t_g_farrell

iTrader: (1)

I know I mentioned in other posts about this but I thought
I'd write it up since I've gotten some IMs about how to do it.
I don't want to start a debate about using a thermo switch or
not for your electric fan mods. Thats a personal choice and
it also cost money

What I've done here is use some of the extra switches on the
transmission that normally signalled the igniter box for
some emissions stuff and repuposed them to turn my fans off when
I'm in 4th or 5th gear. It cost me zero to do and it also
gave me back 1 to 2 mpg on the highway. So its an easy free
mod that can also save you some bucks if you have an electric
fan with no thermo control.

Ok so heres the background. I installed these nice dual fans
from an MR2. They worked real good, all the time!



I was looking thru the FSM electrical diagrams for the SA when I
noticed a circuit that used two switches to tell the igniter
box when the transmission was in either overdrive or top gear
(4th). I tested the switches on the tranny per the manual and
they both worked. Heres the page from the FSM that describes them:



I then went and grabbed the FSM electrical diagrams and started
hunting for the connector in the transmission harness to see where I
could use these switches. Turns out theres a nice two prong
connector that comes up right under the MC with a GO (green orange stripe)
wire and a BrB (brown black stripe) wire right there. Its x-13 in
the diagram. See the red circles. Nice art huh!



Since I had depinned my harness I had some extra female two prong
connectors so I wired this into one leg of my fan cicuit. It basically
interrupts the ground side of the circuit for the fan relays and
stops the fans in 4th or 5th gear.

Some things to note when doing this are that the bullet connections
on the harness and the transmission may need to be cleaned and
the female connectors crimped a bit back together so they make good
contact. When I first started checking this circuit out it wouldn't
work because they had bad connections. Also check the transmission
harness to make sure it hasn't been abused and is shorting against
anything as that could play hell with the fan relays too.

Enjoy.

Tim

Jeezus

iTrader: (4)

Nice write-up! Wonder if it is just for SA's and not FB's?

I like how you kept small paragraphs. Some people post huge pictures and it ends up having to move the screen left and right all the time.

t_g_farrell

iTrader: (1)

Its all based on an SA, thats what I have. But I'm pretty sure it applies to all 1st gens. I'd have to look thru the elect diagrams to be sure. I'll check on it tomorrow.

blackdeath647

iTrader: (2)

very awesome, thanks for the post

t_g_farrell

iTrader: (1)

From looking at the wiring diagrams for 83 and 85 FB it looks like theres no way to do this. So I guess its SA specific. Sorry guys. If you happen to have a tranny from an SA in your FB you can easily hook this up using some bullet connectors.

t_g_farrell

iTrader: (1)

Now that I think about, the FB trannys may have these switches on them and they're just not used. Soemone would need to verify it. I don't have an FB tranny to look at here.

BlackWorksInc

I'm pretty sure FB Trannies have those switches and they're just not used, but its been a while since I inspected my FB tranny so I may be off.

trochoid

iTrader: (6)

Not sure if I'm too fond of this idea. I do a good deal of my driving in town in 3rd gear at 30-35 mph, I don't really need the fan turned on a that speed. While I applaud you ingenuity and resourcefulness, I still prefer using a thermostat to operate my electric fan.

t_g_farrell

iTrader: (1)

Like I said, not here to debate the merits of thermo control or not. Just a cheap way to turn the fan off in 4th and 5th gear. Its still on in 3rd, unless thats a typo on your part.

74RX4

iTrader: (10)

I think Trochoid is saying he would like it to go off at lower speeds and in any gear. Clever idea. GSLSE transmission has an over top switch (blue wires right side) that controls the ACV valve. I can't find description in the FSM, but the 84 Training manual says it is off only in 5th.

t_g_farrell

iTrader: (1)

I get his point, but for most cases if I'm in 3rd or lower the fans pretty much need to be on fairly often especially in hot weather. Besides I'm cheap and don't want to drop $20 bucks on the thermo control. I am a 1st gen owner after all

trochoid

iTrader: (6)

Not a typo, nor was I trying to get into a debate over thermo switches. The point about doing most of my driving in 3rd gear is that with your setup, the fan would be on all the time, even when it doesn't need to be on. That right there negates any gas savings achieved with it being off in 4th-5th gear. I'm THE #1 tightass when it comes to spending money on building a 7, but the cooling system is one area where we shoudn't cheap out. After all, in the long run, I'd rather spend 20-25 on a thermo switch instead of having to spring for a rebuild due to overheating.

Fwiw, when I installed an electric fan and thermo switch, it was less work than your mod, but I had also previously installed the 2nd gen underhood fuse block which made tapping power for the fan and relay easier.

t_g_farrell

iTrader: (1)

Theres no way my mod will contribute to overheating. In normal driving if your in 4th or 5th gear you will be going fast enough that the normal air flow through the radiator is more than enough to cool the engine. In any lower gears my fans on all the time so its over cooling if anything.

Also I do most of my 7 driving on the highway or on 45 mph or higher speed limit roads so I'm pretty much in 4th or 5th most of the time. If your in 3rd gear a lot you need to get out and clear that carbon out once in awhile

trochoid

iTrader: (6)

Oh I get the carbon cleaned out, trust me on that. Most of my trips are in town and often short enough that the engine often doesn't get warmed up. But then it's the FC that's my DD and fuel injection does have is pluses. I wouldn't treat the carbed 1st gen widebody the same way. It fouls out the plugs too easily if it's not warmed up before shut down.