Well, a year later and I an finally going to tackle the non-working AC in our 740 Wagon. I have looked around and found an entire kit on Rockauto for less than $300. It has a new compressor, drier, and orifice tube. It also converts it to R134a. My question, since I have no experience with AC work, is will I be able to install the parts and charge the system or should I just take it to someone and have them do it the right way? It has no freon and the compressor does not work, even when jumped, so I am guessing the system is empty.

I thought I could replace all the parts easy enough and then recharge myself, but I have been seeing that it has to be vacuumed out and pressurized, etc. What say you guys?

 

It's a pretty simple system and should be straight forward for most DIY'ers. Changing components shouldn't be a problem . The issue need to contend with is where the original system leaked. You'd have to sort that out during the vacuum down test. Also because the system has been empty for so long you'll need to get a flush kit and do the lines and condenser. You can rent a vacuum pump to evacuate the system . You should also get a set of gauges for the refill. Give it a go and let us know how it's going

 

and you might just find out the evaporator is bad, whereupon you get to tear your whole dashboard and center console out to get at it.

before replacing the compressor, do you know the current one is defective ?

 

Well, I did do the check where I unplug the relay from the drier and jumped the relay while the AC was turned on. The compressor did not come on. This was the only test I have read about to see if it is bad or not. To the best of my knowledge, the AC has not worked in about 4 years. It looks to be original to the car as well.

 

another useful test is to measure the voltage on the wire coming from the AC controller to said sensor. if you unplug that low pressure sensor, one of the two pins of the connector should have voltage on it relative to ground if the A/C is switched on.

if you do see voltage there, then its possible the high pressure cutoff switch has failed, this is the violet switch on the condenser manifold down off one side of the bottom of the radiator

 

Thank you for the information. I'll check that out this afternoon as well and report back.

 

I meant to also say that this idea of the evaporator being bad scares me a little. I replaced the heater core last winter and swore I would never get into this dash again. I am pretty good with a wrench, but that job absolutely SUCKED. I guess I have some thinking to do.

 

the good news is, I've not heard of too many bad evaporators on these volvos. its a known issue on similar generation mercedes.

 

By relay I assume you mean the low pressure switch. You need to jump the 2 wires together and not the low pressure switch. With a jumper wire in place the compressor will turn on regardless of having any freon in the system. You don't jump the switch you jump the wires. Just checking.

 

This is what another member told me... "You can "jumper" the compressor by shorting the pressure switch on the dryer near the schraeder valve--use a paper clip, plug is + and -. If the compressor runs at that point, chances are that the problem is lack of refrigerant due to a leak. " If that is the wrong procedure, I'll look at it again.

I am just not sure how deep I want to get into this. I can buy the entire kit for less than $300 as far as under hood components. But when Pierce brought up the evap, I really thought seriously about the work/reward return value. I have pulled a good bit of the interior to make HC repairs and swore I would never do that again. It may be bad, and it may not, but that is the gamble I have to decide whether or not it is worth it. If I do all of the work under the hood onlyto find out the evap leaks, I might get a stick of dynamite at that point LOL!

 

The simple thing would be to get a vacuum test of the system the way it sits today. If you have leaks then you can evaluate what needs to be done and about what it will cost. Go from there.