XKE S2 Cooling Fans

Hi Friends!

As I continue on my quest to get my friends '71 XKE S2 back on the road… I keep running into issues… If I can get your suggestions, I would very much appreciate it!

  1. When I started the engine a couple of months ago, the new dueling cooling fans kicked in as they should, at the normal operating temp (6 o’clock degrees on the gauge).

  2. Did a few test drives around the block. On the third test drive, I noticed the engine temp rising. I made it home and while the temp was slightly below the “red”, it was pouring radiator fluid out of the over-flow tank.

  3. Engine cold - In testing, the fans kick on if directly hooked up to the battery

  4. Engine cold - With the key engaged, when I ground the otter switch I can hear the relay kicking

  5. Engine cold - With the key engaged, when I check the otter between the red/black and black connection points, it reads 12 volts? Should this not be zero when cold?

My friends, what else can I test? How can I fix? The fans worked perfectly before…

Thanks, Bob

  1. Past performance is not an indicator of future performance. Things break.
  2. I believe coolant should not have been pushed out if the gauge was not in the red. You may also have a gauge issue.
  3. Sounds like the fans themselves are good.
  4. Sounds like the otter switch and otter switch circuit is good, since you hear the relay. However, since you do not say so, I assume the fans did not turn on with the relay. Based on what you are telling us, It sounds as if the issue is in the circuit from the fuse to the contact tips in the relay, to the fans, including the wiring. You may wish to pull the wires off the relay, the two that go to the contact tips and jumper them to see if the fans run. I suspect the relay, but it could be one of the others,
  5. Your 12 volt reading at the otter switch is correct when the switch is cold and open. It would be 0 volts when hot and closed.
    Tom
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I agree it should not but suspect the problem is that you have air in the cooling system.

Air will cause a hot spot, abrupt boiling and enough pressure to force coolant out or even blow a heater hose off (what happened to me).

Did you drill a hole at 12:00 on the thermostat or do anything else to help assure no air was trapped as you filled with coolant?

I just rewired all this, so I’ll chip in. You need 12v at two places on your relay. One to close the relay points, the other to power the fans. The black with red stripe wire is just a circuit to ground the contact points in the relay. The green wire powers the fans, and provides power for the contacts. It seems like you have power at your relay, but the wire from relay to your fans is open, or your relay is toast.

Did you notice IF when the fans were inoperative was the tach inoperative as well?
That would indicate the fuse block might be an issue. #6 or #7 (can’t remember which). I actually carried a jumper wire in case that occurred until I replaced both my fuse blocks.

First, for the coolant pouring out of the header tank. Coolant expands as it heats. Eventually it will create enough pressure to open the cap. We can move on to your real problem, but not before noting that there should ALWAYS be air in the system when cold. If the tank is full, it will just cause the cap to open earlier.

When you short the otter, the relay clicks, but the fan doesn’t come on. That tells you that there’s power to the circuit and not much else. The fact that the relay clicks doesn’t mean it actually is capable of conducting power.

The Red/Black on the otter will see power through the relay coil any time the key is on. The black lead is ground, so you will get a positive measurement between the red/black and black leads. Disconnect the black wire from the otter, and measure voltage between the otter and the black wire. That should be zero, because the switch should be open.

image

My bet is that either the relay is bad, or you’ve screwed up the wiring. If this is an original Lucas relay, you can open the can and dress the points, which usually gets it working.

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Can someone please identify the “otter switch” and point out its physical location for the new owner of a '69 OTS?
A picture would be greatly appreciated.
Thank you
Ricardo

Ricardo,

Triangular switch bolted to the front of your radiator opposite the large top hose…

-David

Looks like David beat me to it, this one shows a Coolcat version of the ‘otter’ switch.
Cheers,
LLynn
IMG_7788 IMG_7789

Thank you both very much!
Ricardo

Michael,

I disconnected the black wire from the otter, turned on the key. Voltage measured 12+ volts.

This means the switch is closed? Now what, bad otter? Bad switch? I have a spare otter and have a new switch on the way…

Not sure how I screwed up the wiring, when it was working for a couple of months?

Thanks Michael & others for your suggestions and comments,
Bob

What are you measuring? Between the open terminal on the otter and ground? Between the black wire and ground?

I removed the black wire from the otter (ground). I then measured between the black and red/black wires, Bob

And when you touch those wires together???

Michael,

I removed the black wire from the otter and measured the voltage between the back wire and the red/black wire on the otter. The voltage measured 12+ volts.

I should be zero per your earlier post. What does this mean?

Thanks! Bob

No, between the two wires is 12v. If you separate the black wire from the otter, and measure between the black wire and the open terminal on the otter, it should be zero. As Karl says, what happens if you touch the two wires together?

Hi Michael,

Just did that, With the black wire removed from the otter and measure between the black wire and open otter terminal, I get a zero reading.

When I touch the black wire and the red/black wire together, nothing happens.

Thanks, Bob

Per Bob’s original post, item 4, he said when he grounded the otter switch he heard a relay click but no fans. That is why I suggested the relay tips may not be making, or a wiring issue. It could still be an otter switch that does not turn on at temperature, but first he needs to get the fans to run with the relay turning on.
Tom

Correct. Since the red/black has power, then touching the red/black wire to the black should cause the relay to close and the fan to turn on. Most likely explanation is a bad relay. Begin by removing the relay, open the can and dress the points and see if that helps.

Hi Guys,

Removed the relay and the case. The relay is bad! It appears to be a new one with electronics, no points. It was fried!

New relay on order. If the new one fries, then I have a load issue…

Thanks for all of your help!

Bob