Darkshot

iTrader: (4)

I cannot find any information on this site that explains proper operation of the single cooling fan. It does not come on. I have the car idleing in my driveway with a laptop hooked up. I watch the temperature go up, and up. The "Fan" light on the WhatsUp display on the laptop comes on, and the relay clicks, but the fan does not come on. I let the car idle up to 238, and the fan never came on. The dash guage was well into the red. The relay works, because if I ground the green/white wire that goes to the fan switch, the fan comes on.

Is the ECM supposed to be able to turn the fan on by itself? Or does it only rely on the fan switch in the head? Fan does come on with the AC.

abyliks

as stupid as this may sound, try putting the AC on, cause for some reason thats how mine is hooked up, for some reason

eagle_eyes

iTrader: (3)

i'm curious about this as well. my '91 bird gets hot when ideling because the fan never turns on. the relay is good, the wiring is good, the fan motor is good, but it doesn't turn on at temperature. the a/c doesn't work and the belt bypasses the compressor...but it should turn on at temperature anyways.

VenomX-87

there should be a switch in the inlet manifold that turnes it on and off at correct temp.
I had a faulty wire on mine and it didn't work but once it was replaced it would turn the fan on around 200 to 220 on the temp guage.
but i have a carb 305 and u got TBI 350 so i don't know if they are the same.

Up Dated:
Yeah i just looked it should have a fitting comming off where the T/stat housing is, check that could just be a lose wire or you could have a stuffed fan switch. all it dose is earth the fan so to test it just pull the wire off it and ground the wire, if the fan comes on it is the switch.

Darkshot

iTrader: (4)

I'm pretty sure the carbs and TBIs are set up differently. You have a TStat housing with two sensor holes in it...with TBI those are not used. There is a two wire sensor in the intake manifold, this is for reporting to the ECM the temp of the coolant. Then there is a single wire sensor in the head between cylinders #6 and #8, this is supposed to activate the fan at a certain temperature. There is also a switch in the AC system that turns the fan on with the AC.

I know that much, I'm just unclear how the logic operates. If my car was new right off the line, when should the fan come on and when should the fan turn off?

RBob

iTrader: (1)

A stock '91 TBI setup uses the switch in the passenger cylinder head. There is no ECM control of the fan. The switch activates at some high value, around 225-238 deg F. Can't recall the exact temperature.

To control it via the EBL setup, a wire needs to be run from the ECM to the fan relay (or the grn/wht wire at the switch).

RBob.

MrDude_1

RBob just said it....


the fan operates like this.

relay turnon +12v is provided by the ignition.
the relay ground can come from TWO sources. -- the thermal switch screwed into the passenger side of the engine block -- the AC system compressor ground (aka when the AC kicks on)


the power for the relay itself comes from the fuseible link connected on the starter silinoid, goes over to the drivers side for the relay... then comes back from the relay back along the way it came, up to the fan.




from your description of your problem, i would just goto a autoparts store and get the correct thermal switch... its the one for the passenger side block. one wire.

it is NOT the one in the thermostat housing.. that is only for the ECM.
it is NOT the one in the drivers side head.. that is only for the dashboard temp Gauge

VenomX-87

Ah ok i was just looking at blank TBI manifolds on the net and it had a hole very close to where my intake has the switch so i assumed that it was the same, my mistake.

RBob

iTrader: (1)

I was looking through a '92 FSM and discovered some interesting items. For a VIN E which is the L03 the fan switch is as such:

close at 238 F for fan on
open at 214 F for fan off

The A/C high pressure switch:

closed at 232 psi (and above) for fan on

And the kicker:

dash heat-A/C control in the Max & Norm position turns on the fan

These are all wired-or to the fan relay. Which means that any one will turn on the fan.

RBob.

Darkshot

iTrader: (4)

I am interested in simply abandoning the passenger side head switch and letting the EBL control the fan using the CTS reading, is this possible? I suppose I would just leave the switch in the head as a plug and re route the GRN/WHT wire through the firewall and to the EBL. Do you have instructions for this? I plan on keeping the stock single fan. I may change the motor though because I keep frying relays.

RBob

iTrader: (1)

Need to connect the grn/wht wire (was to switch in head) to pin C2 of the ECM. That pin (C2) may already be run under the hood. It is originally for the air port soleniod. If so can pick up the wire there and splice them together.

Then set the parameters under the FAN - section of the BIN.

RBob.