New Sanden SDH715 Not Pumping But Clutch IS Engaged

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scowman
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New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by scowman »

1995 Ferrari 456GT with a brand new Sanden SD7H15 (stock replacement). There is nothing special about a Ferrari AC system as it runs with off the shelf parts from major manufactures. It has an expansion valve/drier and not an orifice tube. The system calls for about 43 oz (1300grams) of refrigerant.

I broke the system apart, flushed with mineral spirits until clear, then immediately followed with alcohol, then air until nothing came out. The old oil was a nice nut brown color, no black or parts of compressor. I flushed both ways through the condenser and evap and the hoses. I replaced the drier but not the expansion valve as access is typical Ferrari (pull the dash !!!).

Sanden install instructions say add no oil for systems with less than 4lbs of refrigerant so I added no oil.

I ran a vacuum -30 overnight and it held all day.

I added one 12 oz can of straight R134a to the high side (engine off).

Prior to starting, the low side/high side were in equilibrium a 80 psi (65 degrees outside).

I started the car, engaged the AC. The AC Clutch engages and the face is clearly spinning with the ac on.

The high side rises to about 200psi then drops below 100 when the fan engages.

THE LOW SIDE DOES NOT MOVE. IT STAYS AT 80 psi!

When I shut off, both return to 80/80 equilibrium>

I am at a loss but I would say the compressor is not sucking/blowing. Other ideas? Have you seen a bad compressor out of the box?

Thanks in advance
tbirdtbird
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by tbirdtbird »

Your low side hose fitting is not properly connecting to the low side piping.
The schrader is not depressing.
Some of the cheaper 134 adapters are not made to the correct tolerance. I would get a better set such as Robinair

Some of your procedures do not follow what we would advise.
We would drain the oil in the comp fully and install our own, that way we know it is the correct oil and the correct amount.
Flushing can be a problem. You must get ALL residues out. There is commercial flush available from Tim, the site owner here at ACKits.com, or flush with naphtha.
We do not prefer mineral spirits or alcohol
You did not say why you replaced the comp. If the old one grenaded, you should also replace the condenser, flushing is not sufficient
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scowman
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by scowman »

Thanks for the help. Just ordered a new Manifold Gauge Set. I will flush with naptha if I start over. Pump is almost 30years old. A $250 replacement seems like a no brainer. I do not think old one cratered. Oil was nut brown and no debris found in flush bucket. System has never worked. Condenser is NLA. I will need to have custom made if that is the issue but is seemed to flush easily enough both ways with only oil coming out.

Thinking more about what you said about connections. Ferrari probably hand-made the connector tubes. They are aluminum. Ferrari is not known for their precision in such items. They build great drive lines and chassis but everything else they make by hand is POS. It could be the the port tolerance rather than the connector tolerance. But I will try a new connector.

Your thoughts are very welcome. I hope I can return the favor some day.
Last edited by JohnHere on Fri Mar 24, 2023 10:16 am, edited 1 time in total.
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by JohnHere »

Over and above the oil and flushing, two things jump out at me. First is the ambient temperature of 65°F, which is too low for A/C work and testing. Second is that you added only one 12-ounce can of refrigerant when the system calls for 43 ounces. So it's obviously grossly undercharged.

I suggest waiting until the daily temperature reaches 80°F or higher, and charge the system to the full amount by weight. Then, proceed with performance testing the system.

Incidentally, did you attempt flushing the evaporator with the TXV still installed?
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scowman
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by scowman »

Thanks for you feedback. Your comments about the can and ambient temp are noted. I did flush the TXV along with the evap. Both ways. This is SOP on older Ferraris as TXV access is a dash pull exercise. Many Ferrari owners have done it with success. But I fear you are going to tell me otherwise :?
scowman
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by scowman »

tbirdtbird:

I slept on your theory that the low side connector was bad. That seems to me to be the most probable case for what I was seeing on the gauges. The 80psi on the low side gauge was from the can, not the system.

From that fact I conclude the following.

1. I did not vacuum the system prior to adding refrigerant. What I vacuumed was the hose lines between the vacuum pump and the low side connector :roll:
2. My system is now full of air/water/12oz 134a :o
3. I need start over with a new drier as the current one if full of water :(

Thanks for the showing me the light switch. I can see clearly now. Hopefully the Robinair gauge set will solve that problem :)
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by JohnHere »

scowman wrote: Thu Mar 23, 2023 5:51 am I did flush the TXV along with the evap. Both ways. This is SOP on older Ferraris as TXV access is a dash pull exercise. Many Ferrari owners have done it with success. But I fear you are going to tell me otherwise
A couple of problems with that procedure: Very little flushing chemical would make it past the restriction of the TXV. So it seems to me that the evaporator, in effect, hasn't been flushed at all. Additionally, if there was any debris in the evaporator, reverse-flushing it with the TXV in place would tend to drive the debris toward the TXV, possibly clogging it. It's also likely that some of the flushing chemical remained in the evaporator, subsequently contaminating both the refrigerant and oil.

I'm sure that tbirdtbird will be back to address your comments that you and he were discussing.
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tbirdtbird
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by tbirdtbird »

John, LOL I do not own any of the conversations here! Please jump in at any time. It so happens I had a lot dumped on my plate today so I am overextended. Feel free to chime in!
Dave
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scowman
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by scowman »

"A couple of problems with that procedure: Very little flushing chemical would make it past the restriction of the TXV. So it seems to me that the evaporator, in effect, hasn't been flushed at all. Additionally, if there was any debris in the evaporator, reverse-flushing it with the TXV in place would tend to drive the debris toward the TXV, possibly clogging it. It's also likely that some of the flushing chemical remained in the evaporator, subsequently contaminating both the refrigerant and oil."

Actually all the flush fluid goes through both directions. I started backwards, then forwards and repeated until the flush came out clear. Then I blew air both ways until dry on a pop test. A lot of Ferrari owners do it this way. Even Ferrari dealers. A dash pull is at least $5k. It involves the removal of the steering wheel and two airbags. So this alternative was developed and tested over time.

This is the TXV. (Link not permitted.)

Thanks again for helping. We will get this sorted. Manifold Gauge Set arrived. I placed it on the low side and got a 50 psi reading so I think that is a good sign. I am going to replace the drier and evacate again. I will run the motor and turn the heater on to increase the ambient temp in the ac system. A V12 throws off a lot of heat...
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Re: New Sanden SDH715 Not Pumping But Clutch IS Engaged

Post by Tim »

Please read the forum rules before I lock or delete the thread.
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