Radiator Fan Motor Repair

When I got the car, the fan, along with other bits and pieces, was disconnected and in the boot! Obviously I did need to refit this fan (see Refitting the motor: ancillaries), but before I did so I tested it lying horizontally in the boot. It sprang immediately to life. However, now that its fitted, I can find no life in it at all! I had expected an electrical fault in the fan control circuitry as the motor had been rewired for constant operation; suggesting that the otter switch at least was faulty... but I hadn't expected a fault in the fan itself! Shorting the otter switch does result in power down the green and black wire to the fan so the activation relay is working, but there is no movement from the fan. Even running a direct live and earth to the terminals this time failed to induce movement. Looking at the SAE (aka WM12)  2 pin connector on the rear of the fan shows that it was damaged and loose... so it may be simply a bad contact internally. Alternatively the change in position to vertical could affect contact made if the motor brushes are very worn and bearings or mountings allow some "sag" in the spindle. Since the fan has spent an unknown amount of time wired for permanent operation it may be very worn internally.  It may be possible to repair the fan, although it is obsolete technology, and replacement with a Kenlowe or equivalent might be necessary. However, since I do want to preserve originality where possible, I will try a repair first. In either circumstances... whether repairing or replacing, the first step has to be to remove the fan once more.

My fan in position- looks great... doesn't work!

Its a bit hard to get at the cowling bolts so I undid the three M10 nuts and washers holding the fan motor to the cowl

... and the fan can then be fiddled out upwards.

 I did find this reference to the problem in a similar Lotus, the fan I think is identical, here on another forum. I followed this with a few mods as below.

Note- fan seems to be a Ford unit I think from the Fiesta!

I checked the fan shaft for play and found none so I'm assuming the bearings are OK.

Rear of fan- end plate nuts at 8 and 2 O clock

The end plate is held on by 2 nuts, but these are attached to long machine screws that penetrate through the motor and to undo them you have to hold the M7 below the fan and unscrew the M8 at the base plate.

M8 nuts (end plate) and M7 below fan

I'm sure this would be easier if I could get the fan off- I did try- it was held on with a rusty E clip over a washer.

Fan retention clip and washer

 Removing the E clip simply broke it! The washer came off but the fan wouldn't budge. As I don't know whether its screwed or pressed on (I suspect pressed) I didn't want to use a puller, so I simply left it and worked around the inconvenience. Its not too bad and if doing this again I'd just leave it.

Broke C or E clip and washer

Once the through bolts were loose the end plate lifts off. This was much easier than I had expected because all of the wiring is contained on the end plate and there are no trailing, fragile and pullable wires penetrating down inside the motor.

Removing end plate

The brushes are held onto the underside of the end plate on a fibreboard stage. They had plenty of meat left, and were free to slide up and down in their grooves.

Spring loaded brushes and wire connections

I covered the brushes with tape to hold them in place and protect them whilst I fiddled around with the end plate!

Inside the motor the commutator was clean- it seems to have been re-machined at some point because its recessed below the original diameter, but it seems to be in good condition.

Returning to the end plate- this is the contact damage I had noticed; the power terminal is loose and moveable.

Now I could access the brush contacts on the inside I was able to check whether the connector was to blame. It was- but to my surprise it wasn't the damaged pin that was out of contact but the earth contact (recessed) that was not connected to the brush.

No connection between recessed terminal and blue wire to brush!

This obviously needs fixing if possible. I can't find a source for fit-your-own SAE connectors, but they are readily available as pre-wired fly leads for Sealey or Schumacher bty chargers. I ordered a few of these because they seemed cheap and I'm sure will be useful. However, it was at this point (halfway through my fix), that I discovered that the nice new connectors were actually coming from China and would take about 3 weeks to get here! That's no good so I decided to make a repair using conventional bullet connectors and I will swap them for a weatherproof 2-pin connector later. I'm not happy about this because I like to keep as much original material as possible, but needs must! If you are doing this I recommend you get the new connectors before starting!

The end plate SAE connector seen side-on has a big circular pad underneath the end plate. Its obviously not going to pull out downwards and I can't lever it out upwards unless I remove the fibreboard stage by undoing the rivets and that's too much trouble. 

 Anyway, the circular pad should be useful, so in a departure from the earlier method, I decided to leave it in place and just cut off the external part  of the connector using a Dremmel.

Dremmel off external section of SAE connector.

Once this was cut off the two metal contacts that penetrate to the wires are visible. I was able to check that both of these made good contact with the brushes on the back. I have therefore removed whatever part was broken- so thats good news!

Metal contacts penetrating through the SAE connector- one left one right. Central spot is just a hole.

