I have a colman mach about 1968 model

2 possible problem 1: bad heat sequencer . check for low voltage should have white wire and blue at low voltage And read 24 volts to turn the switch on. check voltage should have 220 on one sidenif relay all of the time when the switch is on and working should draw about 20 amps per 5kw eletric heat. if you have a brown wire instead of white then u should pair the white w1 with brown w2 which will call both strips at the same time. alsonrun your fan on low speed red wire. if its not any listed unplug high voltage and check strip for continuity may just be burnt

high speed relay or bad fan motor.

It could be the fan switch is not working on low speed or the motor windings are bad on lower speed

I am at a bit of a disadvantage here as I have never seen a 316 and my books and parts lists don't cover it, but here goes.
I expect that your car has only an electric fan, right? And you have already checked the fuses, right?
That fan should turn on low speed when the A/C compressor is running, or on low speed when the radiator gets to a certain temperature, or on high speed then the radiator gets really hot.
There should be a temperature sensor somewhere in one of the end-tanks on the radiator. If it has three wires, the switch is inside the sensor. The switch plug will have a ground wire and two wires that go to relays. The switch will ground one of the relay wires depending on the temperature. Grounding that wire activates a relay which turns on the fan.
With the key ON, If you unplug the sensor and ground each of the two relay wires to the ground wire in the plug (ground is usually brown on a BMW), you may be able to turn on the fan. If both speeds work, the problem is your temperature sensor. If only the high speed works, the problem is either the relay or the resistor in the fan. Most often, it is the relay. I don't know which relay it is on a 316, but the relay may click when you trigger it at the temperature sensor plug, even though it has failed. If it clicks, you can find it by the sound it makes.

no high speed ? fan motor relay, no slower speeds resister pack.or faulty fan switch.
Check motor with jumper lead from battery,but unplug power lead to motor first. check grounding wire to motor. if motor dont run replace!

Try a new fan motor. It runs about $125.00, It will run a few min. then will trip the motor themal switch. you can probably still here the compressor running. It may also trip the breaker on shore power . good luck! the part you are looking for is a 1/3 hp 115vac 2 speed 1580/1020 rpm part number #1468-3069

It's the mode switch contactors for the high setting just overview the wiring of the high cool or high fan contactors if it's not there check all leads for the high fan or high cool circuitry.

It sounds like you'll probably need a capacitor .......

jason, if you are willing to to a little wire tracing, you can do this! We're going to create a new switch function. Chances are that two of the wires are probably for the fan motor (high and low). I'm not sure about max and normal. This uses a two position switch. Figure out which wires go where...then...get a '3 way' switch from the hardware store (they contain a common and two 'poles') along with a plastic box to contain them, a double switch cover and some 'heavy duty zip cord'. This is lamp cord but a heavier grade called number 16 or number 14 (14 preferred). Extend each of the wires and tape the connections. Now, threading the wires into the power box, hook the two fan wires that come to the switch to the new switch. Now, the common terminals and the power supply wire (probably the black) should be hooked together. It should all work...ugly but functional. If you need an on/off switch, you can make that a three gang box and include a standard on/off switch. If you can figure out the max/normal function, you can either switch it on or off or either/or...depending on the switch function. Hope this helps.