New Sanden Compressor: High Suction/Low Discharge Pressure?

[Sjohns4]

Followed procedure in FSM which closely matched the Sanden instructions, so I *think* the oil charge is right.
The old compressor didn’t detonate. It just leaked. No sign of debris in hoses or accumulator (replaced accumulator with new).
97 burb with front and rear air. Had both on full, the system would only take just under 2 cans.
With engine at idle and compressor engaged pressures were: 86/130, clutch disengaged: 89 both (high side looked a hair lower, but probably same just scale is difference). To me sounds like either orifice tube isnt working or rear TXV is stuck open? No restriction, just free flow of refrigerant. The tube between the office and evaporator is getting cool, so I’m thinking maybe rear TXV?
Does that make sense or am I maybe missing something else I should be checking?
If it is TXV any tricks to get one unstuck? I was going to replace it for good measure several years ago when I first repaired the AC but didn’t put the new one on because I was afraid of twisting the tube before the threads broke loose.

Thanks,

Mike

 

[1998_K1500_Sub]

Followed procedure in FSM…

You didn’t mention vacuuming the system. Do tell, how did that step go for you?

My ‘98 Sub F/R air takes 4# of R134a.

Year and model info please.

 

[L31MaxExpress]

Make sure the condenser does not have an orifice in the outlet. Second I had the same issue with the 4261 Sanden on my Express van. I put a Four Seasons 10 cylinder HT6 upgrade in its place. Made a drastic improvement. The Sanden barely has enough kick to pull a single evaporator system well.

Did you check the pressures at 2,000 rpm? The high side pressure sounds low even for a 70F day. 2 cans is not half charged. You need to rev it up and put the can of refrigerant in a bucket of warm water. Also this is assuming a proper vacuum was pulled.

 

[1998_K1500_Sub]

Four Seasons 10 cylinder HT6

Have you got a p/n for that compressor or can I simply find it on RockAuto by looking?

(edit) It appears the Four Seasons p/n 88947 is the unit, 210cc displacement/rev, 4.25" pulley diameter. $180 presently on RockAuto.

Compared to Sanden's p/n 4261, 155cc displacement/rev, 4.41" pulley diameter, the Four Seasons 88947 will displace 40% more refrigerant than the Sanden 4261 at the same engine RPM.

Compared to the Sanden p/n 4440, 155cc displacement/rev, 5.12" pulley diameter, the improvement is even more remarkable, 63%.

You need to rev it up and put the can of refrigerant in a bucket of warm water.

^^^ good advice



I’ve got a Sanden 4261 on my Suburban and it works well at road speed, for me anyway; I’ve not needed / used it in temps higher than ~100F.

I would welcome the extra pumping capacity offered by the 10 cyl HT6 at idle / around town.

Those in the southern US would appreciate it even more.

 

[L31MaxExpress]

Have you got a p/n for that compressor or can I simply find it on RockAuto by looking?

(edit) It appears the Four Seasons p/n 88947 is the unit, 210cc displacement/rev, 4.25" pulley diameter. $180 presently on RockAuto.

Compared to Sanden's p/n 4261, 155cc displacement/rev, 4.41" pulley diameter, the Four Seasons 88947 will displace 40% more refrigerant than the Sanden 4261 at the same engine RPM.

Compared to the Sanden p/n 4440, 155cc displacement/rev, 5.12" pulley diameter, the improvement is even more remarkable, 63%.



^^^ good advice



I’ve got a Sanden 4261 on my Suburban and it works well at road speed, for me anyway; I’ve not needed / used it in temps higher than ~100F.

I would welcome the extra pumping capacity offered by the 10 cyl HT6 at idle / around town.

Those in the southern US would appreciate it even more.

88947 is the compressor I have. Still run a 0.062" front orifice tube with it.

Sanden is flat out lying about that compressors suitability to be in a dual evaporator system in the south. The GM HT6 is like 190cc itself.

In ~100F and about 35-40% relative humidity with both blowers on high fan speed and the interior cooled down, this is what I was seeing for pressures at idle.

You must be registered for see images attach

 

[L31MaxExpress]

This is Four Seasons benifit listing on the 88947. GM HT6 must be 170cc rather than the 190cc I said in my previous post. My 97 has never cooled as well as it does now. It did cool very well with the Valeo replacement compressor that was on it for more than a decade. I am not sure on the displacement of that unit.

• Premium Quality 10 Cylinder compressor is more efficient and quieter than a 6 cylinder with 210 CC verses 170 CC. Premium compressors are built with Dowel Pins to prevent case twisting and leaks.

 

[Sjohns4]

I pulled a vacuum for 35 minutes. It’s a Sanden SD7H15. I had to use warm water to get the second can in. Will try increasing RPM and watching gauges this evening.

 

[1998_K1500_Sub]

I pulled a vacuum for 35 minutes.

Was there any flush used / remaining in the system before pulling vacuum?

What was the final reading? Did you change the vacuum pump oil?

Did it hold vacuum? When I have time, I'll let it sit overnight and check it in the morning.

 

[Sjohns4]

Was there any flush used / remaining in the system before pulling vacuum?

What was the final reading? Did you change the vacuum pump oil?

Did it hold vacuum? When I have time, I'll let it sit overnight and check it in the morning.

No flush used. Can’t remember final vac reading but low side gauge which shows vacuum was pegged. It held vacuum but only let it set a few minutes…was hoping to be riding in a cool cab today.
It’s been quite awhile since I changed the vac pump oil…I’ve probably pulled over a dozen systems down with it, both 134 and 410.

 

[L31MaxExpress]

One other tip I do have for a front orifice tube/rear expansion valve system. When the system is low the expansion valve will open all the way because of how it works and hog most of the refrigerant. The rear unit will be ice cold while the front unit is only slightly cool. Turn the rear blower off, forcing the expansion valves thermostatic bulb to close off the valve, limiting the flow. You can reduce blower speed to reduce low side pressure early in the charging process. When I start from a vacuum, I can usually get the first can almost completely into the system before I even start the engine. By the time I start the engine, the compressor no longer short cycles. When I get probably 75-80% of the capacity into the system, I then kick both blower motors on to high speed, bring the engine up to 1,500-2,000 rpm and add a few ounces at a time until I get the system charged where it needs to be. Many of the systems I charge do not have a capacity specification and I end up charging them by pressures and temperatures. I shoot for 6-9F superheat at the accumulator outlet with the blower fan(s) on high speed. Superheat temperature readings show me when the front evaportor core is properly saturated with refrigerant. I also try to make sure I have enough refrigerant to keep the evaporator around 35F at 2,000 rpm in ~100F ambients without having so much it drives the low side pressure higher and results in a warmer evaporation temperature.

Do you happen to remember the front orifice tube color? My 99 Tahoe and brothers 99 Suburban both had and called for Yellow orifice tubes up front and often people put a White/Black tube in by mistake. The correct front orifice should be equivalent to a Four Seasons 38887 and it should not have one in the condenser outlet.

In the past 10 years I have probably worked on a dozen dual evaporator SUVs as well. Probably 1/2 of them had been improperly serviced at some point and had an orifice tube in the condenser outlet. It has been such a problem with mechanics thinking they are knowing what they are doing, I actually open the connection and look on any system I am working on. I do not trust any prior work. My 99 Tahoe would not cool well when I first got it, it had an orifice tube installed in the condenser outlet and another one in-line as well as had a smaller truck condenser. It would not cool below 65-70F in 100F ambient. After correcting the problems it blew 35-40F from the center vent at 2,000 rpm.