I have a question that I haven't found an answer except in the 3 gen forums.

I have a 93 CTD whom's air conditioning became less effective a couple of years ago. R12 is the coolant. Tests show its fully charged and not leaking.

I recently did a complete flush of the cooling system and I was checking thr routing of the hoses that enter the firewall to provide heat in the cab. I've also heard about a "cycling switch" that can go bad. Mine cycles but each cycle takes a minute and I've heard that it should be cycling about every 15-20 seconds. the pressure side of the metal hose gets ice cold.

Also behind the glove box is the control arm that that moves left to right back and forth that connects to the temperature lever on the dash. What exactly does this control arm control? An air flow box or the actual water flow to heater coil?

what do you think I should look for to help in cooling more? the 3rd gen forums show putting a coolant lever inline on the return line from the firewall to the top of the motor blocking hot coolant to the inside of the cab?.. Is that a good idea?

Cycling switch.... where is it located and how hard is it to replace and or purchase? When it goes bad how does that hurt the system in providing cold air?


Just trying to get the air cold for those 100+ degree days.

 

The cycling switch is there to keep the evaporator from freezing up, it shuts off the compressor when the refrigerant leaving the coil gets below freezing. The A/C runs colder if you pull the temperature probe most of the way out of the discharge line or bypass the cycling switch altogether. The only "drawback" is that you can't run the fan on low speed or the evaporator might ice up. Not a problem when it's 100+ out there...

I have mine pulled most of the way out and the compressor rarely cycles off. You want it running if you want cold air.

The slider moves an air blend door.

I think your problem is a heater box full of trash. See the sticky for info on how to clean it out.

 

I'll go throught that Wanna.... can you explain why a heater box full of trash would cause the cooling to be poor? thanks,

 

Because when there is trash in the hvac box it plugs up the evaporator core and dosent let as much air through and limits the cooling capabilities.

 

Where is the cycling switch and the temp probe?

 

Passenger side BEHIND the hood spring on the firewall to the outside of the heater blower cover.
Right where you can see it - but you can't get your hands in there; at least not my mitts

 

how do you back out the temp probe

 

Just pull on it, it will slide out of the tube. Mine has only about 2 inches in the tube. The tube is sealed off from the refrigerant space, even if you pull it all the way out nothing will leak out or be damaged.