have three choices: 1) Guess, 2) Pay, or 3) Learn.

If you pick #3, Nook posted a procedure last summer on how he diagnosed his system with no compressor clutch actuation. See if you can dig it up via the SEARCH function.

Steve

 

[SHOTerror]

I have every recept on this car and in 1994 the original owner whom I bought the car from had the A/C diagnosed at Tuttle Click Ford in Irvine, CA. The tech with 170 Labor Hours of experience wrote that it needed AC Clutch, Field Pulley, also rings. Now I would say BS because it is a Ford Dealership but, the tech had 170 lab hours and if they just wanted to screw me he could have just quoted for a new compressor. These items above would they cause symptoms of what I am experiencing?

 

[rangerj]

SHOTERROR,

If the A/C system has 20 to 30 PSI, i.e. enough to overcome the low pressure switch, then power should get to the compressor coil.

Unplug the low pressure switch and jump the switch with a jumper wire. The switch is on top of the filter dryer (aka accumulator).

Look at a schematic of the A/C components in a reference source, such as Helm, Mitchels, Motor, Chiltons, etc. (Library if you do not have one)

Check the fuse. Pull the fuse out and take a close look at it. If it is not blown, clean the spades with fine sandpaper and put it back in.

Next do the same to the relay. You can check the voltage at the fuse box with a volt meter. Then check the fuse with a continuity test.

You can apply direct battery power to the compressor coil (Jumper wires)and listen for the two clutch faces to "click" together.

The coil is an electromagnet, if your not sure about the clutch faces, see if the coil will grab onto anything made of ferrous metal (steel) when activated!

You can either work your way from the compressor back, until you find battery voltage, or if you get battery voltage at the fuse box, work from there towards the compressor.

Check continuity from one connection to the next until you find the break, poor connection, bad low pressure switch, blown fuse, failed relay, or possibly a bad A/C coil.

To do all this you will need the schematic, as suggested by Steve. When you are done doing all this, unless you get lucky and find the problem right away, you will know why the dealer wants so much for a diagnostic fee.

Tools: Multimeter to check Volts, Ohms (resistance), Amps, and continuity, from Sears, Radio Shack, Auto Zone, etc. About $20 to $35.

Jumper wires - make up a set from 14 guage or 16 guage wire souldered to a couple of nails (probes), or alligator clips (Radio Shack). Radio Shack sells a set with the alligator clips already attached at both ends.

A car battery is low voltage, 12 to 14 (approx), but a fully charged battery has enough amps to get your attention. Before you jump any connection, make sure you have the right one.

The best diagnostic tool you have is between your ears. If you learn to use it you can do anything. Let us know what you find! thumbs_u rangerj

 

[SHOTerror]

Yes, I did these test as you recommended when we talked last. I found the fuse was bad at the box (fuse #17) replaced that and still no go, no power to the coil, no power to the evapurator. Not sure where my power issue is, but i'm guessing it has somthing to do with the fact the air blows out of the defrost when the unit is off and won't stop until I pull the 30 amp fuse for the blower.

 

[rangerj]

SHOTerror,

When a fuse blows there is usually a reason, such as a short. That having been said, the fact that you have to pull the fuse for the blower motor to get it to stop running tells me that a relay or switch has stuck in the contact position. (the points in the relay get welded together)

I'm not where I can access my referrence materials, so look on the fuse box cover and see if there is a relay for the blower motor.

If it is not in the fuze box, check the wiring diagrams for the relay. (I cannot remember where that one is, if there is one in this circuit)

If I understand you correctly, a dealer mechanic diagnosed your clutch coil as needing replaced, is that correct? Again, you can activate it with direct battery voltage and see if it turns into a magnet.

The gap between the face and the pulley clutch surfaces should be about .035. If the gap is too large the coil will not pull the face to the pulley. If it does not, it is bad.

The clutch coil, pulley, and clutch face come as a unit. You do not have to evacuate the A/C system to replace them. The process is deliniated in numerous prior posts. 1 wire connection, 1 nut or bolt, 2 snap rings. (Not as easy as it sounds, but not too bad either)

If there is no power to the coil, you must have a short or an open in the path between the power supply and the coil. It can be a switch, a fuse, a relay(I cannot remember a relay in this circuit), a bad ground, a shorted wire, or a broken wire or connection.

Start doing continuity tests on each section of wiring in the A/C system. This is why dealerships, and other shops, charge by the hour to do electrical work! Don't give up, you can do this. rangerj

 

[rangerj]

SHOTerror,

When a fuse blows there is usually a reason, such as a short. That having been said, the fact that you have to pull the fuse for the blower motor to get it to stop running tells me that a relay or switch has stuck in the contact position. (the points in the relay get welded together)

I'm not where I can access my referrence materials, so look on the fuse box cover and see if there is a relay for the blower motor.

If it is not in the fuze box, check the wiring diagrams for the relay. (I cannot remember where that one is, if there is one in this circuit)

If I understand you correctly, a dealer mechanic diagnosed your clutch coil as needing replaced, is that correct? Again, you can activate it with direct battery voltage and see if it turns into a magnet.

The gap between the face and the pulley clutch surfaces should be about .035. If the gap is too large the coil will not pull the face to the pulley. If it does not, it is bad.

The clutch coil, pulley, and clutch face come as a unit. You do not have to evacuate the A/C system to replace them. The process is deliniated in numerous prior posts. 1 wire connection, 1 nut or bolt, 2 snap rings. (Not as easy as it sounds, but not too bad either)

If there is no power to the coil, you must have a short or an open in the path between the power supply and the coil. It can be a switch, a fuse, a relay(I cannot remember a relay in this circuit), a bad ground, a shorted wire, or a broken wire or connection.

