| Author | Message | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 330 Registered: 5-2002 |
Well that didnt work. Anyone wants copy of temp/pressure chart email me a fax number or i can try to email it to you. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 329 Registered: 5-2002 |
temp. pressure chart.
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| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 311 Registered: 5-2002 |
I'll try to scan and post a temperature pressure chart. | |||
| Jeff 77 GTB (Jbk)
Junior Member Username: Jbk Post Number: 98 Registered: 4-2001 |
Ed, Bruno, Thanks for clarifying the detail on the compressor cycling by temperatute rather than pressure. I was confused by the service manual which mentions the low pressure switch, but not the temperature control. This should make the retrofit easier. | |||
| Kelly J. Vince (Tifosi1)
Member Username: Tifosi1 Post Number: 310 Registered: 2-2002 |
Bruno, Can you post that chart or e-mail it to me. Thx Kelly | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 310 Registered: 5-2002 |
Greg, It goes right underneath it to the side of the pipe. It faces the drivers side of the pipe. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 309 Registered: 5-2002 |
Any insulating tape or foam will work. It will even work with none. The main thing is good clean tight contact between sensing element (capillary tube) from power head (top) of expansion valve and pipe.If connection is loose or not at all valve will seek. This is indicated by low pressure gauge moving up and down with compressor on instead of a fixed reading. High gauge will move slightly also. Wrap insualtion around a good connection and it will be ok. Also you can wrap entire valve and insulate all bare pipes and hoses if you want to. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 308 Registered: 5-2002 |
Kelly, The static pressure on the freon in your system will vary greatly by ambient temp. It could read 50 psi on 60 degree day and 80psi on 90 degree day. (these are numbers out of air. need temp pressure chart to tell you what they are exactly). r134 is suppose to be an exact (dump in) replacement for r-12. It seems like existing tx valve should work fine. I am going to have to get specs for existing valve to resolve the issue's around tx valves,r-12,r134 etc. Anybody know the btu rating on the stock compressor.??? | |||
| Edward Gault (Irfgt)
Intermediate Member Username: Irfgt Post Number: 1626 Registered: 2-2001 |
T.Rutlands has ones calibrated for 134. | |||
| Kelly J. Vince (Tifosi1)
Member Username: Tifosi1 Post Number: 308 Registered: 2-2002 |
Below is the expansion valve I used. I found it at O'Reily Auto Parts for $25.00 Expansion valve Murray Climate Control PART# MRY 38683 THP AC3801C UPC 9636138683 The picture below is correct. the black rubber tape is really 415, but I founds a similar insulating tape at home depot on a roll Aluminum backing for much less. I do have a question for you guys. Since I have converted to 134a. I know it is low when the equalized presure is around 65. At idle it will be 25 and go donw to 10 when at 4,000 RPM. I usually add another can then. It takes about 3 to 4 months to leak down to that level. Question, I know the expasnion valve I have is for R12. I was thinking of taking it back off and asking them if they had one for 134A. Do you think id would make a difference? Right now at 95 degrees in the sun I am lucky to get 60 degrees at the vent. Im'sweating my butt off. Thanks for the help Kelly | |||
| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 411 Registered: 3-2001 |
Thanks for the pic Bruno. It appears to be a single tube exp. valve correct? Does the cap. tube connect to the outlet of the evap. where the suction line comes in from the compressor or does it connect right underneath the exp. valve? When I removed mine it was connected right underneath the exp. valve but I would think it would want to see the temp on the outlet of the evap. Thanks Again for the pic. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 302 Registered: 5-2002 |
I suspect the settings on the high low cutout switches will not be effected by using r134. I will look at a temp pressure chart in the office next week (Wednesday) going to shore . I will post if the difference is significant enough to affect operation.Unlikely as they are probably set at low/high extremes.Unit is cycled by temp. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 301 Registered: 5-2002 |
I show a max(high) and a min (low) pressure switch in the schematic for that car.It is only used to cycle the compressor in event of the obvious high or low pressure. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 300 Registered: 5-2002 |
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| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 299 Registered: 5-2002 |
The 1978 tx valve is internally equalized. there are only 2 connections on it inlet and outlet. the inlet is the small one and the outlet is the large. | |||
| Edward Gault (Irfgt)
Intermediate Member Username: Irfgt Post Number: 1619 Registered: 2-2001 |
The 308 Ferrari does not use a low pressure switch to cycle the compressor but uses a thermostatic switch that senses evaporator temperature for freeze up control and should not be affected by 134 refrigerant. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 298 Registered: 5-2002 |
