Frequently Asked Questions
The Mercedes W123 & W126 diesels are arguably the longest lasting and most durable vehicles ever made. Unfortunately, the majority were fitted with a weak, highly subpar air conditioning compressor - the Delco / Harrison R4. Klima Design Works offers W123 & W126 owners a way to install a vastly superior alternative, and move on from the constant and expensive headaches that accompany use of the OE unit. The OE Delco / Harrison R4 was designed by GM’s Delco Division in the 1970s, and was intended to be a low-cost, compact compressor that would save space in engine compartments that were projected to become increasingly smaller each year. Unlike GM’s standard-setting Delco A6 compressor – a stalwart of durability – service life was not a design priority with the R4. The “Scotch Yoke” internal configuration saves space, but brings compromises in durability and performance - especially with regard to noise, vibration, and harshness. Despite its flaws, it was produced in massive quantities and fitted to variety of vehicles. Later attempts to adapt it to R-134a were not particularly successful, though some improvements were made. These days, the R4 is an unfortunate relic of a less than admirable period in automotive design. When running R-134a refrigerant, an R4 can last as little as 1 year under severe service conditions. Under normal operating conditions, the practical life expectancy of an R4 often only 2 years. As many of our customers are aware, remanufactured R4s sold through discount auto parts stores are especially notorious. We’ve had many customers in hot climates report that prior to upgrading with our kit, they were forced to replace their R4 compressor every summer.
Service Life & Reliability: Sanden SD Series compressors are the most widely used and well know compressors in the world; they have a long track record of reliability, durability, and excellence. They are the #1 choice for custom and OEM vehicle builders in the trucking, heavy equipment, and aircraft industries. A Sanden SD compressor will outlast an R4 by many years.
Replacement & Replacement Cost: Sanden SD compressors are less expensive to replace than the R4, and easier to install and service. This equates to a parts and labor savings, not to mention reduced hassle. The universal ear mount design of the SD body has become an industry standard. Due to its widespread use, compressors compatible with this configuration are likely to be available long into the future.
Refrigerant Choice: The latest Sanden SD compressors are now chiefly R-134a compressors, whereas the R4 is chiefly an R-12 compressor. The R4 tolerates R-134a poorly, whereas the current Sanden SD models work well with R-12 & R-134a. Given the rising cost of R-12 and the hurdles to availability, the majority of users want a compressor that can use a refrigerant that is widely available.
Fuel Economy & Acceleration: Sanden SD compressors use less fuel and engine horsepower to operate than the R4. This means savings at the pump and better acceleration.
Smoother & Quieter: Sanden SD compressors are noticeably smoother and quieter than the R4.
Our kits are designed around a specific model number of the 7-cylinder Sanden SD7H15 series compressor. This is Model 4272, which we sell here in our webstore for your convenience. This compressor has a KG rear head and a 132mm diameter A2 double groove pulley and 12 volt clutch. If you wish, you can also use a Model 4709 with a 125mm pulley, though in this case you will have to source your own v-belt (we only include belts for the 132mm pulley in our kits). Please note that in the past, we recommended the 5-cylinder Sanden SD5H14 Model 6630, however we have updated our recommendations based on a clear performance and cost benefit favoring the SD7H15. The SD7H15 runs even smoother than the SD5H14 and has even greater durability. While you can still run a Model 6630, but there is no longer any cost advantage to doing so.
We recommend using double-end-capped PAG oil. Viscosity choice depends on your particular compressor. Double-end-capped PAG is compatible with R-12 & R-134a, and is chemically stable compared with single-end-capped PAG (R-134a only). Double-end-capped PAG is formulated such that is does not readily absorb moisture, and is less likely to form hydrofluoric acid if exposed to moisture. Of course, you can also use mineral oil, but only if you will be sticking with R-12.
Yes, it’s possible. Because our kits are set up for universal ear mount compressor bodies, the brackets will accommodate units such as a Seltec TM. However, unless you have a compelling reason to choose another brand and are willing to do custom work to address possible compatibility issues, just use a Sanden. Please note that we only offer tech support for kits that use a Sanden. Moreover, we do not recommend using low-cost Sanden clones (typically made in China), as these compressors generally do not last very long.
You need quite a few things in addition to a compressor mount, and the compressor mount will get you only halfway there. That’s why we created a complete mounting & conversion kit. Unlike a Sanden conversion in many other types of vehicles – such as a vintage American car or street rod - where putting in the compressor mount is pretty much the “entire job”, installing a Sanden on an OM616 or 617 diesel is a different story. The hoses and lines are complex, mounting space is tight, and there are considerations involving strain relief of the adjacent oil cooler lines. Plain and simple, you need a number of specialty parts to do the job, especially when it comes to the hose connections. We include the essentials that you need in our kits, making the job straightforward.
Not without custom adapters and hose components. That’s why our kits include the adapters, fittings, and hoses you need for a correct, elegant conversion, right out of the box. Because several of the fittings required are unavailable on the market, we contract manufacture the correct fittings through a US-based supplier. Save yourself time and money – get it from us and avoid an epic DIY adventure.
