1998 S90 climate control relay location?

jefflamonica · Post by **jefflamonica** » 16 Feb 2016, 09:06

Hello. I'm new to this forum, as I've just recently bought a 1998 S90. So far, love the car, but need to fix a MCC climate control issue. The previous owner had removed the blower resistor because the fan was running even when the car was off and the key was out. I spoke with his mechanic about the issue to confirm. The P.O. ordered a new blower resistor, which I have, but he never returned to the shop to have it installed. The mechanic, and some on other forums, have speculated that a relay may be stuck closed and energizing the system. I'd like to find that climate control/blower relay and replace it.

I'm having trouble finding the relay diagrams for the S90 and locating that particular relay. One forum thread here for an 850 suggests there are two relays near the blower (high fan speed and low fan speed), but I won't know until I get in there this weekend. Can anyone guide me here? I'd like to be able to order the relay ahead of time, but suspect I won't know what to order until I pull the old one and get the part number off of it. As part of the overall repair process, I also plan to jumper the blower to make sure it's working, install the new blower resistor, replace the relay. And see what happens. Thanks!

lummert · Post by **lummert** » 16 Feb 2016, 19:10

Remove the glove box and look on top just above and to the left of the blower motor. It'll have 2 connectors. I have had a blower issue for the past several years with my 1988 760 (same system as your S90). I used a blower motor pigtail connector from a GM car (this climate system is built by Harrison France and uses a GM blower motor) and wired a 1.1 ohm ignition ballast resistor in the positive wire to the blower motor and ran a ground wire using a 20 amp switch to chassis ground (ground point is behind the ash tray on the transmission hump). Current to blower motor with 1.1 ohm ballast resistor is 7.5 volts, with .60 ohm ballast resistor 9 volts. The switch in the ground wire allows the blower motor to be switched on or off. I ran the positive wire to an ignition switched 12 volt source on the rear of the relay panel. As soon as it gets warm enough I'm going to use a 30 amp standard relay to switch the blower motor on and off.

May be a good idea to use an inline 30 amp fuse in the positive wire from the 12 volt source.

jefflamonica · Post by **jefflamonica** » 17 Feb 2016, 08:53

@lummert -

That's quite a hack. I was hoping to just locate and replace the associated relay(s), install the new blower resistor and go from there.

lummert · Post by **lummert** » 17 Feb 2016, 09:10

Here's what the critter looks like:

http://www.epartsland.com/products/volv ... ed-control

lummert · Post by **lummert** » 17 Feb 2016, 09:17

jefflamonica wrote:@lummert -

That's quite a hack. I was hoping to just locate and replace the associated relay(s), install the new blower resistor and go from there.

This hack required no cutting of the original wiring harness.

jefflamonica · Post by **jefflamonica** » 17 Feb 2016, 09:27

lummert wrote:Here's what the critter looks like:

http://www.epartsland.com/products/volv ... ed-control

I have a new one of these to install. This is the blower resistor. Would it also perform a "relay-like" function and possibly get stuck in the circuit-closed condition? Could I be searching for a relay that doesn't exist, and all I have to do is install the new resistor?