The AC compressor on my wife's '94 945t will not come on. I can disconnect the lead to the compressor clutch and jumper it to the battery positive terminal and the clutch engages, the compressor spins and very cold air blows into the cabin. I am not getting 12 volts from what I assume would be the climate control module.

It is of the type with three knobs: Fan, Airflow Direction, Temp, and has two buttons. One for recirculate, one for AC on / off.

With the dash lights on (parking or headlights on) the reciculate button lights when pushed. The AC button does not. I expect a broken switch or maybe a fuse somewhere but don't see any fuses in the box that are blown or associated with the AC compressor. There are two labelled for the blower and they're both good.

I did manage to pull the climate control module a few inches out of the dash but found it has a number of vacuum lines attached and as I didn't have the console sides or stereo removed access was limited. I found the levers behind the Recirculate and AC buttons which engage their respective switches, but can't confirm that the contacts aren't damaged or traces broken without pulling the console, etc.

Is there a fuse for the AC system somewhere other than in the fuse tray? Should I just replace the climate module with a salvage yard pull?

Please help. Temps will be in the high 80s this week and the wife is eyeing my 850 with it's cold AC.

Erwin

Got the unit out of the dash without having to remove the console, radio, etc. Two metal tabs that the two lower mounting screws run through can be bent back and the CCU slide right out. A little tight getting to the connections and vacuum line block but it's out.

This isn't the first time for this car. The unit is a Programainc replacement part, dated 3rd quarter of 2006. About six months before we bought the car.

It's apart on the bench and the suspect solder joint doesn't look cracked but not completely done as the pad on the board is half missing.

Here's the unit on their site.

http://programainc.com/categories.aspx?idcategory=4443&cl=1


ER

Fixed. Bad solder joint on relay.

Hello
in the 700/900 FAQ there is instructions how to resolder and fix this problem.
but i would jumper the a.c. switch first its on the dryer.
Mike

Jumpered the switch on the receiver/dryer and didn't make a difference. I did peruse the FAQ and found what I believe will do the trick. Resoldering the relay and other cold or fractured joints on the climate control module.

Going to pull it this weekend.

Erwin

If you resolder, then don't bother trying to reflow; remove the old and put on new solder. Extensive experience with this/these, have done 5.

Dear jerryc,

Hope you're well. What's to be gained by removing the factory-applied solder? If the solder is heated to the point where it liquefies - i.e., turns from dull gray to shiny silver - then any micro-cracks in the connections will be closed.

It is especially important to do this on the solder joints, where the main connector attaches to the circuit board. There are also four solder joints - where the main relay is attached to the circuit board - that also must be re-flowed.

Hope this helps.

Yours faithfully,

Spook

Spook, I'm no expert on the finer points of solder. All I know is that someone experienced reflowed 3 of these and they all failed. On one I then had installed a new relay, the little Digikey one mentioned in the FAQ. That worked, and then it was decided that the original relay was probably fine and possibly of better quality so that one was removed and resoldered on a different unit. Both those work.

May be getting into semantics here but I'll take the heat. ;^) When I said I'd "resolder" the connections, which I've done countless times in my career and with various old stuff projects, what I should have said was "sweat."

Sweating a solder joint is to heat to molten, then let cool. Re-flow describes it too.

To resolder could imply actually removing the existing solder with either a vacuum pump or Solder-Wik, then applying new solder. This I do when I find a cracked pad or trace that needs repair or jumpering.

It's all a judgement call based on experience, but the result is the same. A repaired electrical connection, whether on a board, in a relay or wherever.

The types that is almost impossible to repair are multi-layer boards with traces sandwiched inside the laminated circuit board. Pull out a feed through hole by not heating it sufficiently, or over-heating it, and you've got a challenge on your hands if you don't know where the trace surfaces or makes contact with another pad.

Thanks guys. Wife should have AC by Sunday.

Erwin

Just an addition to the reflow vs. resolder ideas, neither work if any impurities exist not allowing the solder to "wet". That is why many do the desolder witha wick or vacuum device-reflux-new solder.
FWIW What also must be added is that most pads, that is, the circuit board solder area, can be lifted off the circuit board by too much heat. A technique that gets the connecting lead hot enough to flow the solder and transitioning the heat to the pad in a wiping motion resulting in a cohesive flow on both is best. When doing an eyelet, the goal is still to keep the heat evenly distributed that the whole assembly heats at the same rate without overheating either part.

Dear vigilante,

Hope you're well. I concur: if there's a "dry" joint - where the solder never bonded properly - then there's no alternative, but to remove the failed solder, prep the surface carefully, and re-solder.

On these MCC units, the solder joints develop micro-cracks, as the solder heats and cools repeatedly, over many years. Re-flowing the solder, closes the micro-cracks, and current flows.

Your comments as to the correct method to apply solder - witout overheating the board - are most helpful and should go into the site's FAQs.

Yours faithfully,

Spook