1999 Tahoe rear ac and heat actuators

[was3801]

Hello everyone.
My 1999 Tahoe is blowing ambient temperature out of the auxiliary unit on the back. The front works just fine on ac or heat. i have read many posts on this site and others related to my problem. I removed all the trim pieces and the seat belt on the rear passenger side to expose the rear unit. i am looking for the actuator for this unit and can't seem to find it there. Where is it? Does anybody have a picture of location or can tell me where to find it?
Thanks for any tips and help!!

 

[SunlitComet]

IIRC the hoes only had air cooling no heating. that was for the burbs so check your refrigerant tubes in the back and see if one of them gets really hot when the system is running. if so and the other one is just... well... just there then the thermal expansion valve is busted.

 

[was3801]

1999 tahoe rear ac and heat

Thanks SunlitComet!!
I assume the TXV is located inside the rear unit. It will be no problem replacing it...but as far as recharging this unit since i assume it has 2 txv, one for the front and one for the rear, subcooling method may not be as precise as for single txv. Should I charge it by weight? if so do you happen to know the correct amount of 134a for the whole system combined?

 

[SunlitComet]

the front still uses just an orifice tube and the rear is a txv unit that should be mounted on the rear evaporator. your system should start with 2.75 pounds and fine tune it there with a performance test.

 

[was3801]

Thank you sir.
I ordered the TXV and should be in tomorrow. I will take some pictures of the replacement and post them for future reference to others.

 

[SunlitComet]

are you sure that is the issue tho?

 

[was3801]

There is no refrigerant flow through coil. Checked temps at suctions joint by receiver/accumulator, front was cold and rear was ambient temp.
Exposed rear unit and took duct work appart, cheked air temp right after coil and showed 95 F, temp inside of the truck.

 

[SunlitComet]

Just want to make sure that is the issue. Becuase if the rear valve is jammed closed/plugged normally the line that feeds the valve from the front of vehichle is normally hotter then ambient air becuase of the fluid pressure upstream of jammed flow. this is most noticeable when system is turned on for the first few minutes. Sometimes may only be a few degrees too.

 

[was3801]

I tried to send twice a very detail explanation of what I checked and readings but kept on getting kicked out of the forum, I don't know why.
Took temp readings on all the lines including the Y splits and there is no other explanation but the TXV.
I will post all the pictures of the readings and steps to replace the TXV probably Saturday.
Thanks Jonathan.