Start doing continuity tests on each section of wiring in the A/C system. This is why dealerships, and other shops, charge by the hour to do electrical work! Don't give up, you can do this. rangerj

 

[SHO_Driver]

Like Rangerj was suggesting, give direct power to the compressor, with the engine running and a/c switch on, etc and see if you get cold air. Then take it from there...if the compressor doesn't turn on the problem is the unit. If it turns on then you need to trace the wiring back to the evac.

 

[Mike Kopstain]

Here is an easy one. There is a pressure switch that won't engage the clutch unless there is enough pressure in the system. When I refill my system I usually have to jump this switch to get the compressor to engage.

It's the best guess I got. I'm not an A/C guy.

 

[89 black SHO mtx]

have you run a diagnostic on your climnate control module ??? if the blower stays on when you turn the unit off the problem may be in there!!! just remember you have to turn this on before your a/c will come on automatically so if there is a problem here the a/c will not work unless you jump it manually!!! try running a self diagnostic on the climate control panel. this might hold the answer to which you seek. if not i hope you have alot of paitence and tuff fingers to chase all those wires shrug thumbs_u

 

[SHOTerror]

Okay, I ended up jumping the switch. And no mikey, this wasn't because of your advise I did it before I checked here The air was considerably colder and I could hear the compressor kicking on. So this means one of two things. 1. The switch is bad. 2. The pressure is too low. So, I check the pressure before hand and it read slightly below 15, I hope I checked the right pressure, it is the nozzle by the left head light? Is this lower than it should be?

 

[SHOTerror]

Also, if I get two 12 Oz. bottles of R12 and 4 Oz bottle of oil change for it will this be enough to complete flush and refill the system?

 

[DHMag]

SHOTerror:
Okay, I ended up jumping the switch. And no mikey, this wasn't because of your advise I did it before I checked here The air was considerably colder and I could hear the compressor kicking on. So this means one of two things. 1. The switch is bad. 2. The pressure is too low. So, I check the pressure before hand and it read slightly below 15, I hope I checked the right pressure, it is the nozzle by the left head light? Is this lower than it should be?

left head light ? surely, you mean the RIGHT headlight ? thats the highside fitting. the lowside fitting is at the firewall. always check pressure at the low side. i made a boo-boo and checked the highside once...im still looking for gauge pieces....(high pressure blew the gauge apart).

 

[SHOTerror]

Nope, I ment left side, didn't blow mine to pieces it only read 15, where is it located on the right and what should a correct reading be?

 

[DHMag]

SHOTerror:
Nope, I ment left side, didn't blow mine to pieces it only read 15, where is it located on the right and what should a correct reading be?

shrug all of my A/C plumbing is on the right side of the engine compartment(viewing from the driver seat), left side looking at engine from front. the 89 i pulled parts from was the same way.....might be one of those infamous "dealer installs" ?

 

[projectSHO89]

A complete fill of R-12 will require the quantity specified on your AC system data label which should be under the hood somewhere if it has not been removed or destroyed. Typical amounts are between 2.0 and 2.25 pounds of R-12 for the complete charge.

For a completely dry system, normal oil charge is around 7 oz of oil. You have to completely remove the original oil charge in order to accurately fill the system with its specified oil charge.

The pressure cycling switch is designed to open at around 17-25 psi (adjustable) when the pressure is dropping (compressor running) and should close at 45 psi when the pressure is rising (compressor off). If you measured 15 psi on either service port with the compressor off or on, the R-12 charge is low.

As mentioned, the HIGH pressure port is located next to the radiator cap. The LOW pressure side is located at the firewall, generally above the PS pump. Do not get them mixed up while the system is in operation. If the system has not been engaged for at least 5-10 minutes, the pressures should be equalized and should read the same at either port. This is your system's "static" pressure. The exact static pressure will depend on the state of charge and the ambient temperature, but typically will read somewhere between 50 and 80 psi.

When the compressor clutch engages and the compressor starts running, the LOW side pressure should drop and the HIGH side should rise. You can look for this behavior to see if the compressor is actually compressing. If you read the same pressure on both sides while the clutch is engaged and spinning, either the clutch disk has failed or the internals of the compressor are toast.

Steve

 

[SHOTerror]

I was reffering to looking at it from facing the engine bay so it would be right side from drivers seat, I appologize. I'm going to add one can of 12 oz R-12 this should get me to where I need to be pressure wise... Can I just fill by hooked up to the high side or what would you guys recommend? Do I need some special type of tubing to top off or can I just turn the bottle upside down and stick it on the nozzle?

 

[jasonty]

Wow, I didn't even know they sold R12 anymore. I thought everything was R134a now. Hmm... that's good news for me... R12 is about 3 degrees colder then R134a... wink

 

[SHOTerror]

One word - Ebay! Without ebay many of us would be SOL. Not only do they have it but its damn cheap too. This is my plan: Add 1 can of R-12 to bring up pressure, add it to low side as instructed on can with special adapter to add safely. I am getting all of this off of ebay, wish me luck guys.

<small>[ March 23, 2003, 02:54 PM: Message edited by: SHOTerror ]</small>

 

[rangerj]

SHOTERROR,

DO NOT EVEN THINK ABOUT ADDING REFRIGERANT AT THE HIGH SIDE PORT. Add refrigerant through the low side, always. And yes, one can of R-12 should bring your pressure up enough to switch ON the low pressure switch.

Before waisting the R-12 why don't you fix the source of your leak? Look for a black oily/greasy substance arround connections, spots on the condenser core, or behind the clutch coil
(compressor shaft seal). rangerj