Fan relay question

E-Type
1

I’m preparing to replace the otter switch because the PO bypassed it, but no relay was used. Instead, he ran a wire directly to the fans, so they’re on as soon as the car is started.

The mounted Lucas relay is still there and some wiring was connected, but it’s not in the circuit. I first tried to use the Lucas relay, but that brought no joy, so I used a Bosch relay I had. I wired it as per the CoolCats relay drawing (I grounded terminal 85 to bypass the otter switch). The fans worked after the relay was installed, and I considered the task successful, then by accident, the 85 terminal came loose from the relay, but the fans continued to run. With that said, I imagine connecting the 85 terminal to the otter switch would serve no purpose - or am I missing something? Any ideas?

Thank you
Carlo

2

If the 85 is disconnected, the relay is either shorted or not in circuit.

1 Like
3

You need to remove the Otter and test it in hot water - Meter set to ohms across the Otter connector and its body, warm the water slowly until meter shows zero resistance. Cooking thermometers can be useful here if you dont have a meter with a thermocouple attachment. I recently had a radiator faan switch die on me - supposed to close at 98C, didnt until ~103C.
jp

5

I was hoping you would respond, Mike.

Yes, you called it- the relay is bad, and as coincidence would have it, the ground was intermittent. With another relay and good ground, all is good.

For curiosity, the Lucas relay “clicked”, but didn’t activate the fans. What does that indicate?

Thanks for your input.
Carlo

6

To me, that would indicate dirty contacts in the relay or an open circuit thereafter

7

This is the opposite of the condition you described in the first post. Are we talking about the same relay?

85/86 are the winding connections. If the 85 is disconnected and the fans continue to operate, it means the contacts are bridged.

OTH, if the relay clicks, it means that both 85 and 86 are connected properly. If the fan ISN’T operating, it either means the contacts are carbon fouled or there’s a problem elsewhere in the circuit. Does this relay have both an 87 and an 87A? If so, maybe you’re using the wrong terminals.

8

Sorry for the confusion. The clicking sound is from when I tried the Lucas relay, not the Bosch relay. The first Bosch relay I installed continued to allow the fans to operate even though the wire was pulled from 85 terminal. Another Bosch relay is in now, and it is working as it should. On the new Bosch relay, 85 is still directly grounded and not grounded through the otter switch. This is until I get an otter switch.

Thank you
Carlo

9

I removed the relay from its housing and ran a burnishing tool across the contacts. The contacts appeared pitted, pitted enough that I thought their condition would prevent its proper operation. I got them clean and smooth, but the relay still didn’t work when put in circuit.

10

I just replaced My otter switch last year that was still working, as a preventative. If you’d like the old one, you are welcome to it.

11

Yours is a very kind gesture, Larry. PM sent.
Thank you
Carlo