So at 83F ambient temp and 1500 rpm I see 7 psi on low side and 250 on high. I got one of those vent thermometers and it shows 35F at the vent. Sounds pretty good to me Or should I add a bit more 134? -----Original Message----- From: Pantdino <pantdino@aol.com> To: jeffcobb1 <jeffcobb1@me.com>; detomaso <detomaso@detomasolist.com> Sent: Sat, Aug 6, 2016 12:23 pm Subject: Re: [DeTomaso] use sight glass in AC that has been retrofitted to 134a? Jeff, I hooked up the high pressure side gauge and get these numbers: before starting car, 100 psi both sides after system settles down, at 1500 rpm, low side 7 psi, high side 225 psi. As the car warmed the engine speed increased to maybe 1750 rpm and the high side was creeping up to 240-250 but the low was staying at 5-7. Ambient temp was 77F, so should be about 40-45 low side, 170 high side. According to the info sheet, this "Hi side too high, low side too low" situation would imply "blockage of expansion valve or orifice tube." Would that be from having the R12 valve in a system now using 134? I used my laser thermometer on the vents and got 20-40F, but I suspect that kind of thermometer is not accurate for this application because on my street car I got like 13F, which I think cannot be right. Anyway, it seems to me if I add more 134 I run the risk of blowing the high side hose at 3000 rpm and 85F temp. Does that sound right? I do have 15 12 oz cans of old school R12 I bought way back when, so I could switch to R12, but I would have to take the car to have the 134 recycled, replace the dryer, put the system under vacuum, etc so would like not to. Thank you, Jim -----Original Message----- From: JEFFREY COBB <jeffcobb1@me.com> To: Pantdino <pantdino@aol.com>; detomaso <detomaso@detomasolist.com> Sent: Fri, Aug 5, 2016 3:37 am Subject: Re: [DeTomaso] use sight glass in AC that has been retrofitted to 134a? Jim, All cars use different pressures and for examples this week we did a/c work on a 124 Fiat, many Benz-Bmws-Toyotas, a 71 e-type, Ford +Chevy trucks, a Cobra kit car and a Mangusta. But basic pressures at 1,500 rpm with cooling fans on and on high, with both windows open, rear and front hatch closed, high fan and not on recirc should be about 35 + - low side and 250 + - high. Seems like a 7:1 ratio works the best. Converted systems do need different numbers but never too much of a change. So your low range should vary from 20 to 38 psi and the high 210 to 260 psi as long as above written parameters are meet. The proper pressures will equate to the coolest temps. You have to note that and remember you are just setting the vent output for the coolest temp not some pre-considered ideal temp you hope for. About 30 % of all of our a/c fixes are fixing the stuck on heaters. We are in hot Louisiana, make sure your heater is truly shut off by doing a liquid test. Do use the correct oil and add 2 oz if you are not sure of how much is in. You can always expel the working high side into a cloth or jug for 2 seconds to get an idea if you are oily enough. A lot of spit indicates fine but dry expelled gas needs oil. Keep cool, Jeff Jeff Cobb- I pad W-225-343-7525 C-225-907-4514 Jeff Cobb Auto Works 1316 S. Acadian Thruway Baton Rouge, La. 70806 www.LiveOakConcours.org On Aug 4, 2016, at 11:05 PM, Pantdino <pantdino@aol.com> wrote: Hi, Jeff, What should the pressures be? Thank you, Jim -----Original Message----- From: Jeff Cobb <jeffcobb1@me.com> To: Pantdino <pantdino@aol.com>; detomaso <detomaso@detomasolist.com> Cc: Jeff Cobb <jeffcobb1@me.com> Sent: Thu, Aug 4, 2016 6:55 pm Subject: Re: [DeTomaso] use sight glass in AC that has been retrofitted to 134a? The sight glass is always used as a reference point. You must go by the dual gauges. Never by the low side only. Jeff Cobb On Aug 4, 2016, at 8:44 PM, Pantdino via DeTomaso <detomaso@server.detomasolist.com> wrote:
After switching the AC system to 134a, do you use the sight glass in the dryer or go by the pressure at the low pressure port like with modern cars?
Sorry, but I don't recall what I learned several years ago when I switched the system over.
Jim Oddie _______________________________________________
Detomaso Email List is not managed by POCA Posted emails must not exceed 1.5 Megabytes DeTomaso mailing list DeTomaso@server.detomasolist.com http://server.detomasolist.com/mailman/listinfo/detomaso
To manage your subscription (change email address, unsubscribe, etc.) use the links above.
Members who post to this list grant license to the list to forward any message posted here to all past, current, or future members of the list. They also grant the list owner permission to maintain an archive or approve the archiving of list messages.
After switching the AC system to 134a, do you use the sight glass in the dryer or go by the pressure at the low pressure port like with modern cars?
Sorry, but I don't recall what I learned several years ago when I switched the system over.
