Radiator fan relay wiring questions

[Sherman Kaplan]

In the continuing refurbishment of my 73 TCS I spent the afternoon working on installing a re-cored radiator and fitting a relay and override switch.  The radiator has a new spal fan and I had the radiator shop install a screw fitting so I could use a screw in fan switch.  I never liked the push in otter switch.   The new fan switch I have comes on at 82 centigrade and goes off at 67 centigrade. Does this sound correct?

 I would like to thank Joji Tokumoto and Tim Engle for their excellent articles on fitting a relay and override switch.  As the engine is not in the car (hence no battery) I cannot check to see if what I did works.   Here is a brief description.  Does this sound right?  Please also see my 2 questions at the end.

New solid brown wire (with separate fuse) from piggyback connector placed on fuse block to # 30 terminal on relay

New yellow/green wire from #85 terminal on relay to existing yellow/green wire from original fan motor wiring

Red wire from new spal fan to #87 terminal on relay

Black wire from new spal fan to common ground

New brown/green wire from #86 terminal to 3 way connector.  One brown/green wire from 3 way connector to fan switch on radiator. Black/green wire from wiring harness to fan switch on radiator.  Piggyback connector on radiator fan switch to connect brown/green and black/green wires.   Other black wire connector on radiator fan switch connected to common ground.

Second new brown/green wire from 3 way connector to switch under dash. Second connection on switch under dash connected to ground (dash to chassis bolt).

Added extra ground wire from dash chassis bolt to common ground near radiator (where radiator switch and fan motor are grounded).

What about the unused black/green wire from the wiring harness that was connected to the original fan?  Should I leave it alone and tape it off or should it be connected to ground?

There is also a separate smaller gauge solid black wire that was connected to one of the nuts on the original radiator fan motor.  There is a similar solid black wire connected to the outside nut on the heater fan motor.   What are these extra ground wires for?  They don’t show up on the wiring diagram.  Should I extend the solid black wire that was connected to the original radiator fan motor to the common ground? 

Another question, is there any way to connect a battery to check my work?  Besides checking the relay and switch I have replaced the dash so I’m curious to see if I connected everything correctly.  It will be quite a while until the engine is back in the car.

Thanks,
Sherman

[jbcollier]

Is the Spal fan a push fan or a pull fan?  Look at the curve in the fan’s blades.  The curve works like a “scoop” on the air.  If the fan is run backwards, it moves a lot less air.  Changing the direction of rotation is a matter of switching the wires — this may result in you powering the black wire and grounding the red wire and that’s fine.  Some fans also allow you to flip the fan on the motor to properly convert from pusher to puller or the reverse.

The screw-in rad fan switch is a great improvement.  Two questions arise:

What thermostat are you going to use?

Is the rad fan switch located in the rad inlet (hot), or rad outlet (cold)?

The rad fan switch you have chosen is fine for the outlet side (cold) with a 160F/71C thermostat.  If it is in the inlet side (hot) and/or with a hotter thermostat, then the rad fan may just switch on and stay on.

Myself, I try to keep the wiring used consistent with the original.  So a brown wire is un-fused, un-switched battery power.  The power wire you have run should be purple (fused, un-switched battery power).  Sounds picky but it make future generarations, and your future self, less likely to curse your present wire choices.

Finally, could you draw up a diagram of the changed wiring description?  It would save a lot of mental effort trying to visualize your long description.

[surfguitar58]

Following this thread with great interest. Is the aftermarket relay/override switch seen as a necessity for a TCS? Could you post a link to Joji and Tim's article? So far the temp gauge hovers at a reasonable level, but I have not yet driven the car on a really hot day.
Tom

[Grumblebuns]

Sherman,

I went read through what you did and have some questions on the Bolded text with my questions in red.

New solid brown wire (with separate fuse) from piggyback connector placed on fuse block to # 30 terminal on relay

New yellow/green wire from #85 terminal on relay to existing yellow/green wire from original fan motor wiring

did you replace the original YG wiring from the fuse block to the relay with new YG wiring? Unless the original YG wire was damaged, it should have been OK to re-use on the 85 terminal. 

Red wire from new spal fan to #87 terminal on relay

Black wire from new spal fan to common ground

New brown/green wire from #86 terminal to 3 way connector. One brown/green wire from 3 way connector to fan switch on radiator. Black/green wire from wiring harness to fan switch on radiator. Piggyback connector on radiator fan switch to connect brown/green and black/green wires. Other black wire connector on radiator fan switch connected to common ground.

I don't understand why you have the original Black/Green wire on the harness still connected to the fan (otter) switch. With the addition of the fan relay, the Black/Green wire from the fan should go directly to ground not to the fan switch but since you already have a new Black wire from the fan output to ground, the original B/G is redundant and can be tucked away.
There should only be two wires connected to the new fan switch, the Brown/Green wire (which you have) running from the 86 terminal via the three way connector and the Black ground wire from the fan switch to ground (which you also have).

Second new brown/green wire from 3 way connector to switch under dash. Second connection on switch under dash connected to ground (dash to chassis bolt).

Added extra ground wire from dash chassis bolt to common ground near radiator (where radiator switch and fan motor are grounded).

What about the unused black/green wire from the wiring harness that was connected to the original fan? Should I leave it alone and tape it off or should it be connected to ground?

I'm confused here. In the previous bolded text, I thought you connected the Black/Green wire to the fan switch



There is also a separate smaller gauge solid black wire that was connected to one of the nuts on the original radiator fan motor. There is a similar solid black wire connected to the outside nut on the heater fan motor. What are these extra ground wires for? They don’t show up on the wiring diagram. Should I extend the solid black wire that was connected to the original radiator fan motor to the common ground?
 
