Mystery part, ERP valve?

[Mheiron]

So I’m in Deep on my dash project! Goal is new wiring harness, gauges and AC box. Plus a new brake booster while I’m at it.

Quick question, is this valve required somewhere? I didn’t find one in the original system. If so, where is it located? I bought a NOS piece but have no idea if it’s correct.

Thanks as always for the guidance! Couldn’t get anything done without the forum!

 

[PurpleBeeper]

What car?

 

[davek]

I have never seen one on a 68-70 b body, part number?

 

[1 Wild R/T]

It goes in the suction port of the A/C compressor... It controls the evaporator pressure.... The Expansion valve controls how much freon goes in, the EPR controls how much flows out...

 

[RJRENTON]

So I’m in Deep on my dash project! Goal is new wiring harness, gauges and AC box. Plus a new brake booster while I’m at it.

Quick question, is this valve required somewhere? I didn’t find one in the original system. If so, where is it located? I bought a NOS piece but have no idea if it’s correct.

Thanks as always for the guidance! Couldn’t get anything done without the forum!

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Depends on if you're using the original V2 compressor using R12 refrigerant, then the EPR valveis needed. It controls the suction pressure to a constant value, independent on compressor RPM. If converting using a V2 compressor and R134A refrigerant, remove the EPR valve and then use new thermostatic expansion valve (TXV) compatible with R134A, as R134A has a different specific heat. value than R12 and SHOULD perform better with R134A. Just my opinion.......
BOB RENTON

 

[Daytrepper]

Depends on if you're using the original V2 compressor using R12 refrigerant, then the EPR valveis needed. It controls the suction pressure to a constant value, independent on compressor RPM. If converting using a V2 compressor and R134A refrigerant, remove the EPR valve and then use new thermostatic expansion valve (TXV) compatible with R134A, as R134A has a different specific heat. value than R12 and SHOULD perform better with R134A. Just my opinion.......
BOB RENTON

This, you'll also need to add a thermostatic switch to the evaporator to cut the compressor off so the evap doesn't freeze.

 

[RJRENTON]

This, you'll also need to add a thermostatic switch to the evaporator to cut the compressor off so the evap doesn't freeze.

MOST...but not all older GM systems used the CCOT (Cycling Clutch Orifice Tube) refrigerant control (he orifice tube replaced the TXV) and cycled the compressor Clutch on PRESSURE exiting the evaporator to prevent freezing. Approximately 28 psi off / 38 psi on, or any average of 34 psi using R12 refrigerant to equate ~ 34°F evaporator super heat outlet temp ....depending on air inlet temps and compressor RPMs. Systems changed throughout the years...some used variable displacement V5 Axial flow compressors......each manufacturer had different philosophies........
BOB RENTON

 

[Mheiron]

The car is a ‘69 Charger with factory air which I’m trying to get going again. The car came to me with the AC equipment in the trunk.
I had the compressor rebuilt to run R 134 refrigerant. I had the evaporator rebuilt at classic air and a new condensor.
Any more details on the thermostatic switch and valve would be appreciated.
Thanks for the help.

 

[Mheiron]

I bought a standard exp valve from CI but it doesn’t mention anything about R134 compatibility. How do you determine ok or not?

 

[493 Mike]

The car is a ‘69 Charger with factory air which I’m trying to get going again. The car came to me with the AC equipment in the trunk.
I had the compressor rebuilt to run R 134 refrigerant. I had the evaporator rebuilt at classic air and a new condensor.
Any more details on the thermostatic switch and valve would be appreciated.
Thanks for the help.

I found a adjustable thermostatic switch for my converted 65 Dodge, I believe on the 4 Seasons product online catalog. Just wrapped the capillary tube around the suction tube leaving the evaporator, insulated with sticky A/C tape. Use to cycle the A/C clutch and control evaporator temperature (prevent freezing).
Mike

 

[1 Wild R/T]

I found a adjustable thermostatic switch for my converted 65 Dodge, I believe on the 4 Seasons product online catalog. Just wrapped the capillary tube around the suction tube leaving the evaporator, insulated with sticky A/C tape. Use to cycle the A/C clutch and control evaporator temperature (prevent freezing).
Mike

https://www.amazon.com/Four-Seasons-35845-Mounted-Temperature/dp/B000C2OA20

 

[RJRENTON]

I bought a standard exp valve from CI but it doesn’t mention anything about R134 compatibility. How do you determine ok or not?

The TXV controls the liquid refrigerant inlet (volume of refrigerant) to evaporator, based on the outlet TEMPERATURE of the evaporator, via a sensing capillary/bulb system, acting on the temperature of the exiting refrigerant. The capillary's system gas has the same characteristics as the refrigerant and should be compatible with the refrigerant used. You should CALL and ask the TXV supplier IF the selected valve is compatible with the R134A refrigerant or your equipment supplier. The TXV capillary bulb system is usually mechanically attached (clamped to the evaporator's outlet connection and insulated). Just my opinion......
BOB RENTON

 

[davek]

I converted my 74 challenger to R134 and used all the original pieces just changed o rings and dryer. Cold air and no problems. Maybe 74 did not have it.