No Power to AC compressor!!???

I went to the mechanic to recharge my AC but he told me no power is going to the compressor!!

He said he traced it back to the AC controls in the car.

Can I use a AC/Heater deck from an LX bird for my car?? If so I can just go to the junkers and get a replacement.

my car is a 1990 5 speed.

thanks for your answers!!

i dont see why it wouldnt work as long as its coming from the same year bird or close depends on if yours is automatic climate control or the older style

biffteed said:

I went to the mechanic to recharge my AC but he told me no power is going to the compressor!!

He said he traced it back to the AC controls in the car.

Can I use a AC/Heater deck from an LX bird for my car?? If so I can just go to the junkers and get a replacement.

my car is a 1990 5 speed.

thanks for your answers!!

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Save your money and go to a different mechanic who works at an A/C shop.. this one's incompetent. He obviously can't tell you what CCOT stands for and therefore should not be allowed to touch your car.

FYI.. CCOT - Cycling Clutch Orifice Tube. Ford air conditioners are designed to cycle the compressor based on the fluctuation in system pressure. There is a procedure to recharge a low system.

TbirdSCFan said:

Save your money and go to a different mechanic who works at an A/C shop.. this one's incompetent. He obviously can't tell you what CCOT stands for and therefore should not be allowed to touch your car.

FYI.. CCOT - Cycling Clutch Orifice Tube. Ford air conditioners are designed to cycle the compressor based on the fluctuation in system pressure. There is a procedure to recharge a low system.

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I left that part out, I remember him mentioning something about the clutch not engaging or something like that for the compressor. Its my ignorance for lack of knowledge about these things that I let that part out of my original post.

Basically he told me that the unit that controls the AC in the car is not sending any power to the clutch orifice tube and I need to replace this part.

My car doesn't have the auto climate control, I just want to know if I can go to the junkers and grab one from a LX t-bird.

thanks,

Could be the IRCM also, It powers the A/c clutch.

I assume he's also jumping out the pressure switch on the accumulator, because the compressor won't run (or the system charge) if it's got too low. Although I also had a burnt out wire on my climate control panel which caused the same problem (wiring harness was so tight on that unit that the insulation rubbed through against the back of the dash frame) I'd also check the compressor fuse.

Joisey Jim said:

I assume he's also jumping out the pressure switch on the accumulator, because the compressor won't run (or the system charge) if it's got too low. Although I also had a burnt out wire on my climate control panel which caused the same problem (wiring harness was so tight on that unit that the insulation rubbed through against the back of the dash frame) I'd also check the compressor fuse.

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Hmmm... I didn't assume he was jumpering the pressure switch as not everyone would know about that.

Here's the things involved: fuses, control panel, EEC, pressure switch, clutch relay, and finally compressor clutch. Other than light bulbs in it, I've never heard of a control panel going out. At least on the 90 model, there's not much to it; hence there's not a high chance of it breaking.

You can however check it on 4 settings with the pressure switch jumpered to see if it works: Norm A/C, Max A/C, Defrost/Heat, and Defrost will all activate the compressor. Engine running of course.

I'll check the wiring diagrams later to see just which test points should do what.

In the mean time, if you really think the console is the problem, most all Fords of that year should have the same unit. In fact, I see some on eBay all the time.

Hoep this helps.

TbirdSCFan said:

Hmmm... I didn't assume he was jumpering the pressure switch as not everyone would know about that.

Here's the things involved: fuses, control panel, EEC, pressure switch, clutch relay, and finally compressor clutch. Other than light bulbs in it, I've never heard of a control panel going out. At least on the 90 model, there's not much to it; hence there's not a high chance of it breaking.

You can however check it on 4 settings with the pressure switch jumpered to see if it works: Norm A/C, Max A/C, Defrost/Heat, and Defrost will all activate the compressor. Engine running of course.

I'll check the wiring diagrams later to see just which test points should do what.

In the mean time, if you really think the console is the problem, most all Fords of that year should have the same unit. In fact, I see some on eBay all the time.

Hoep this helps.

Click to expand...

Thanks for your response, a wiring diagram would be great to see what kind of test would point out the problem.

i find it unlikely also to be in the control i would bypass the pressure switch with a paperclip on the passenger side back near the firewall on top of the black round thing i think it is the dryer, dont run it to long if your low on freon make sure ac or defrost is turned on

I guess I missed something. Is your system charged or not? The compressor will not come on unless the system is charged first.

XR7 Dave said:

I guess I missed something. Is your system charged or not? The compressor will not come on unless the system is charged first.

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And to get it to charge, you jumper the switch connector on top of the drier with the engine running of course.

OK. As far a wiring, this is from tracing the diagram in the Chiltons manual, walking backwards from the clutch to the controls:

The clutch coil is controlled by the Integrated Relay Control Modle (IRCM) on both sides (12V and ground).

The feed to the IRCM to engage the clutch relay comes from the pressure switch (Pink/Lt Blue wire).

The feed to the pressure switch comes from the A/C control panel. (Lite green/Pink)

When the pressure switch is open (as when there is no pressure in the system due to either a lack of refrigerant, or when system pressure normally cycles low), no signal goes to the IRCM and the relay disengages.

When the pressure switch is closed (like when the system has a normal amount of refrigerant or when system pressure cycles high), the signal goes to the IRCM and the relay engages.

How does the EEC fit in?
The EEC taps directly into the output signal from the pressure switch. When the EEC gets the WOT signal from the TPS, it pulls the signal down low which has the effect of pulling the signal away from the IRCM, thus disengaging the A/C clutch relay. For those wondering about the current draw to the EEC to do this, this is a low power signal.

OK? Everyone get that?

So how do you know whats right? Pull the connector off of the pressure switch and stick a voltmeter into the single wire (lite green/Pink). With the A/C turned on and the key on to the run position, it should read 12V. This tells you the panel switches are working. Then jumper the connector, start the engine, and the clutch should engage. If the clutch does not engage, the problem is either a bad clutch coil or a bad relay in the IRCM.

If the feed is not 12V, then look at the fuses. Everything that moves electrical things has a fuse, in this case check under the dash since its switched by the key.

See if this helps.

It is not necessary to jumper the pressure switch to charge the system. With the engine running and A/C on, simply charge the system and when sufficient pressure is achieved at the switch the clutch will engage. That is why I was asking. If the mechanic was trying to engage the clutch with the engine off, then perhaps that is why it wasn't working if the EEC has control of the compressor it may dissable the compresser unless the car is running. I don't know if this is true or not, however, even if it is there should still be power at the pressure switch as soon as the key and A/C switch are "on".

Thanks for all the info in this post. I just tested my system and i'm now ready to have it charged. Thanks.