308 fan switch over-ride switch

My switch is below the center A/C vents on my 308, right above the console. I ran the wires forward to a point above the forward end of the console and up through a rubber grommet that exits beneath the upper half of my spare tire shroud. I then routed around to the passenger side of the spare tire well and forward to the thermal switch and the fan motors ( for the indicator lights).
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Here are some handy specs taken out of my manual for a 1978 308 GTS US spec car.

Cooling system pressure maximum, 12.8 lbs/sq.in.

Maximum permitted tempurature, 230 degrees F to 240 degrees F, (Too high in my opinion!)

Thermal switch activation range is when tempurature exceeds 183F and the fans cut off when the temp drops below 167F

Thermostat begins to open when the tempurature reaches 176F to 185F AT THE THERMOSTAT (not the gage)

I agree with Hans that a 180 degree thermal switch MIGHT cycle the fans more often. The indicator lights should give me a good idea if that is true.

DJ

 

WHY do you want to run a wire thru the firewall???? Everything you need is in and around the relay board and fuse box.

The rad temp sw feeds a relay. You can simply jumper the connection there. The relay takes care of the rest.

 

You are absolutely correct. No need at all.
At the time I made the modification I had not had the relay panel out of the car and did not realize how much easier it would have been to make the modification there until I did the headlight bucket/ motor relay mod 8 months later. I felt at the time that the best place to tap the circuits was at the actual "point of use" to insure all of the circuits, relays, fuses and motors were performing from power input to power output. Granted, a rather crude way of doing it but effective.

Tapping into the system at the relay block will, of course, accomplish the same thing.

 

It did the same to me too. The relays are all marked as is the fuses. You may have to convert a couple of the terminals on INPUT side of the relay that reacts to the thermal switch with multiple spade adapters from radio shack. These you can hook your overide switch to. A diagram of the relay will be neccessary to tap into the correct terminals. The ones you want are the 'signal' terminals that receive voltage from the thermal switch.

If you want to use indicator lights as well you can tap into the OUTPUT side of the fan motor relays, there should be two. Installed in this fashion the lights will only indicate that the fan motors are receiving voltage through the fuses and relaysand DO NOT indicate that the fans are actually running.

I do not know how to set up the indicator lights to react directly to the operation of the fan motors themselves. Would it be diodes in ground cicuits of the motors, then to the lights? Any REAL electricians out there that can help us?

 

No, no, no. No need to fiddle with relay contacts, etc., or to even try to get behind the relay panel.

Find the color code of the appropriate wires from the diagram in the owners manual. You're looking for the wires from the radiator temp switch. Locate these wires in any convenient location under the dash. (OK, OK, that was a total oxymoron.) Now, use Scotchlock type connectors to tap into the wires. You don't have to cut anything, nor break the connection. The Scotchlock connectors simply pierce the insulation and allow you to electrically connect another wire to the circuit. All you are trying to do is to attach a simple SPST switch in parallel to (or across) the rad temp switch. It's simpler to do than it is to explain. You'll spend more time figuring out where you want to mount the switch.

As I don't have the info right in front of me, and my memory cells have swam in too much beer over the years, I can't remember if the rad switch has two wires, or if it simply grounds one wire. If there is only one wire, your task is slightly simpler. Just attach your switch to the one wire, and ground the other lead of the switch to any convenient point.

I don't have a wiring diagram right in front of me, but if there is any confusion over wire colors (ie - if there are duplicate colors), you might have to poke around with a meter to find the appropriate one.

I'll take a look at the wiring diagram when I get home and see if I can clear any of this up.

 

Hans,
The trouble with that approach on my GTS is the only place to access the wires are either at the relay/fuse block or up front under the bonnet. Otherwise the harness is relatively inaccessable. I am guessing it's a little easier on the GT4?

The relay block comes off with two screws (or so) and flips over upside down pretty easy. The fuse block has an extra set of spades behind each connector on the output side as well. Can't remember if the input side does as well.

My thermal switch has two wires connected to it and both seem to trail aft to the interior of the car.

 

By the way Doc, What kind of 308? GT4 or GTB/S?

 

My BB512i manual list maximum water temp as 110c-115c which is 230f-239f which I agree is tooo high. But, that is what Ferrari specifies.