Guys,
I have no doubt that the incisive posts I've read hear about how easy it is to 'reflow' the solder connections on my wife's 94 nonturbo 940's air conditioning control unit -- but geez, getting it out sounds like a PAIN! (Great instructions on how to do it though - thanks!)Yet sometimes, according to posts I've read here, it STILL doesn't work once you've put it all back in. That would truly suck, dudes. So... I've replaced the long tube to the collector doohicky that was leaking (auto tranny cooling lines had rubbed a hole in it) and have re-pressurized the system -- but still had no AC clutch engagement until I applied direct power -- then the compressor blew ice cubes -- so I surmised that a) the control unit was bad, and b)the AC cooling system is just fine. So why not, I asked my shade tree friend, just run anAC bypass switch? There's at least two little panels on the dash that would perfectly fit a lighted rocker switch. I can run 16 gauge wire into the switch, which will be rated for 20 amps, along with an in-line fuse also rated for 20.
Will not, gentlemen, this work just fine? Only question is, where to I attach it on the AC system...

Guys, you are excellent posters. I welcome any sage comments. Thanks!
I'm enjoying this site a lot!

PDR

If you don't want to try resoldering the climate control circuit board, then your bypass will work as long as it feeds power into the low pressure switch on the a/c drier(vertical round cylinder just in front of passenger side firewall under the hood). If this switch is bypassed then the compressor will never cycle and the evaporator can freeze up.
--
John R.

Dear Foof,

Good p.m. Here's a procedure for this repair:

I. To access the climate control circuit board - the heart of the unit:

(a) Remove storage tray (removal bezel around lighter [lifts off with fingers, grip on the passenger side and pull gently], two Philips head screws, and three electrical connectors to the lighter)

(b) Remove the radio (see the FAQs, insert screwdrivers into slots on either side of the radio, about 1/4-3/8", at a 45 degree angle to the face of the radio, and push gently on each screw-driver [one at a time], while pulling on radio with fingers in the cassette opening)

(c) Remove the radio housing (two T-20 screws in the roof [if I recall correctly])

(d) Remove the steel radio housing support bracket (4 hex head machine screws, 10mm, two on either side)

(e) Remove the four philips-head screws in the front of the climate control unit and gently pull the unit forward, until you can access the back of the unit.

(f) The CCU should also have two electrical connectors (one for the fan selector switch, and the other for the control functions). Remove both.

(g) Remove the climate control vacuum lines block. This is a single piece of flexible plastic, to which all vacuum hoses are molded. The hoses likely will be of different colors. To remove this connector from the back of the ccu, simply pull it gently.

(h) Remove the climate control unit from the car

(i) Remove the climate control circuit board cover (shiny metal, four metal tabs, using a small flat-blade screw-driver and a needle-nose pliers [to straighten the tabs])

(j) Remove the climate control circuit board mounting screws (four)


II. To access the printed circuit board:

(a) Turn gently the four twisted metal tabs, which secure the shiny metal inspection plate.

(b) Once the tabs are straight, lift the plate gently, with a small, flat-blade screwdriver.

(c) Remove the four screws that secure the circuit board

(d) Do not touch the ribbon connector: the board can stay attached to the rest of the CCU, while you repair the printed circuit board.

(e) Find the relay, a square, box-like device towards the edge of the circuit board

(f) find the main electrical connector - opposite where the ribbon connector is attached - which electrical connector has 12 or 14 pins.

III. Reflow the solder to the relay (four pins) & to the main electrical connector (12 or 14 pins).

To reflow the solder

(a) use an electric soldering iron, with not more than 25 watts capacity (this limits risk of burn-out).

(b) Touch the tip of the iron to the pin for 1-2 seconds.

(c) Add a small amount of ROSIN core solder (this is NOT plumber's solder, which is acid core). Rosin Core solder is the ony solder to be used on electrical/electronic work. Acid core solder should NEVER be used on electrical/electronic items.

NOTE: The break causing the problem likely is too small to be seen with the naked eye. Thus, treat all of the solder joints noted above, as if any one could be the cause of the problem.

If this does not cure the problem - assuming there is no vacuum leak - you should have the system checked for under-the-hood problems.

Hope this makes the job go more smoothly.

Yours faithfully,

spook

Thank you, Spook. Your information is incisive, detailed, and easy to understand. You have a knack for techno prosody, and you seem to enjoy it, too. Ever think about technical writing?

Best,
Foof

Dear foof,

Good p.m. Removing the controller isn't that hard. If you look through my posts, I'm pretty sure I set forth a detailed procedure. The job should take about an hour.

When you reflow the solder, use a 25-watt soldering iron, rosin core solder only (not acid core, which will do damage, over time). It should take no more than 1-2 seconds of heating to reflow the solder, on each joint.

The relay (rectangular and black) is on the edge of the circuit board closest the to main connector. It has four contact points. Reflow the main connector joints (12 or 14 of them, I don't recall which), as they, too, carry a lot of current.

I think you'll find this will solve the problem, and not create other issues.

Feel free to ask any further questions.

Yours faithfully,

spook

I just bought a 945 with such a by-pass switch. Compressor kept freezing up. One of the first things I did was to solder that connection. The second was to remove the stupid toggle switch.

Gentleman,
I'm beginning to get the picture. When the word 'lazy' and the word 'stupid' appear in the first two posts one receives in answer to a query, it isn't hard to get the point.
Gentlemen, point taken.
I'll pull the fargin' board!
Grrr...this better work!
But hey...wait a minute...what if I ran an intermittent capacitor on the bypass switch...say a two minute on off cycling...
Just kidding.
Thanks for your tips,
PDR

OK, good and after you pull it some more advice. After you ID the relay pin that will be resolder you can take it to someone who is well versed in circut boards to reflow it because it is indeed delicate work. Second item advice is after repair you can set board back in and make temporary hook up to test it before you do all the parts/radio fini buckle down of the job. It will work if your pin connection is bad and the problem for lack of compressor engagement like the thousands of others that we have repaired.

"Park"

Park,
Thank you! I believe I may take your excellent advice. My last soldering was a Heathkit stereo in the mid 1980's as a kid -- and I did not do a very good job. The back of the board looked like pigeons had landed on it. It worked, but I think that was pure luck.

Thanks again for the good advice. If I can't do this now, I should hang up my DIY belt, and go get ripped at my 'local Volvo dealership' -- which is in Santa Monica, and which charges fargin' UNBELIEVABLE amounts for simple parts. California, my friends, has lost its collective mind...don't move out here! You'll regret it!

Good on you, Park, for the information.

Best,
Foof

I soldered my own but was not completely happy with the looks of the result, but it has worked fine for me so far. You do NOT want to take it to a Volvo dealership for this job!, they do not re-solder, they replace the whole board only, and I think it's like a 600$ part. That's why we do them ourself.

Good Luck Buddy
"Park"

Yes this has been done before, the problem is the compressor will run constantly and eventually freeze up your evaporator. The control board circut cycles the compressor on and off to mantain opti proper evap temp. Don't be so lazy, fix the board like the rest of us have.

"Park"