anyone remeber where it was?

I saw an article a while back on wiring a switch to your relay (tapping in) to allow the fan to come on manualy YET keep the oem temp switch working so when the switch is off, it still works. I cant find the article anymore though... Does anyone have a link they can help out with?

Thanks

-Red

The easiest way is just to wire up a new switch and relay, running the relay hot to the positive fan wire. This will allow you to turn on the fan at any time but will not effect the XJ's automatic system. IOW the automatic fan switch will turn on regardless of what position the manual switch is in.

so just run a switch to the power, dont worry about the ground?(since its grounded w/ the relay already?)


sorry not an electrician, a fabricator

-Red

It is a simple mod. The temp switch that starts the fan is mounted on the thermostat housing. There are two different variations. One is a normally open switch and the other is a normally closed switch. The easiest way to tell which one you have is to start the engine and then pull the connector off of the sensor. If the fan does not start, your task is to simply tap into both sides of the cable going to the switch and run them to a switch on your dash. When you close the switch on your dash the fan will start.

If the fan starts when you pull the connector, you will still run the same two wires to the dash, but instead of hooking them to the two sides of the switch, cut one wire to the sensor and patch the switch in series with that wire.

By doing it this way, the current pulled through your switch is very small and any switch can be used along with small wire. Personally, I use zip lamp cord, like you use on a lamp at home. You can buy it by the foot at your local hardware store.

Be careful here guys. I think the "switch" in the thermostat housing is actually a thermistor. A thermistor changes it's internal resistance with the amount of heat applied to it. This thermistor feeds it's information to the PCM. Then the PCM decides when to energize the fan relay. Don't mess with this thermistor or you will likely make the PCM very confused.

I have seen a write-up posted elsewhere to wire this "switch" to a relay coil. This will result in unpredictable temperatures for the relay to energize. It will energize with just enough current to pull it in and not latch the contacts well. This will result in premature relay failures.

Red did not say what year his XJ was and it is not listed on his public profile. If he has a 87 to 90, the solution is simple, just splice a switch in parallel with the 2 wires connecting to the thermostic switch located in the driver's side tank of the radiator. If it is post 90, go with another relay in parallel to the one the PCM controls. That way they both have the ability to switch the fan on and you won't screw with the PCM.

All the rigs I have seen have a switch at that point, not a temp sensor. There are two other temp sensor locations. One is at the rear of the head on the drivers side and is usually used to run the gauge. The second is on the driver's side of the block, just above the engine mount and below the manifolds.

I found the link I was talking about. Thanks guys....
It was simple, I just tapped into the relay on the side of the fender and WHOHOO I was up and running


thanks

Patrick

Redcbr007 said:

I found the link I was talking about.

Click to expand...

Wanna share with the rest of us?

Yucca-Man said:

Wanna share with the rest of us?

Click to expand...

Yeah, I want to do this mod too.

of course...do I look like the greedy type??? sheesh..

http://www.olypen.com/craigh/

-Red

What year is ur jeep?