[DeTomaso] use sight glass in AC that has been retrofitted to 134a?
JEFFREY COBB
jeffcobb1 at me.com
Sat Aug 6 20:00:09 EDT 2016
Jim,
You left out if your cabin is cold or not.
Are you vents cold? Your laser seems wrong, stick in a thermometer.
Static 100psi is perfect in ambient 85 deg. Low seems too low which means great compressor and no problem, restriction or bad expansion valve. If cold you at done.
If not cold, then you can find the restriction with a correctly working temp gun. It will show you where a temp change in pipe, hose or condenser happens.
A 134 valve should make a difference if one is made.
True a hose blow is in your future. Stick with 134.
Jeff
Jeff Cobb- I pad
W-225-343-7525
C-225-907-4514
www.LiveOakConcours.org
On Aug 6, 2016, at 2:23 PM, Pantdino <pantdino at aol.com> wrote:
> 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 at me.com>
> To: Pantdino <pantdino at aol.com>; detomaso <detomaso at 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 at aol.com> wrote:
>
> Hi, Jeff,
>
> What should the pressures be?
>
> Thank you,
>
> Jim
>
>
> -----Original Message-----
> From: Jeff Cobb <jeffcobb1 at me.com>
> To: Pantdino <pantdino at aol.com>; detomaso <detomaso at detomasolist.com>
> Cc: Jeff Cobb <jeffcobb1 at 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 at 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 at 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.
>
-------------- next part --------------
Jim,
You left out if your cabin is cold or not.
Are you vents cold? Your laser seems wrong, stick in a thermometer.
Static 100psi is perfect in ambient 85 deg. Low seems too low which
means great compressor and no problem, restriction or bad expansion
valve. If cold you at done.
If not cold, then you can find the restriction with a correctly working
temp gun. It will show you where a temp change in pipe, hose or
condenser happens.
A 134 valve should make a difference if one is made.
True a hose blow is in your future. Stick with 134.
Jeff
Jeff Cobb- I pad
W-225-343-7525
C-225-907-4514
[1]www.LiveOakConcours.org
On Aug 6, 2016, at 2:23 PM, Pantdino <[2]pantdino at aol.com> wrote:
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 <[3]jeffcobb1 at me.com>
To: Pantdino <[4]pantdino at aol.com>; detomaso
<[5]detomaso at 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
[6]www.LiveOakConcours.org
On Aug 4, 2016, at 11:05 PM, Pantdino <[7]pantdino at aol.com> wrote:
Hi, Jeff,
What should the pressures be?
Thank you,
Jim
-----Original Message-----
From: Jeff Cobb <[8]jeffcobb1 at me.com>
To: Pantdino <[9]pantdino at aol.com>; detomaso
<[10]detomaso at detomasolist.com>
Cc: Jeff Cobb <[11]jeffcobb1 at 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
<[12]detomaso at 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
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>
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References
1. http://www.LiveOakConcours.org/
2. mailto:pantdino at aol.com
3. mailto:jeffcobb1 at me.com
4. mailto:pantdino at aol.com
5. mailto:detomaso at detomasolist.com
6. http://www.LiveOakConcours.org/
7. mailto:pantdino at aol.com
8. mailto:jeffcobb1 at me.com
9. mailto:pantdino at aol.com
10. mailto:detomaso at detomasolist.com
11. mailto:jeffcobb1 at me.com
12. mailto:detomaso at server.detomasolist.com
13. mailto:DeTomaso at server.detomasolist.com
14. http://server.detomasolist.com/mailman/listinfo/detomaso
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