I don't believe solid copper core wire is used in automotive applications so maybe it's a PO modification.



Another question, is there any way to connect a battery to check my work? Besides checking the relay and switch I have replaced the dash so I’m curious to see if I connected everything correctly. It will be quite a while until the engine is back in the car.

Is your harness pretty complete and intact? If so, I don't see why you can't disconnect the stock Yellow wire coming from the ignition switch to the #3 fuse at the three way connector and use a jumper at the input to the #3 fuse and connect the jumper directly to a battery positive post. At the common ground point, run another jumper back to the negative post of the battery. Just remember that you need power both to the #3 fuse and the #30 terminal of the relay.

A schematic of you wiring set up would have been really helpful. It took me a while to sort of figure out you wiring layout.

Also the article on the fan override is in the Technical section and Tims Engles article is in the Documentation section of the KB under "Cooling"

[Sherman Kaplan]

Attached is a drawing of my wiring.  Sorry about the crudeness.  Please let me know if I can clarify anything.

Joji:

1.  I used the original yellow/green wiring from the harness.  I just extended some new yellow/green wire from the #85 terminal to the existing yellow/green wire for the original radiator fan motor.

2. I did not realize that the original black/green wire became redundant.  I will remove it from the fan switch and tape off.  I will also tape off the black/green wire where it exits the harness for the radiator fan motor.

3.  Sorry, not clear.  I was speaking about the black/green wire that was connected to the original radiator fan motor.  As mentioned above the black/green wire looks like it is no longer needed and I will tape off.

4.  By solid black I meant black with no tracer color.  My wiring harness is complete and original.  This is an extra stranded wire with a ring terminal.  It was connected to a nut on the original fan motor.  The heater motor has the same extra wire.  These wires do not show up on the wiring diagrams.  In searching the internet I found a reference to the Elan Plus 2.  Apparently, the extra wire on the radiator fan motor the shows up on the Elan Plus 2 wiring diagram.  No one on the Elan forum had an exact explanation as to why.  One person did say that it was for radio noise suppression for the electric motors.

5.  Thanks for the suggestion how to wire a battery to test the harness.

Tom:

Joji's article can be found here:

http://www.lotuseuropa.org/LotusForum/index.php?topic=1062.msg8705#msg8705

Joji has a link to Tim's article in the first paragraph.

I drove a 72 twin cam as a daily driver in California during the 70's.  I like an override switch as a "just in case" it's needed.

John:

The spal is a 10 inch pusher fan.  I haven't figured out the thermostat yet.  I moved to Colorado last year and we have real weather here, unlike Southern California.  It looks like  twin cam thermostats come in 3 temperature ratings, 74, 82 and 88 centigrade.  Would an 82 degree thermostat be a good compromise.

The new radiator fan switch is located in the same location as the original otter switch, closest to the bottom radiator hose. I believe this is the hot side.  I do have another switch that goes on at 82 and turns off at 77.  This may be a better choice.

I probably should switch the wiring to purple, but I probably won't     I  choose brown because originally I was going to follow Tim's wiring diagram and then changed my mind to follow Joji's.

Thanks to everyone.

Sherman

[Sherman Kaplan]

Sorry, it looks like my wiring diagram was attached as an attachment.  Here is another try:


Sherman

[jbcollier]

Better, thanks.

Wiring:

- I prefer to wire the rad fan so it can keep running after the key is turned off.  This helps with fuel evaporation on a hot day and can make for easier hot starts.  In order to achieve this, simply run a jumper from the 30 terminal to the 85 and disconnect the YG wire.

- Your brown feed to the relay’s 30 terminal, is it on the fused or unfused side of the fuse box?  It should be on the unfused side (brown) side to keep the number of connections to a minimum, and reduce load on the original fuses.

Rad fan switch and thermostat:

- Given the warm climate, go with a 74, or lower, thermostat.

- Both proposed rad fan switches are too low for the hot side of the rad.  I would recommend something in the range of a 90/86.  Both of your choices will result in the fan coming on and staying on.

[Sherman Kaplan]

Thanks,

1.  I will change the wiring so the fan can keep running.

2. I will double check to make sure the brown feed is on the unfused side.

3.  74 degree thermostat sounds good.

4. Looks like I need to source a new radiator fan switch. When you say 90/86 do you mean on at 90 and off at 86? I noticed that RD Enterprises has one that is on at 88 and off at 77. 

Sherman

[jbcollier]

88/77 is ok but it may stay on for a long time.  A Tridon TFS109 is rated at 90/85 and would be a good choice.

[Grumblebuns]

Sherman, if you remove the Black/Green wire from the fan switch and tuck it away, I believe the circuit should work as designed.

Better, thanks.

Wiring:

- I prefer to wire the rad fan so it can keep running after the key is turned off.  This helps with fuel evaporation on a hot day and can make for easier hot starts.  In order to achieve this, simply run a jumper from the 30 terminal to the 85 and disconnect the YG wire.

- Your brown feed to the relay’s 30 terminal, is it on the fused or unfused side of the fuse box?  It should be on the unfused side (brown) side to keep the number of connections to a minimum, and reduce load on the original fuses.

John, if the coolant is not circulating during the cool down period, does it make that much difference if you keep the radiator fan running with the engine shut down?

 

[jbcollier]

Sorry for the delay, I travelling in Portugal right now.

Given proper rad fan switch selection, the fan only runs when the thermostat is open.  Coolant will circulate very slowly due to thermo-siphoning — albeit an effect not very strong in a Europa given its convoluted cooling system.