RWD - A/C Compressor, no electric power to switches

Volvo RWD 900 Forum

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A/C Compressor, no electric power to switches 900 1995

Dear Mecmagus,

May this find you well. The "power unit" for airconditioning is located on a circuit board, which is in the Manual Climate Control (MCC) unit, the three-knob unit, which is mounted above the radio.

On the circuit board, there's a relay. It is connected to the board by four pins. These tend to develop micro-cracks in the solder joint. These micro-cracks may be too small to be seen with the unaided eye. To cure the problem you need to re-flow the solder on these joints, and on the 12 pins of the main connector on this circuit board.

To remove the MCC you must:
(a) Remove the front center console ashtray (lift the bar at the bottom and pull the ashtray forward, having first moved the transmission lever into 1st gear).
(b) Remove the storage tray (remove the bezel around the lighter, by pulling out and to your left, and then remove the two screws behind the bezel, after which you can rotate the storage tray's left side to your right, allowing you to disconnect the wires;
(c) Remove the radio (see the FAQs, for the procedure)
(d) Remove the T-20 screws in the roof of the plastic box, in which the radio is housed
(e) Remove the four hex head bolts, that secure the brackets supporting the MCC unit
(f) Remove the four philips head screws at the front of the MCC
(g) Disconnect the electrical and vacuum connectors behind the MCC
(h) Gently lift the bright metal tabs, on the cover behind the MCC switches
(i) Remove the screws that secure the circuit board to the base
(j) Gently turn over the circuit board. You will see the relay's pins (four; the relay is a black plastic box, about 3/4" long and 1/2" wide) and the main connector pins (12)
(k) Reflow the solder on the main connector and the relay. Take a 25-watt soldering iron and touch the tip to each joint, for 1-2 seconds. When the solder changes from dull gray to bright and shiny, you've closed any micro-cracks.
(l) Reverse this procedure to put things back.

Hope this helps.

Yours faithfully,




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New A/C Compressor, no electric power to switches [900][1995]
posted by  someone claiming to be Mecmagus  on Thu Jul 12 06:18 CST 2007 >

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