Greg i just opened up my 78gtb. What do u need to know about tx valve etc.I can post pics if necessary. | |||
| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 409 Registered: 3-2001 |
I went to look for a cross-ref. exp. valve today and couldn't find anything. Does anyone know the rating of the stock valve and if it is internal or externally equalized? | |||
| Jeff 77 GTB (Jbk)
Junior Member Username: Jbk Post Number: 97 Registered: 4-2001 |
While we're on this subject, does anyone know of a replacement low pressure switch that is set for 134a refrigerant? The retrofit guide I have says you need to cycle the compressor on at a lower pressure with 134a to get the same cooling performance as with R12. Has anyone made this change? | |||
| phil hooper (Wolftalk)
New member Username: Wolftalk Post Number: 27 Registered: 5-2002 |
sounds like you have a 328 expansion valve. on the '80 308, everything is as you described wrt the four way between the drier and the exp valve. one tap on the 4-way is capped, one goes to the drier, one to the expansion valve, and one to whatever is behind the master cylinder - which I think you are right - it's probably a high pressure switch. the low pressure switch is hanging below the 4-way - so I guess it's a 5-way). the cap tube just clips against the side of the expansion valve next to another sensor that is going through the firewall via the rubber grommet in the center. as usual I don't remember on the 328 expansion valve where the extra tube connects. I was thinking it dumps into the low side. (possibly a high pressure bypass/safety? - I don't recall seeing a high pressure switch - help bruno!). In any case, I don't think you need the extra tube. if the exp valve internally is the same between the 308 and 328 versions, then I guess capping the extra tube would work. what happens if you connect it to the 4-way, which is high side pressure, I have no idea. Seems safest to take the original exp valve in and match it up to a generic replacement. btw, the black, incredibly sticky foam insulation stuff that you wrap around the exp valve is frigette 221-126 (PMG-1). comes in a roll about 8x what you need, but it's reasonably cheap at around $15 and you can probably retread your tires with the extra :-) | |||
| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 407 Registered: 3-2001 |
I got the valve from another member that has it installed on his car. I too think I may need a single tube valve but this one may work just fine but it depends on a few things. Also since the system has not been in use for sometime I do worry about the switch, etc. | |||
| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 406 Registered: 3-2001 |
Thanks for the info. Actually I am not worried about the threaded connections. This is the old expansion valve and the capillary tube I am refering to is the line with the curly tip. My new valve has this line and an equalizing line that has a small connection on it that would fit on the 4 way next to the drier. I found out what the box does behind the master cyl. It is a pressure switch but has the equal. tube that feeds to the 4 pass con. before the drier. I am wondering what to do for the expan. valve. Should I leave this switch connected and purchase a single tube valve or use my two tube valve and bypass the switch. I believe the switch takes the ground away from the compressor if the pressure gets too high and thus turns the compressor off. This is why I am a little hesistant of removing this unit. Thanks for the info. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 287 Registered: 5-2002 |
If that is the old valve can you post a picture of the new. It sounds like you got the wrong valve. | |||
| Bruno (Originalsinner)
Member Username: Originalsinner Post Number: 286 Registered: 5-2002 |
Wow you lost me. Is the picture above of the old valve or new??? Are you calling the tiny tube on top the cap tube??? It is the equalizer tube for the power head. It only need be attached to the side of the suction line where it was.The smaller opening is the inlet which is where your liquid line from the condenser and receiver goes in. The outlet side is the larger opening where you connect to the inlet line to the evaporator. Often confused and called the suction line.Suction line only starts at the outlet of the evaporator.Please elaborate. I am sure I can help. | |||
| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 403 Registered: 3-2001 |
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| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 402 Registered: 3-2001 |
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| Greg Rodgers (Joechristmas)
Member Username: Joechristmas Post Number: 401 Registered: 3-2001 |
I am changing my exp. valve on my 78' 308. Mine only has one cap. tube. I purchased one from a part # that a fellow 308 owner gave me and it came with 2 tubes on it, one cap. tube and one suction (equalizing) tube. I found my suction (equalizing) tube on my 308 and it connects to a 4 way connection that connects to my a.c drier. It then goes to a unit behind my master cyl. but I can see where it goes from there and I don't see how it connects to the expansion valve. Should my 308 have a one tune exp. valve or should it have a 2 line exp. valve? Can I just disconnect my suction line and put my new exp. valve on and connect my cap. tube to the evaporator and then connect my suction tube to the 4 connection pass by the drier? Any info would be appreciated. Thanks. |
tep/pressure chart