4430 Sanden Compressor

Changed over to sanden compressor and have blown a couple of relays. Didn't change the expansion valve but am in the process now, Probably initially overcharged the system but not according to gauges. Should my temp bulb be insulated to pipe? Any suggestions welcomed! No leaks but never would cool down. Also, I looked at evaporators and it appears some have heater hoses and some don't. Would like to bypass but think I should do it under the hood. Advice? Thanks!

I believe we talked about this before... if you are "blowing relays", that part your problem is caused by an electrical issue, NOT an "overcharged" or other issue on the refrigeration side.

The clutch coil should only draw maybe 7 to 10 Amps, if you are "blowing" relays likely rated in the 20 to 30 Amp range it should be OBVIOUS something is amiss electrically. I don't know where the relay gets it's power from in this aftermarket conversion, but I would THINK there'd be a fuse or breaker to blow or trip before the relay "blows".

BTW, what happens that indicates the relay has "blown"?

"Should my temp bulb be insulated to pipe?"

ASSUMING you are talking about the temperature sensing bulb that's a part of the expansion valve, it should be in clean, intimate contact with the evaporator outlet tube, but is covered over externally with cork/asphalt insulation to prevent condensation.

You need to figure out the electrical side first, why are the relays "blowing"?

Once you get this figured out and have the compressor clutch engaging reliably and the compressor operating reliably, post back with some hi and lo side pressures.

Unless you have unlimited funds (and time) you need to stop and think and listen to sage advice and troubleshoot this thing a bit instead of blindly forging ahead replacing parts without knowing why, IMHO.

You can either remove heater hoses from engine & install plugs in orifices or install manual cut-off valves. What pressures were on gauges when compressor clutch was engaged? How many ounces of refrigerant did you install?

Thanks for the reply Bob and Jim. I know we discussed this before, but I changed out relay last time for $10, and it has worked up until now. I added 3lbs of Freon per sanden info, but my pressures were still on the low side and ac not cold. I added a bit more. Last time I checked I believe my low pressure was around 35 on low and 250 on high side on a 90 degree day. Where do I get the cork/asphalt insulation?

Did you evacuate system for a good amount of time before installing refrigerant?

My advice is take it to some one who "Knows" what they are doing,,

Cork tape is usually carried by most HVAC techs, so if you know one of them you might get some. I have only seen it for sale in HVAC supply stores, but they are usually wholesale only. So I would check with a heating cooling shop. You will only need about a foot or so and they may sell you that instead of a full roll of 25 feet or so.

Vacuumed system for about an hour. About to pull FEL off so I can clean condenser. Already removed expansion valve and pulled evaporator out so I can clean it also. I thought I could read and get advice without having to take it to someone who knows. Always cost me a fortune when dealing with those kind. Thanks

I know what you mean,,,but you are all over the board with this, and wasting money as you go..it's like cutting the Puppy dogs tail off a little bit at a time so it won't hurt so bad....

Low side should be just above freezing so 28 PSI for 134a is just right. You got too much and of course it's not cold then. Still not cold at 28 PSI low side means restrictions in the system and/or undersized evaporator/condenser issues. With a possible bad expansion valve as the always applies issue. Using more freon just gets you a warmer evaporator which has two benefits and they both can count highly. First is time for a leaky system to still work without a refill and the other is a hedge against evaporator freezing. 35 PSI is about as high as I will go in that regard and since you are there and it never was satisfactory coolness in between we can assume your system has some serious defect that is not a lack of freon. Having a guy that knows his stuff take a look at it at this point is the wise call at this point, we really can't help without a good idea of the size of load you are working with along with everything else intangible across a keyboard.

Relays failing might be due to flyback inductance arc currents affecting the condition of the points on those relays. At the compressor wiring harness you should install a 30 amp diode to conduct the off current so the relay doesn't have to arc it across the points anymore. Anode of diode to ground wire supplying the compressor clutch and cathode (bar end of diode) to positive wire supplying power to compressor clutch will give your relays a good deal of longer life. As close to the compressor clutch as reasonably possible. 30 is way more than needed, but is also the over-engineering that keeps it working always. Voltage rating of diode of at least 100 PIV again just for overkill aspect. eBay has plenty. Don't tape up the diode, it needs to give off heat or it will die.

I don't think you need the insulation as I've seen many systems without any such considerations. Lucky to find one with a hose clamp for better contact.

Thanks for all the advice. I changed over to the sanden because the old ac delco went out. Did not change the expansion valve at change and feel like this is the only thing left. I took the evaporator out to clean while I am at it. When I put this back together I will add the correct amount of Freon and go through the sanden troubleshooting chart if I have issues. Thanks for the info. Will not be defeated!!!

You will need to change the expansion valve for the system to work properly. The expansion valve controls the amount of superheat in the evaporator and the bulb holds a refrigerant charge compatible with the system charge. There are other forces at work here such as spring and evaporator pressure that affect the expansion valve, but one with the wrong charge in the bulb will never function correctly.

The system will work without an insulated bulb but it will work better with one as it eliminates the effect of ambient temperature on the bulb causing it to react only to the refrigerant temperature.