Jim Oddie _______________________________________________
Detomaso Email List is not managed by POCA Posted emails must not exceed 1.5 Megabytes DeTomaso mailing list [11]DeTomaso@server.detomasolist.com [12]http://server.detomasolist.com/mailman/listinfo/detomaso
To manage your subscription (change email address, unsubscribe, etc.) use the links above.
Members who post to this list grant license to the list to forward any message posted here to all past, current, or future members of the
So at 83F ambient temp and 1500 rpm I see 7 psi on low side and 250 on high. I got one of those vent thermometers and it shows 35F at the vent. Sounds pretty good to me Or should I add a bit more 134? -----Original Message----- From: Pantdino <pantdino@aol.com> To: jeffcobb1 <jeffcobb1@me.com>; detomaso <detomaso@detomasolist.com> Sent: Sat, Aug 6, 2016 12:23 pm Subject: Re: [DeTomaso] use sight glass in AC that has been retrofitted to 134a? Jeff, I hooked up the high pressure side gauge and get these numbers: before starting car, 100 psi both sides after system settles down, at 1500 rpm, low side 7 psi, high side 225 psi. As the car warmed the engine speed increased to maybe 1750 rpm and the high side was creeping up to 240-250 but the low was staying at 5-7. Ambient temp was 77F, so should be about 40-45 low side, 170 high side. According to the info sheet, this "Hi side too high, low side too low" situation would imply "blockage of expansion valve or orifice tube." Would that be from having the R12 valve in a system now using 134? I used my laser thermometer on the vents and got 20-40F, but I suspect that kind of thermometer is not accurate for this application because on my street car I got like 13F, which I think cannot be right. Anyway, it seems to me if I add more 134 I run the risk of blowing the high side hose at 3000 rpm and 85F temp. Does that sound right? I do have 15 12 oz cans of old school R12 I bought way back when, so I could switch to R12, but I would have to take the car to have the 134 recycled, replace the dryer, put the system under vacuum, etc so would like not to. Thank you, Jim -----Original Message----- From: JEFFREY COBB <[1]jeffcobb1@me.com> To: Pantdino <[2]pantdino@aol.com>; detomaso <[3]detomaso@detomasolist.com> Sent: Fri, Aug 5, 2016 3:37 am Subject: Re: [DeTomaso] use sight glass in AC that has been retrofitted to 134a? Jim, All cars use different pressures and for examples this week we did a/c work on a 124 Fiat, many Benz-Bmws-Toyotas, a 71 e-type, Ford +Chevy trucks, a Cobra kit car and a Mangusta. But basic pressures at 1,500 rpm with cooling fans on and on high, with both windows open, rear and front hatch closed, high fan and not on recirc should be about 35 + - low side and 250 + - high. Seems like a 7:1 ratio works the best. Converted systems do need different numbers but never too much of a change. So your low range should vary from 20 to 38 psi and the high 210 to 260 psi as long as above written parameters are meet. The proper pressures will equate to the coolest temps. You have to note that and remember you are just setting the vent output for the coolest temp not some pre-considered ideal temp you hope for. About 30 % of all of our a/c fixes are fixing the stuck on heaters. We are in hot Louisiana, make sure your heater is truly shut off by doing a liquid test. Do use the correct oil and add 2 oz if you are not sure of how much is in. You can always expel the working high side into a cloth or jug for 2 seconds to get an idea if you are oily enough. A lot of spit indicates fine but dry expelled gas needs oil. Keep cool, Jeff Jeff Cobb- I pad W-225-343-7525 C-225-907-4514 Jeff Cobb Auto Works 1316 S. Acadian Thruway Baton Rouge, La. 70806 [4]www.LiveOakConcours.org On Aug 4, 2016, at 11:05 PM, Pantdino <[5]pantdino@aol.com> wrote: Hi, Jeff, What should the pressures be? Thank you, Jim -----Original Message----- From: Jeff Cobb <[6]jeffcobb1@me.com> To: Pantdino <[7]pantdino@aol.com>; detomaso <[8]detomaso@detomasolist.com> Cc: Jeff Cobb <[9]jeffcobb1@me.com> Sent: Thu, Aug 4, 2016 6:55 pm Subject: Re: [DeTomaso] use sight glass in AC that has been retrofitted to 134a? The sight glass is always used as a reference point. You must go by the dual gauges. Never by the low side only. Jeff Cobb On Aug 4, 2016, at 8:44 PM, Pantdino via DeTomaso <[10]detomaso@server.detomasolist.com> wrote: list. They also grant the list owner permission to maintain an archive or approve the archiving of list messages. References 1. mailto:jeffcobb1@me.com 2. mailto:pantdino@aol.com 3. mailto:detomaso@detomasolist.com 4. http://www.LiveOakConcours.org/ 5. mailto:pantdino@aol.com 6. mailto:jeffcobb1@me.com 7. mailto:pantdino@aol.com 8. mailto:detomaso@detomasolist.com 9. mailto:jeffcobb1@me.com 10. mailto:detomaso@server.detomasolist.com 11. mailto:DeTomaso@server.detomasolist.com 12. http://server.detomasolist.com/mailman/listinfo/detomaso