Hi everyone-just joined-should have done it a long time ago.Have been a long time Volvo owner for some time,presently each of my kids have a 850.Have a question--After doing some PM on my daughters car,I disconnected the wire for her compressor because it was constantly cycling and it's very low on freon.I don't know if it's coincidental or not ,but since then I've replaced her alternator and battery.I know Volvos have some strange engineering sometimes.Now,she tells me her car was acting strange,dash lites for warnings were appearing,and the headlites first got dim,did'nt seem to be charging,then the engine would'nt turn over.We're 260 miles apart so if anyone has some good advice for me for next Mon.when I go and help her,it would be greatly appreciated.Sounds like a short somewhere-not looking forward to try and finding it.

 

Bad Alt. or bad connection on one of the wires.

 

Hello Mr. tuney443,

Greetings from freezing Chicagoland.

As you noted, Volvo's electrical/electronic systems can be very fickle sometimes. Anyway, I think people want to know more details about the case.

What kind of battery did you buy? Cheap batteries from franchise stores are not recommended, as they might have been on the shelf too long and the electrolyte may be low, exposing the top of the plates, which dramatically shortens battery life. A good battery costs at least $80-$100 range (I usually go with Interstate Batteries). Additionally, modern cars require that the battery be fully charged when you install a new alternator. Also, make sure that the connections are good & tight.

What kind of alternator did you install? I hope you bought a new/rebuilt Bosch (OEM) with lifetime warranty. I bought a rebuilt alternator from local Pepboys and it failed only after 3 weeks or so (the voltage regulator was shot). So I took it back and they gave me another one, and this one seems to be working fine.

Dash lights appear when the alternator is getting weak, they all start flashing until the car dies and wouldn't start again. My prejudice tells me that the alternator may be defective. Also, is the serpentine belt routing correct? The 850 uses 2 different lengths belts, short one for OEM and longer one for later improvement. The later belt has more contact with the alternator pulley (recommended). These belts require different routings. Double check the electrical connections for the alternator as well make sure they're not loose.

Some stores such as Autozone can test your alternator for free. I would also test the battery with the following methods:

1. Voltage Test with a digital multimeter (Sears Craftsman would suffice for most home mechanics). A good battery should read at least 12.3 volts.

2. Specific Gravity Test with a hydrometer. This is not necessary for maintenance-free batteries. This is a cheap tool yet proves useful. Do wear eye-protection if you decide to do this yourself, electrolyte sometimes spills out when you remove the caps.

3. Load Test. This should be done at a reputable shop, as this procedure requires diagnostic equipment.

850's absolutely require good alternator + battery combination, or it would not be happy at all.

PS: As for the A/C compressor, 850's have notorious compressor cycling. It usually turns the A/C off when you really need it. My 850 was not low on R134a, but the compressor kept cycling off. The thermostat on the compressor was a bad design and it has to be bypassed (jump-wired). Adding R134a is easy, though care should be taken.

Again, please give us more details as to the problems/symptoms so we can better help you.

Best regards,


JPN

 

what exactly happened with this thermostat and what does it sense? I allways thought automotive A/C cycled on pressure switches not temperature switches??
Mike

 

Hello Mr. MikeySq,

Greetings again from zzz...

Good question, I don't know what exactly happened, either way the compressor was a bad design, you'll see the comp is Made in Japan!

Anyway, it may very well be a pressure sensing switch, but when the compressor gets hot, it turns off. It may be thermostat too, or it may just be a pressure sensing switch. Either way certain wires have to be jumped, I haven't tried this since the A/C was still working though it wasn't at full capacity.

Nothing is more annoying than an A/C that doesn't work. However, A/C may not be a necessity in Sweden.

Night,


JPN

 

I'll takea look in to the wiring of the system and see what's in there that breaks the circuit for the compressor. Typically there's a low pressure switch which cycles the compressor for cooling capacity and there would be a high pressure switch as a safety to cut the compressor if refrigerant pressure gets to high.

Is your A/C condenser fan working? If it is not it is possible that the high side pressure of the system is shutting it off, and if that high shide switch is bypassed you could be running too high of a head pressure which could have dammaging effects on the compressor, .pulley or the belt because of the increased load on it, especially when car is not moving

maybe it could be worth a shot, usually safetys, however annoying they are are usually there for a good readon, maybe you should get a set of a./c gauges and stick them on there to see what it's doing.

Just a thought!
-Mike

 

I've been twirling wrenches for 37 years,so yeah I know the basics.What I'm asking here really is that disconnect at the compressor--is that wire somehow connected in any way to charging?The Gatorback belt I replaced last week when I did the alternator and battery R+R seemed the same lenghth as the existing--anyway, routed the same way--seems fine.Maybe it could be alternator's not charging--first thing I'll check--did'nt have meter with me. Thanks.

 

So forgot to ask--should I reconnect the wire to the compressor even though it's probably got no freon and will continue to cycle?Adding freon is not an option-I have to work on this outside in a college parking lot.

 

Hello again Mr. tuney443,

Good morning from Chicagoland.

I just looked at Haynes Manual's wiring diagram, and I do not see A/C-related components on the starting & charging diagram. Usually an A/C compressor should not have any effect in charging system performance (but there are always exceptions).

If the A/C is low on charge, I would leave the wire disconnected, but probably cover it with electrical tape to make sure it does not touch the chassis or other components. A/C compressor may be damaged if used, while the refrigerant (R134a) level is lower than it should be. Pulling fuse for the A/C is another option, but I am not sure if 850 had a fuse that only controls A/C compressor, many systems seem to share one fuse. Just re-connecting the wire on A/C compressor wouldn't hurt anything, unless the A/C is activated.

Adding R134a is easy these days, you can buy a kit for about $30-$40. It is a gauge + hose combo, sometimes come with a can of R134a, but you can buy a can of R134a separate and they are about $10 or less/can. A can of R134a probably has PAG oil in it too, which makes the job easier but you want to read the back of the bottle. I bought one & used one this past summer and it was easy, run the engine, turn the A/C on at max cooling setting and charge the system on low side (you can't miss it, 850 has obvious valve and label that indicate where to connect the charging hose, it's on passenger side, near the ECU box). It's worth a try but please do read the directions carefully & wear eye-protection, should you decide to do this yourself.

As Mr. Tech has noted, the alternator seems the culprit. I know it's pain to dig through to get to the alternator, but I would take it out and take it to a shop where they can test it. I took mine to a local Autozone and it was shot.

Good luck and please tell us of your progress.


Best regards,


JPN

 

No it will not have anything to do with the chaging system
You could unplug the compressor or the Low pressure switch.

The Battery cables are Known to mess up on the 850's.

See if you have output from the Alt. If so then check at the battery. If you have none there probe the wire before the terminal for power.