superbm2day

Im pretty sure that this picture is of the cooling fan temperature switch. Its a 88 T/a 305 tbi. Can anyone tell me if that is the switch. I believe the the swtich has been bypassed by a previous owner. The fan runs continously after the car is started, regardless of the temp. The fan also appears to be jumped straight to the fuse panel. Does anybody know why this would be done. Thanks!

Forshock 85TA

that is a temp sender. Swith is under exhaust manifolds on passenger side.

superbm2day

thanks. I would have never found it. Is there any reference material out there for a 3rd gen, like the more specific detail, like wiring and locations of stuff likethe temp switch.

Trickster

Correction, that is the Coolant Temp Sensor (CTS) in that picture and not the Coolant Temp Sending unit. The coolant temp sending unit is located above the #1 sparkplug on the drivers side just beneath the exhaust manifold. It also only has one wire going to it.

superbm2day

so is that what controls, the fan? or is it located under th exhaust amnifold pass side?

Benm109

The switch that Forshock 85TA mentioned is the one that controls the fan. It's in the passenger side cylinder head, right below the exhaust manifold and right in between the #6 and #8 spark plugs.

Trickster

In addition to what Benm109 and Forshock 85TA have mentioned about the fan switch. It is located between the #6 & #8 sparkplugs above the starter. Please do not confuse it with the "Knock Sensor" located in the same general area but a little lower and in front of the starter.

superbm2day

ok what is the knock sensor while were on the topic? lol. You guys are just full of knowledge, i love it here!

Benm109

The knock sensor is on the middle of the passenger side of the engine block, right above where the oil pan bolts to the block. It has a single wire and connector on it that looks just like the connector for the fan switch (people confuse the 2 all the time).

The knock sensor just detects when the engine is knocking (as in pinging, preignition, spark knock, detonation, etc.). It usually happens from bad gas or using too low octane gas. It just lets the ECM knows this is happening, and the ECM will the usually retard the timing to try and eliminate it.

Looks like this:

homerunchamp

Ok dumb question here, but if the sensor in the passenger side head controls the fan, if it is bad will you get a code from the computer? Mine is not throwing any codes, but my fan will not kick on for anything. The gauge reads correctly so the one in the driver side head is good, and I already replaced the one in the intake manifold due to it being bad and the car giving me a code for that. But since doing that the engine light does not come on but fan still isnt working either. Thanks and sorry if I am rambling.

Forshock 85TA

Correct. the fan temp switch is just grounding the circuit. No connection to computer.

superbm2day

my fan was jerry rigged by the last owner, and it skips the switches, he wired it staight from the fan to the fuse panel. Im guessing cause some people think its better to have the fan running all the time. I dont see a problem with it other than the fact that it sticks out of the fuse panel like a fuse, causin some issues, and the fact that it runs after the car stops for like 30 seconds.

greggbruce

iTrader: (1)

there is a cooling fan relay that either the computer OR the fan switch on the passenger head will ground and turn on the fan(s). sorry yours is "hot wired", wiring diagrams will help you figure out how it's supposed to be-- but it's tough to figure out. the 86 I just bought is that way, and it has an auxillary fan installed too that has a switch under the steering wheel, yuk.
I wish that people that didn't know what they're doing wouldn't do it.
it'll probably take me a couple of hours to figure it out, and I have the wiring diagrams and stuff.

oh yeah, the computer doesn't see the fan switch, or the gague sender, it only sees the temp sender in the first picture in this thread.
so if the fans mess up, the computer won't notice it.
96 and newer computers will see it, however. (OBDII) (on board diagnostics 2)

homerunchamp

Cool, looks like I will try replacing the sender in the passenger head, thoug it looks like it will be a pain. Thanks for all the help, I am sure I will need more soon.