Which relay is for the cooling fan???

[Spankdamonkey]

Hi there everybody! I'm finally getting around to doing my cooling fan override switch (on the 'retta)....but when I went to tap into the fan relay (last step too!) the description in the how-to I read didn't match the wire colors on any of the relays. On any one of the four, there is no black/green wire

Anyone know which relay I'm looking for? I remember faintly someone mentioned it should be the second from the left? That one has a light blue, green, and red (x2) wires in it.

[bszopi]

When I did my override, I just cut the wie leading to the PCM from the relay. I then attached on side to the common leg of a switch. I then connected the switch legs of the switch to the other side of the wire and to ground, since that is all the PCM does anyway (ground the circuit to energize the fan). So, when the switch was in the OFF position, the PCM controlled the fan. When it was in the ON position, the circuit was grounded and the fan turned on. Here is the schematic (for my 94 Beretta) showing how the PCM and cooling fan relay interface:

[Spankdamonkey]

Thanks Brad!

Since I'm electrically challenged, I would want that dark green wire then? At least the other colors in your schematic match those on one of my relays

[bszopi]

Yes, it would be the dark green one. And I'll try to do text art for the switch...

PCM
|
\---\
GND PCM

If that makes any sense...

[Spankdamonkey]

Hmm......I hooked it up. It will turn the fan on, but it does it in a really weird way that I don't understand and can't rightly use.....

The fan will not spin up when I turn on the toggle switch. I found that it will only turn on when the wire is TOUCHED to the battery and released. (momentary contact to ground the relay?) It will run indefinitely after the touch-and-release until I switch off the toggle. If I hold the wire on the battery terminal after the fan starts up, it will kill the power to it......but ONLY as long as I hold it there. If I take that same wire and touch it to ground after the fan starts, it shuts it off. Strange.

So then, how do I make this work if the same wire that supplies power to the relay via the + battery terminal won't allow it to run when it is connected???

Sorry I can't explain it any better

[bszopi]

You are messing with the wire going to the PCM, correct? Are you messing with it at the relay? I did it under the dash, that is the reason I asked. I knew exactly which wire I needed to cut, so never got confused with how the relay was connected.

If you look at the diagram I have above, you will see how the relay functions, and possibly a way to determine if you are messing with the correct wire. First, lets see if you are using the right wire...

If you look at the diagram, there are numbers shown on the relay. These numbers should be on the actual relay as well. So make sure you are messing with the wire connected to the 86 terminal.

Now, if you look at the diagram, there is power going to the relay, split between the #30 and #85 terminal. If you have a voltmeter, you can verify which wires this is. One wire (#87 terminal) goes to the fan, and the other (#86 terminal) goes to the PCM. In order for the coil inside the relay to energize, you must complete the circuit. That is what the PCM does when it grounds the #86 terminal. This allows the internal switch to latch, thus sending power to the fan.

By reading your explanation, it just doesn't sound like you are switching the right wire, OR your relay is messed up. The circuit must be completed, or the coil will not stay energized, thus unlatching the internal switch.

[Spankdamonkey]

Brad,

I'm following the how-to off of Bstuff. I'm utilizing an extra relay, and this is how I have it set up: toggle switch to 85 contact (other end of toggle to chassis ground) , + battery terminal (fused) to 86 contact, Spliced additonal wire in on the previously mentioned + battery terminal wire (post fuse) to 87 contact, and spliced into the dark green wire from stock fan relay to the 30 contact.

Hopefully that explains it a bit better........

Should I be using a 3 contact switch or just 2?

I feel so stupid....

[bszopi]

Its getting late, and I need to go to bed. But I'll try to figure out what you are trying to do in the morning. I just went the easy route and didn't add another relay. I know the only downside to my method is you must remember to turn off the switch, as the fan will continue to run when the car is off. Not sure if your method is the same or not. I will draw it all out in the morning.

I used a 3 pole I guess... SPDT (single pole, dual throw). The middle pole went to the fan relay, and the 2 outer poles went to ground and the PCM.

[Superdave]

http://www.v6z24.com/howto/fan maybe that'll help.. the relay might be in a different spot though...