 I then excavated a bit more of this odd chewing-gum like material using a drill bit in the Dremmel

Metal terminals inside matrix

 This revealed the metal tags to which the wires were fixed so I could pull those forward, cut off the metal terminals and pull both wires back through to the inside of the end plate

Terminals removed and wires pulled through

 This leaves the white circular structure in place to act as a guide for the new wires on exit. You need to think about where the wires will join and then cut them to length before adding the extensions.

I soldered on about 4 inches of new wire

And slipped on (and heated)some heat-shrink tubing to cover the joins.

 The new wires were then fed back out through the circular pad

 and appropriate terminals crimped on.

I checked that the new wires were making good contact right through from new terminal to the relevant brush and then reassembled the motor.

The brushes can be fiddly to get in place but their grooves are designed to hold them back if they are angled like this. This gives enough space between them to allow them to slip over the commutator. Make sure the wires are routed out of the way so that the brushes will be free to move when released.

As they are positioned above (ie at 9 and 3 O clock) you can see that pushing the inner edge of each down from the top would free them from their retaining groove and allow them to slip forward along their grooves and onto the commutator. Study the position and direction of "push" needed because its hard to see once the end plate is on. Note line of brushes is 90 degrees to the line of the two mounting bolts holes.

Fit the end plate, if you just ease it out carefully you can see the brushes inside- there is one below just above the screw terminal for instance.

 I pushed the  inner edges of both brushes down (ie across the end plate and down into the picture as seen above) using a section of thin wooden lolly stick or craft stick. There is an audible click when each is released and slips inwards to contact the commutator.

You can then tighten the bolts again- here is the finished motor and you can see how the white pad remaining from the SAE terminal provides a semblance of a seal for the new wiring.

I replaced the washer and E clips on the fan- my new clips were much thinner than the old and so I used two to make sure I filled the groove on the shaft.

 I tested the fan using a direct feed from the battery to the new terminals and it worked straight away with no nasty noises. I was therefore able to finally  refit the fan and test in position. It still worked although there was a graunching sound caused by having moved the cowling struts during fan removal. These were easily bent back into position reinstalled.

Well So far so good as they say! However I think I am still stuck with the wiring problem and I will need to study that some more. At present the fan will only work if + and - battery terminals are connected directly to the two new leads. Shorting out the otter switch doesn't turn on the fan even though it does turn on a 12V supply down the green and black to red feed wire!

Fan wiring operation
Well, thank goodness this is an older car with a simpler fan circuit!

The fan draws its operating current directly from the bty positive post- but via  the fan relay (the lowest of 3 in the driver's footwell). Normally this feed is interrupted by the relay so the fan doesn't operate. The otter switch draws its power from the Aux terminal on the ignition switch, if the motor is cold then the switch is open circuit and power goes no farther. If the motor is hot the switch closes and then feeds power to the relay activation terminals. This  flows to earth across the relay, activating the solenoid action to close the battery feed to the fan. If the solenoid fails, then the power coming in from the otter switch cannot flow to earth and instead is forced down the fan fail circuit where it flows through and illuminates the fan fail light, passes through the fan fail diode and then flows to earth through the fan- I think this current has been greatly reduced by passing through the fan fail light so that there is not enough power here to run the fan. This means firstly that the fan fail light is really a relay fail light and doesn't actually tell you about the condition of the fan. Secondly, because power will only flow through this circuit when the otter switch is closed and the relay inactive, the lamp will not illuminate as a self-test function when the ignition is first turned on. Finally the fan fail diode is there to stop current flowing backwards round the fail circuit during normal operation. If the diode fails the fan warning light will either not work at all (broken connection in diode) or will illuminate all the time the fan is on despite the fan working normally (current gating failure). The diode is tested by removing the relay and shorting the otter switch- this should cause the fan fail to illuminate and in my case did so nicely. I eventually tracked my problem down to a missing fuse. Oddly although a single fan should operate through fuse 22, I found that  fuse 23 was needed for operation so I left both in position. I think the odd 12v feed to fan that I had observed previously is probably fan fail current running through the fan but too weak to start it.

Of course, I still do not know if the otter switch itself will function, but at least I do now know that there is no real fault with the fan or control circuitry itself!

On a side note, the other warning light in the car is the choke/low fuel light. This also does not illuminate for self-test when the ign is operated. I found it came to life straight away when the choke was pulled, However- I have an empty tank and so assume that the low fuel light should be illuminated even if the choke isn't operated- its not so I may have a sender problem as well.  I can't tell if the gauge is working because the tank is empty! I need to find out how the low fuel light works and see whether I can explain it. I have added this discussion to the entry "Fuel system tank to carbs".