overheating problems 86 528e

I just purchased a 86 528e. I have problems with the car running hot when the AC is on. The auxillary electrical fan will come on when the temperature guage goes past 3/4, but should the electrical fan come on as soon as I turn on the AC?

the aux. fan has two speeds, 'normal' & 'high' and you may be hearing only the 'high' speed judged by the temp. you mentioned. The aux. fan should come on 'normal' speed as soon as the A/C is turn on [with the compressor]. If it doesn't come on, the 'normal speed resistor' mounted on the aux. fan has probably burnt out. The 'normal' speed switch on the radiator closes @ 196'F and the high speed switch closes @ 210'F. hope this helps.........jeffb.

You may also want to check the fan clutch and radiator. I'd do the fan clutch first since that is the cheapest of the two to replace.

While the engine is running, carefully stick a rolled up newspaper in the fan. If you can stop it, the fan clutch needs to be replaced.