For the people that ask about A/C relay location .....

[Skruyd]

and can't find it.

[93forestpearl]

The relay I'm having trouble with is the one mounted to the evaporator section of hte HVAC system. I can hear it clicking franticly.

[Skruyd]

Do you need a picture of it? I think the whole dash comes out for that one because it's bolted to the firewall..... I think?

[93forestpearl]

No I don't need a picture. It is bolted to the top of the evaporator section and has two wires going to what I suspect is a thermistor, which is stuffed in the evaporator core and held in place by a clip that also goes into the fins of the evaporator. I already have it out of my sedan.

The tricky part will be to put it into my wagon without cracking the system open. The dash must come out, and then the heater core section of the HVAC system so I can access it from that side.

I want the AC to work in my beater car, but I really hate working on it. *sigh*

[tucson_legacy]

I just ordered one, the dealer told me the part # was:

73071AA030 THERMOSTAT CONTROL $52.45

Hope it is the AC Relay.

[91Beater]

The relay I'm having trouble with is the one mounted to the evaporator section of hte HVAC system. I can hear it clicking franticly.

That relay is the round thing mounted on top of the evaporator box on a metal arm. You remove one nut holding the top part of air box and it comes off.

This is the A/C "cut relay" controlled by the ECU.
The one in the hood is the other one controlled by control button, refrigerant switch and evaporator thermo relay.

The HVAC control box with the buttons should be rebuilt by redoing all the solder joints, then if that doesn't fix it, jumper the evaporator thermo switch.

[Legacy777]

This thread is three years old...

[91Beater]

Am I not supposed to add information to it? I personally prefer to use search then simply add on the info rather than to make a duplicate thread covering the same thing from threads no matter the age as its just several threads readers have to go through.

I needed to figure out where that clicking relay was. Had to search it, some commented about it being further up in the dash. I looked in this thread. It wasn't helpful.

i figured it out on my own, and since I know now I thought I'd tack on my findings.

[Legacy777]

Yeah, by all means add information to the thread.


I guess I thought you were just replying to the thread to answer the question from three years ago.

[jp233]

Heh. Yeah, the AC Cut Relay is easy to get to with the glovebox out, one bolt holds the little bracket it's mounted to, and unplug the wire connector.

The evap thermo switch is also easy to get to as it just slides onto a little plastic piece on top of the evap box. However, since the 2 wires run down inside the evap box, it's a pain to replace that switch (easier to splice in a good one, which is what I did but it's still difficult without lifting the whole dash out of the way).

[91Beater]

I haven't completely narrowed down the cause, but mine is fixed.
I first bypassed the evaporator temperature sensor with a jumper. Clicking stopped, but crazy clicking was observed again while removing the switch box(the push button module). It was bad soldering on board.

The relay in fuse box in the hood is controlled by user input as well as sensors.
The relay above the glovebox is controlled by ECU.

Symptoms may not be noticeable at idle as the ECU first raises the idle with ICV before activating AC relay. When idle switch is not in idle position at TPS, engagement is instant.

[Alphius]

What terminals do you jumper on the Evap thermo switch? I need to test if mine is the problem. I have had my A/C only work in hot weather, and it's been getting worse. When I grab the evap switch connecter on top of the airbox and pull on it, the A/C will turn on when it otherwise will not work, so I think that switch is bad. If ambient temps are 75+ the A/C will work just fine. I have verified proper charge with manifold gauges even in cool weather.

What I've read on this board says to connect the L terminal on the car-side harness to ground. Is that correct? I have not examined the wiring diagram in the FSM for this system yet.

[91Beater]

What terminals do you jumper on the Evap thermo switch? I need to test if mine is the problem. I have had my A/C only work in hot weather, and it's been getting worse. When I grab the evap switch connecter on top of the airbox and pull on it, the A/C will turn on when it otherwise will not work, so I think that switch is bad. If ambient temps are 75+ the A/C will work just fine. I have verified proper charge with manifold gauges even in cool weather.

What I've read on this board says to connect the L terminal on the car-side harness to ground. Is that correct? I have not examined the wiring diagram in the FSM for this system yet.

Though not required, this is the easiest way: Disconnect the pressure switch at refrigerant sensor.
Turn the ignition on and probe around for the one that shows +12v against ground at the evap switch.

Jump the OTHER TWO together.

Connect the refrigerant sensor back. The only reason you pulled this is to prevent false +12v from reading on one of the terminals that you jump. I have mine permanently bypassed in this manner and no problem.

If this doesn't fix it, leave the jumper in place and short the jumpered connection to ground. If this fixes it, your problem is in the control box, which is fairly common. You'll have to pull it and redo all the soldering on board. The board is prone to developing joint cracks.

[Alphius]

Mine is a later '94 board that isn't as prone to developing solder problems. That being said, it has been resoldered already in hopes of fixing this exact problem.

I ended up looking at the wiring diagrams and troubleshooting steps in my FSM and identified which wires needed to be jumped together at the Evap Thermo Switch. I made a small jumper connector and bypassed the Evap switch, now my A/C is working perfectly. I haven't had any core icing yet, and vent temps stay well below 40F. Until I have to pull the system apart, I will leave it bypassed. Next time I pull it all apart I will replace that Evap switch.

This seems to be a fairly common problem with the A/C in these cars.