Well, the little red wagon has a new trick: The air conditioner takes about 10 minutes to start cooling, and it's not very effective when it does.

I presume this is because the radiator fan doesn't start turning when the air conditioner's turned on, and only runs intermittently as the engine warms up.

The fan motor and fan relay work. Grounding either one of the two control pins turns on the fan.

Does anybody have a wiring diagram for this air conditioner? Can you help me identify the various pressure switches?

early 1993 with Regina, naturally aspirated

 

the compressor circuit is really simple. from the dashboard control unit, its a single green/red wire to the low pressure sensor on the side of the reciever/dryer, from that another green/red wire to the high pressure sensor on the condensor manifold, and a green/red/wire from that to the actual a/c compressor clutch. both sensors have to be closed, or the compressor doesn't run.

the electric radiator fan is two-speed, and is controlled by a relay behind the right headlight (on a non-turbo... on a turbo its on the other side). the low speed circuit is controlled by another low pressure sensor (not the same as the one above), and the high speed circuit is controlled by either a thermosensor in the radiator or another pressurestat. these presusrestats are both in the

the pressurestats are both in the condensor manifold.

 

Most likely you need more refrigerant in the system; it being low affects the pressure switch on the dryer which triggers the compressor and makes it cycle on and off...

 

The compressor runs just fine, 100% of the time. It's the radiator fan that cycles on & off.

Without tracing the wiring, how would I know which pressure switch is which? There are three in the condenser manifold.

 

thye are grey, brown, and violet. the violet one is the high pressure cutoff for the compressor. the brown (middle) one is the high speed fan pressure switch, and the grey one is the low speed fan pressure switch.

to check the fan itself, locate and unplug the fan relay, its a fairly big relay with 3 connectors. the red wire on pin 1A is power directly from the battery (on its own fusable link), verify this is live (volt meter from 1A to ground), if not find out why. the green wire on 1C is the fan low speed, jumpering 1A to 1C should spin the fan on low. the red wire on 2C is the fan high speed, jumpering 1A to 2C should spin the fan on high.

if the fan works, then I'd check the relay next. plug the relay back in. use a jumper wire to ground, and stick it into the back of connector 1B (blue-black wire) and the fan should spin at low speed. stick the ground wire into the back of connector 2B (white-black wire) and the fan should spin at high speed. if either of those doesn't work, odds are pretty good the fan relay is bad.


my 92, the fan comes on low as soon as the a/c is started. it only comes on high if the engine gets too hot normally, although I guess it also can come on if the a/c pressure gets too high.

what Lev said, other than those simple electrical fan tests above, you likely should have the AC refrigerant pressure and level checked by an A/C tech with the proper equipment. the system probably needs to be evacuated, leak tested, then recharged.

 

oops, I re-read your original post, you've already done the control circuit ground test, so yeah, skip to the A/C refrigerant leak down test and refill...

 

Thanks. That narrowed it down pretty quick. I pulled the connectors off and jumpered the pins. They each turned the fan on, one low speed, the other one high speed. But when you start the engine and turn on the air conditioner, the fan doesn't run until the engine warms up, and runs only some of the time when it does. (and yes, I remembered to plug them back in)

Now I only hope I can unscrew them without damaging the condenser ...

 

it is much more likely that you don't have adequate pressure in the AC, then that the sensors are bad.

 

That was the first thing I checked. And there's still the problem of the fan not running, so that's the current focus. I'll test the pressure switches next.
Sigh ... I do miss sight glasses.

 

Thanks. Do you know the pressures at which they're expected to actuate?

The low-pressure switch on the reciever/dryer clicks on at about 50 lb/in², which seems about right.
The low-speed fan pressure switch clicks on at about 260 lb/in², which seems awfully, awfully high.
The high-pressure cutoff switch and the high-speed fan pressure switch don't do anything at 290 lb/in², which is the highest pressure available to me.

