Another AC problem (did search)

[Ssincere]

Hello there:

I have a 95 escort wagon and today when I was driving I turned the AC. No problem, it worked fine. Then I decided to turn the knob to setting # 4 from setting #3 and the AC just shutoff. Now the AC system doesn’t work. I checked the fuse box (driver side kick panel) and the fuses are good. I checked the fuse box in the engine compartment and the AC fuse is good. Where else can I check? Any ideas? Has anyone experience this before? Thanks

[mightymoose_22]

Clarify the problem a bit...

Does the AC not work, or is the fan not working?

There may be nothing wrong with the AC... it oculd be that the blower motor died or that the switch is bad. Does the blower operate at all?

[Ssincere]

Originally Posted by mightymoose_22

Clarify the problem a bit...

Does the AC not work, or is the fan not working?

There may be nothing wrong with the AC... it oculd be that the blower motor died or that the switch is bad. Does the blower operate at all?

Ok. when you turn the dial you can hear the condensor go on but there is no air coming out of the vents.

[Selectron]

That sounds like it's just a failure in the blower motor circuit. If it's a loose or corroded connector then you might get lucky and find the fault by visual inspection but more likely you'll need to trace the voltage using either a multimeter or a 12V test lamp.

Here are the wiring diagrams for the '95 Escorts, and I'll post again later to suggest some voltage checks:

'95 Escort 1.8L: '95 Escort 1.9L:

[Selectron]

With the ignition switched on and the blower speed selector switch set to Hi, you could start by measuring the voltage directly across the motor terminals - you should have 12V, and if you do then the motor would be suspect. I wouldn't replace it though without first removing it and testing it directly across a 12v source.

If you don't have 12V then connect the meter negative lead to a good ground point and measure the voltage on the motor positive terminal again. If you still don't have 12V then something between the circuit breaker and the motor positive terminal has gone open-circuit, so investigate that path.

If on the other hand you do have 12V then check to see if you also have 12V on the motor negative terminal - if you do then something has gone open-circuit in the ground side of the circuit - that's from the motor negative terminal, through the resistor pack, through the speed selector switch and down to the final ground connection. The point which is open-circuit can be easily identified, because all points above it will read 12v, and all points below it will read 0V.

That's all fairly straightforward but you might also find a situation where you have a voltage of less than 12V on the positive terminal (say 8V, for example) - if so then that indicates a high resistance in the positive feed, where a portion of the 12V supply voltage is being dropped across the resistance (4V in our example, being 12V minus 8V), so in that case look for something like a corroded connector between circuit breaker and motor.

If you find a voltage on the negative terminal which is neither 0V (that's what it should be) nor 12V (that's what you would get if the ground path was open-circuit) then it would indicate a high resistance in the ground path, so once again start tracing through the wiring until you locate the point of high resistance. If for example you found 4V on the motor negative terminal, then all points above the point of the high resistance would read 4V and all points below it would read 0V, so that's how to identify it.

To avoid misleading voltage readings, at all times keep the speed selector switch at the Hi setting, because by design the motor negative terminal will show a voltage reading on the three lower speeds (because of the resistors in the ground path), but the Hi speed setting should always give you 0V.

Finally, there is always the option to switch the ignition off and check those paths using the meter resistance (ohms) range. From the output side of the circuit breaker to the motor positive terminal should be zero ohms, and with the speed selector switch set to Hi, the resistance between the motor negative terminal and ground should be zero ohms. Anything higher than that on either side of the circuit indicates a high resistance which should be located and repaired.

Good luck, and let me know if you don't follow any of that.


P.S. On the wiring diagram, ignore the A/C stuff on the right-hand side of the page; your fault is confined to the circuit on the left - circuit-breaker to motor, to resistor pack, to speed selector switch, to ground.