I currently have a duel a/c system(ft & back a/c , independently controlled) on my all black 55 Dodge CRL hardtop. I'm due to have the system recharged for the summer car show season. It has been recommended to up grade my 5 valve Sanden compressor to a 7 valve Sanden compressor, to supposedly improve the cooling overall! Is that a wise thing to do(aproxx $450) or just recharge and wait another 2yrs to recharge again.
Posted 2018-05-29 10:55 AM (#564163 - in reply to #564136) Subject: Re: 5 valve vs 7 valve sanden compressor
Location: Simi Valley, CA
Well, I kinda of have to agree with you. My 2008 Nissan has never needed a recharge. I assume its due to the many connections and lenghts of hose that connects the two evaporators. I guess I'll take out the back seat so the shop can check all connections & hoses better. Also I was told the 7 valve comp was the type used in limos and would do a better job of keeping a all black car with a lot of window area cool.
Posted 2018-05-29 2:43 PM (#564179 - in reply to #564140) Subject: Re: 5 valve vs 7 valve sanden compressor
In automotive systems, some refrigerant leakage over time is perfectly normal; the question becomes "how much" and "how often" the system needs recharging is "normal".
The 7 series Sanden will pump more volume and, therefore, would seem more appropriate for a dual system but a simple check of the discharge temperature of both systems would indicate if more volume is necessary. IOW, if the discharge temperature at the registers is appropriate for the outside temperature then more volume might be a waste of money.
Posted 2018-05-29 2:50 PM (#564180 - in reply to #564163) Subject: Re: 5 valve vs 7 valve sanden compressor
Location: Hilltown, PA
If you are losing refrigerant, you have a leak. The real question is how much are you losing? For a dual evaporator system with line runs to the rear of the car I would expect a pretty substantial charge - I'm guessing but I would think 5+ lbs at the minimum. If you find the system to be 1/2lb low after 2 seasons I wouldn't give it much thought, but I suspect if you feel the cooling performance is poor that you're seeing leakage rates of at least 1/4 to 1/2 of the fully charged system capacity. Something that large you should find.
I also wonder if your system was assembled using proper hard lines and o-ringed fittings, or if it was done with long runs of hose and hose-clamped fittings. Newer refrigerants will find smaller holes, and pass through many hose types. Be sure whoever put your system together used components compatible with the refrigerant you used (such as lined hoses), avoided long hose runs, and absolutely no hose clamps - all connections to hoses should be crimped, and all threaded connections properly o-ringed.
As far as the compressor, a 7 valve (I suspect it's actually 7 piston or cylinder) will have greater maximum capacity that the smaller 5 valve, but will only make a big improvement if you are over-running the current compressor, and have the condenser capacity to take advantage of the upgrade.
Posted 2018-05-29 2:54 PM (#564182 - in reply to #564163) Subject: Re: 5 valve vs 7 valve sanden compressor
Burnemup - 2018-05-29 7:55 AM
Well, I kinda of have to agree with you. My 2008 Nissan has never needed a recharge.
How do you know it never needed a recharge? In most cases, a drop in efficiency triggers a recharge but the system will usually cool adequately with as much as 50% of the charge leaked off; "cool adequately" is determined by the individual comfort level.
The only way to know if the system has the correct charge is to evacuate the system and compare the weight of the evacuated charge to the correct fill spec and this requires a dedicated machine. (which happen to have)
Posted 2018-05-29 4:38 PM (#564190 - in reply to #564136) Subject: Re: 5 valve vs 7 valve sanden compressor
Location: Perth Australia
I recommend to my customers that their a/c systems get serviced yearly (inspection and replace gas), not many do because a/c is never a high priority until it doesn't work and its really hot.
The genuine system connections would be flare (I think) and I would bet the hoses are also factory, so R12 hoses.
I would recommend changing the hoses to R134a (barrier) hose purely on the suspected age of the hoses
Compressor shaft seal leaks on a sanden (any compressor actually) are not unheard of and a compressor change may repair the gas loss (if it is losing gas and its not just due diligence of your repairer recommending a service interval)
As for hoses and fittings, I have migrated to aero-crimp style on most of my a/c work now, mainly because the reduced size and flexibility makes it a lot better to work with on classic cars when fitting a/c into something that never had it. I do still use the standard thick wall hose on trucks and if the customer wants a more standard look to a repair or installation
Posted 2018-05-30 9:49 AM (#564237 - in reply to #564136) Subject: Re: 5 valve vs 7 valve sanden compressor
Location: Simi Valley, CA
OK! Thank you all for the info. I have had a suggestion that I remove the rear evaporator and only have the front under dash unit which would reduce the amount of R134 I need and after all ,most of the time I only have two people in the car anyway. I'm also considering a minor window tinting too! Or just do like I first said is to take out the back seat so all of the connections can be checked. I just hate to remove the rear system after I went through all the expense and fab to hook it up.