I think I'm just going to replace all three condenser switches if they're not terribly expensive.
Same circuits as my '93? The fan shouldn't come on until either the radiator's warm or there's sufficient pressure in the condenser. Otherwise, you'd be running the fan unnecessarily, such as when you're cruising at high speed and there's adequate ram air, or when you're running the refrigeration loop at a low ambient temperature to provide defrosting or dehumidification. It's already a gas hog; there's no good reason to be running accessories that don't need to be running.

 

I wouldn't do anything until I recovered all of the refrigerant, installed a new receiver drier, new orifice tube and O-rings.

Then, charge the system using the correct amount of refrigerant as well as a couple of ounces of oil.

 

I'm pretty sure 93 is quite close to the 92. 92 940's had some big changes from 1991, a larger radiator, larger intercooler on turbos, no more mechanical fan on the water pump housing, larger 2 speed electric fan becoming the primary cooling fan.

 

I didn't see anywhere in the above posts what the gauge set reading were on the system. Provided they were in spec . I would consider hot wiring the fan to test if the overall system is functioning correctly. If it then cools correctly then start to chase down the fan issue.

 

All vehicles leak refrigerant over time. For a vehicle coming in that is 25 years old I would have to wonder if it really had either the correct refrigerant or enough. At some point, it might have been empty and filled without pulling a vacuum. For that reason, I would start over because the pressures do not seem right. You can't diagnose these systems without a proper refrigerant charge.

You can, however, take a guess all day long and end up spending hours and getting no where.

 

No, not all leak! I have a 1992 740 with R12 which has never leaked and is still working perfectly! A leak is a flaw somewhere in the system and can and should be addressed. It didn't leak when it was new, right? Many cars never leak.


Drcampbell, you are overthinking this as many Volvo people do, "do less!" should be the motto for Volvos! Just add some more refrigerant in the system and see what happens. I wouldn't worry about all the electric switches and fans at this point... Certainly wouldn't mess with the system replacing parts throwing money at some shop that probably knows no more than you about senior Volvos.

 

While you may have a system that has maintained a charge for a long time, those systems are not sealed as a home HVAC unit is with soldered connections. There are O-rings and seals which will hold pressure for many years, but after 10 years it is not uncommon to need some refrigerant. You could plot these statistically on a bell-shaped curve and there will always be outliers.

My suggestion came as a result of diagnosing these cars for 20 years. When I see high pressures with slow engagement I have to wonder if the system has air mixed in or some other condition. The only way to evaluate the system and to rule out all of the outliers is to start with a known good charge.

I was attacked for the suggestion.

 

Oh, sorry, I didn't mean to hurt your feelings but when I see a lot of wrong information I can't help but respond.



In this case as in many other older Volvos and DIY types, the idea is to save money, not go to a shop and come out with a $2,000 bill for A/C repair on a $1,000 car, don't you agree? I don't like to throw parts at a problem which only benefits the shops and often doesn't even resolve the issue. We are lucky that our cars are well made and easy to repair (that's why we love them) and forums such as this aim at keeping them affordable, that's the idea!

 

It was not you that did the attacking. That post has been deleted.

The refrigeration circuit on any vehicle is the base of the system. What the OP describes is not a quick fix, but go ahead and fire the parts cannon and randomly replace parts without a diagnosis. That, alone, wastes more money than getting a proper diagnosis.

Since I can do all of the AC work myself since I have the tools and certifications, I simply advised what I would do to properly diagnose the system.

I have seen lots of cases where someone worked on the AC who was not trained and ended up making a mess. I've seen high side pressures high enough to blow out O-rings because Mr/Ms mechanic didn't vacuum the air out of the system prior to pumping in the new refrigerant. The result - abnormal pressures and a system that will NEVER EVER perform properly.

The 93 Volvo system has a slight delay before the clutch engages but not 10 minutes.

 

Are you saying that you cannot add refrigerant to a system without first evacuating it to make sure there is no air in it? I am no expert on A/C but I have added refrigerant to cars and the A/C seemed to work OK, for a time at least.

 

Generally yes. But in this case, I would have started over. At this point I'm done with this thread. I came to help and got attacked. Let the OP fire the parts cannon and guess until time itself comes to an end. In the meantime, the OP can enjoy the warm weather.

I'm done.