Re: 164 Super cooling fan
I can get you part of the way to an answer based on my '94 Super 24V.
Don't know your level of expertise so apologies if I treat you as if you are inexperienced. To do this kind of work you really should have a multimeter and the manual (Cardisc).
This car has a dual speed fan as standard. There is a resistor on the fan cowling at about 1 o'clock (looked at from the front of the car) - this puts it right behind the relays. If you have a two speed fan, this resistor will be there.As to diagnosis, I can't help much on the air con bit (my air con doesn't work).
The lower speed comes on when a lower threshold temperature has been reached or when the air con is on. The higher speed comes on at high coolant temperature. The thermoswitch is fitted to the radiator right at the bottom below the alternator. Don't know if other switches for diferent temps. are available - shouldn't be needed if cooling system is otherwise OK.
First test the fan, resistor, grounds, relays and rad thermoswitch.
0. Starting point:
The fan will run so you already know the supply is good and at least one relay works. This also means that the chassis ground connection is good (wouldn't hurt to clean it) and the wire to it is OK.
1. Check clean relay contact pins:
Remove relay cover and carefully pull them out (both the same). Check that contacts are oxidation-free. There are sprays you can use to remove oxidation - I use gentle abrasion with green scotchbrite scourer and/or a fibreglass eraser. Smear pins and relay base socket holes with dielectric grease (silicon grease).
2. Test the fan/resistor:
Leave the relays out, ignition off or on (doesn't matter - I do it ign. off wherever poss.). Prepare a short length (say 150mm) of thick wire with both ends stripped. Find the relay base that has the thick light blue wire - this is for the low speed. Using the short length of wire, poke the stripped ends down the holes in the relay base that go to the blue wire and black wire (these are for the larger relay pins) - fan should run at low speed.
Do the same for the other relay base. This one has a thick brown wire that bypasses the resistor and runs the fan at high speed.
If only one speed works there's either a fault in the relay, wiring, resistor or thermoswitch. Prob low speed is suspect in your case - if so check resistor connections and clean them properly anyway.
Can't go to next step if both fan speds are not working here.
3. Test relays:
Can do this on or off the car.
Off car with multimeter (set to low resistance range, 200 ohms): coil resistance (between small tags) is about 80 ohms on mine. Resistance between big tags should of course be "infinite" with relay "off". Connect coil contacts across battery and listen for click. Holding contacts closed by leaving coil connected, measure resistance between big tags - should be almost zero. Helps to have another pair of hands doing this.
On car: plug relays into bases. Disconnect and unclip wiring from thermoswitch to relays (down next to thermoswitch, tied to radiator shroud). Thermoswitch has thick wires: white, brown (mine is red!) and black (ground). The connectors have thin wires goingto the relays: brown, brown/white and black. You want the connectors with the thin wires. Ignition on. Get your short piece of stripped wire. Put one end into the black wire's connector and the other end into the brown wire's connector next to it: should hear relay click and fan start on low speed. Now connect the black wire to the brown/white on the other loose connector: other relay clicks and the fan should go on high speed. If this doesn't happen for one of the speeds then swap relays over. If the fan speeds are not "swapped over", then it's a wiring/connection fault between thermoswitch connector and relay.
4. Test thermoswitch
Bit fiddly. On the car you should look for the resistance between the black wire and the white to go to almost zero at something like 90 celsius and the resistance between black and brown to go to virtually zero at something above (about 98C IIRC). You prob won't be able to measure the temp very easily. Off the car needs a beaker of water, decent thermometer and multimeter but then you haveto drain the rad andget the damn thing out...
Most likely fault is the resistor and connections IMO.
Usual disclaimer: if you **** something up it's your fault and if it all goes well it's mine!
HTH and good luck.
Last edited by mudhut; 15-07-07 at 15:15.
Reason: tech inaccuracy and minor clarification