It’s not required, but we recommend that you do. Our compressor upgrade kit contains the key hoses needed for compressor conversion, but your system will still have three original equipment hoses remaining (depending on the vehicle), and those need to be good. The original hoses are not rated for R-134a, and though they may be saturated with enough mineral oil to hold R-134a, you’re taking a chance by keeping them. We have more and more customers experiencing challenges due to leaky old hoses. Mercedes dealers and many aftermarket parts suppliers stock at least some of these hoses. If you need help sourcing hoses, contact us and we’ll help you. Please note that a decent AC or hydraulic shop can rebuild the three remaining hoses for you, keeping the specialty fittings (required) but replacing the rubber portions.
Generally, most W123 & W126 Mercedes a/c systems use American SAE-sized refrigerant hose, fittings, and o-rings - regardless of whether or not they were sold in North America. However, the majority of the fasteners in the compressor mount assembly – nuts, bolts, washers, etc., are metric like the rest of the vehicle.
We are pleased to offer you technical support relating directly to the installation of our kits. Please contact us if you have an installation related question. Tech support is typically handled by email.
It largely depends on the knowledge and skill of the installer. As with any a/c compressor replacement job, flushing the system components can be time consuming - plain and simple - and has nothing to do with your specific choice of a/c compressor. Shops that specialize in a/c service know this, and have the knowlege, experience, and equipment to do it faster than a general service technician. When it comes to removal of the old compressor and mount, it will take roughly the same amout of time as when changing an R4. Bench prepping your new Sanden compressor and installing the mounting brackets and hose typcially takes between 2-4 hours. If you are a capable DIY mechanic but wish to have the compressor installed and system charged by a competant shop, you can save yourself money by removing the old compressor and mount yourself, as well as flushing the condenser, evaporator, and lines. These tasks are straightforward but consume the most amount of time. If you'd like some advice on how to save money on your installation, we're happy to help. Just send us an email or give us a call to learn more.
No, please expect normal performance. Changing your compressor is about enhancing reliability and longevity factors, and in itself won’t lead to colder air. Upgrading the condenser will get you to near R-12 performance with R-134a. Unless your system is malfunctioning, you should not expect to get air colder than about 35 degrees Fahrenheit. A properly functioning system keeps the evaporator just above the freezing mark, but the air moving through it will be slightly warmer by the time it comes out of the vents. Typical operating temps range from 35 degrees to 50 degrees Fahrenheit, though in extreme heat (e.g. 110 Fahrenheit), it is normal for temps to be higher. To get the most from your system (assuming your main hardware components are in order) it is important to verify that all of the vacuum baffles in the climate control system are operating properly, and that your blower motor reaches full speed when set to the max cool setting. Especially in the W123 models, insufficient air circulation due to failed vacuum baffle servos is a common problem. If you live in a hot climate, consider tinting your glass to reduce the load on your a/c system.
No. Our kits interface perfectly with the adjacent OEM components, and require no cutting, drilling, or welding or any other sort of modification of the OEM system. Even down to the electrical connector, our kits are 100% OEM compatible. While there would be no logical reason to do so, you could easily convert your vehicle back to an R4 setup if you so desired.
Yes. We’ll help you replace the failed bracket. We are routinely contacted by people looking to replace a broken compressor bracket that they bought from an individual on a forum. These amateur brackets – welded up in a home garage - were touted as being a cheaper alternative to our product. Unsurprisingly, they fail quite quickly - due to poor design, bad workmanship, and use of cheap, low-grade fasteners. If you’ve got a broken bracket, we’ll sell you a basic kit with just the components you need so you can move on.
We recommend using R-12 or R-134a in our systems. There are a variety of hydrocarbon refrigerants on the market that are considerably more efficient than R-12 or R-134a, though their safety and reliability is not certain. Be sure to comply with any applicable laws in your jurisdiction when choosing refrigerants.
If you are using an OM616 or OM617 engine in a boat, Land Rover, Jeep or other recreational vehicle and wish to install a compressor upgrade kit, please contact us for a recommendation. One of our existing kits may suit your needs, or you may require a custom kit.
Yes and no. Some of our products fit additional models that we don’t explicitly list. If you contact us, we’re happy to help you to determine compatibility. We have experience creating kits for Mercedes Geländewagen (GL) military and civilian vehicles fitted with OM617 engines.
We can help you to cross reference original part numbers and source replacement parts such as TXVs and blower motors for these systems. Most Clardy aftermarket systems for the W123 used either Sanden or Borg Warner ear mount compressors. Eventually, the aluminum compressor brackets fail beyond repair due to severe corrosion or fatigue. We’ve helped many folks bring their Clardy systems back to life - our compressor brackets are fully compatible with these systems. For Diavia, we can provide support as well. Please contact us if you need assistance.
Our current compressor upgrade kits are not compatible with vehicles that were fitted with York compressors, though there are a variety of York-to-Sanden kits on the market to help you with that.
We do not offer discounts of any kind, except in some cases on shipping. Our kits are made in USA in very small batches, and many of our parts are custom-machined. We import high-quality hardware –mostly from Germany - some of which is quite difficult to source. All of this costs money, and given the small scale of our production, we cannot afford to offer discounts.
Yes we do! We enjoy helping our international customers. We routinely ship to Australia, Canada, England, EU, Japan, Southeast Asia, and South America. We have also shipped to small island countries, Africa, Russia, and the Middle East. Our biggest international markets are Australia, the EU, and South America. Please contact us for a shipping quote.