Blower fan will not come on when car is cold, but after about 10 minutes of driving, everything works fine. Anyone else have this problem or know how to check the climate control without the special M/B test unit? Thanks.

I responded to this question in the tech help forum and I'm too lazy to rekey the response here.

Good luck,

Other than using the LED flashing diagnostics, a couple of things you can try.

The blower switch shares the same output/pin with the aux. pump. If the Aux. pump is drawing too much current, it can cause the fan to not run, permanently at some point. The aux pump is just behind the top of the cam cover, un-plug it and see if your symptom changes. If so, it is likely the aux pump which you can do without as its function is to circulate water through the heater core at idle/low rpm. Replace when convenient.

The blower can be accessed fairly easily if it is the problem. Remove the screen at the base of the windshield, remove the wiper assembly, remove four screws holding the black center panel of firewall behind the cam cover and move it toward the engine. Now un-clip the plastic shroud around the blower, the blower can be lubed in place at this point or remove the spring clip/strap holding the motor and the whole assembly should have enough clearance to lift out. R&R time for me was about 15minutes.

The blower's speed resistor pack is behind the battery, on the furthest-curbside end of the firewall. I believe that the plug is inserted from the passenger compartment side, but it can be serviced from beneath the hood.

Two more electrical components to the CC system are the vacuum solenoids, and the air-sample blower. These are both located beneath the passenger-side dashboard vent and can be accessed by removing the glovebox insert (with door in place), the vent can also be removed which allows you to push the duct down and out and opens up access to these components.

The fan speed switch is a very common problem. If this is the culprit then the blower will work normally (high) when the defrost button is pressed on the CCU, it bypasses the fan speed switch. I have bought three fan speed switches in the past week, the most expensive one so far was still under $20 and they all are perfect, check fleabay. The CCU on pre-'87 cars is different, if you are looking for a used one of these make sure the right-lower button is the recirc button, that's yours.

Our cars are relatively rare, only made the 190DT in '87 I believe, and only a 49-state car. Fortunately it shares many components with rows of used-up gassers in junkyards across the country, but take good care of the transmission, 2.65:1 rear screw, and rear CVs, they're not so common.

Good luck,

- Jeff Miller
190DT

I had a similar problem. The most likely case is that your pushbutton unit is on its way out.