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View Full Version : thermostat, relay, or sensor??? that's the question



Timpy311
07-14-2015, 05:43 AM
Well to start my first post I guess I should give some history as to how I came to this fork in the road. I used to have a 92 celica gt 2.2 5sfe m/t w/318xxx ended up having a few problems hit right when I found another fifth gen as a donor body. the donor was a 93 gt 5sfe a/t (for my girl) w/182xxx. After all is said and done the 92 donated both front strut's, the stealies, back rotors, pads, and calipers, breather tube and air filter, and some other random emissions parts and lil things. Also I put a brand new battery to solve any chance of tearing something up with a weak one or worse old (92 was roughly 5 years old according to the date code)

Okay now to my problem..... so I did the mass amounts of work that it needed and had her running like a decent car even after sitting for a year, until I developed a miss/skip/shutter. I lost power almost had to push it uphill. I was finally fed up and (since I had the plugs from the first car) I was changing them. while doing this I discovered one wire had arced through the plastic! I swapped them out from the other car also. problem solved runs like new the girl I bought it from says it ran better than when she had it lol.

So the final hurdle I'm trying to overcome is the fan. if I have everything correct the fan stops working and the car overheats. so I removed the fan fuse and ran a jumper to the battery for a constant run. I've unplugged the temp sensor to see if the fans kick on confirming a bad sensor yet nothing(everything is hooked up as should be). I do have a fail safe thermostat installed on the car. could the thermostat be bad and only thing that stops my overheating with the fan constant is the fail safe?? Yet it's not opening to cool when "factory". or is this the case of a bad relay? its got me stumped. as it is I drive fine and stay under half temp if I straight wire the fan. any ideas on how to correct this I hate having a constant fan, really its unnerving, I guess you could say OCD but I enjoy everything to function how it should rather than be rigged.

Any thoughts or ideas would be very helpful. I'm no novice and if given specifications I can test things with a multi meter.

Thanks for yours time
Tim

Nitro_Alltrac
07-14-2015, 04:50 PM
So with the sensor unplugged the fan doesn't come on?

Timpy311
07-14-2015, 08:44 PM
Correct, yet my gauge still functions properly. II also know there is two separate temp sensors. talked to a shop "mechanic" who said it sounds like the head gasket but I see no signs from it. oil is black, I know it needs changing but that will come after I solve the coolant issue, and the exhaust is dry also I don't have any power loss that I know of maybe a couple mpg cuz its age.

alltracman78
07-15-2015, 12:09 PM
For the fan; you probably have a bad fan relay [make sure you get the right one, there's 3]. Unless you have a bad fuse? You said you bypassed the fan fuse. Do you mean the fan relay?

Just for a little clarity, and hopefully so you learn something; the fan has no sensors. There is 1 switch on the bottom of the radiator. This is for the radiator fan only [fan inside the engine compartment, the on on the outside is the AC fan and only comes on when the AC is on]. If it is unplugged the radiator fan should come on. If it doesn't IIRC the No 1 fan relay is bad. This is off memory, I don't have the wiring book in front of me and I haven't dealt with this system in a looong time.

As far as the engine overheating, does it overheat when the fan runs? Or only if the fan isn't working? If it does it all the time, you have another problem. If it only does it when the fan won't work, it's probably just the broken fan system.

Timpy311
07-15-2015, 03:24 PM
Well first don't dumb it down I'm not retarded. and yes it only over heats when the fan is NOT working. I know there is only one relay and fuse and one sensor yes they consider that switch a sensor I've called the parts store. my jumper wire runs from the fan motor to the battery with the fan still plugged in, I know doing this will blow the fuse i have plenty extras frrom the junkyard. but from the sound no one reads or you would see that i covered almost everything and i have it singled out to just a few things. i thought tthis forum would help seems i found the illiterate bunch.

Timpy311
07-15-2015, 03:30 PM
Just so it doenst happen again. im having a problem with the radiator fan not working and i know which fan that is or it wouldnt have a jumper wire. the car does NOT over heat when i straight wire the fan.

Murgatroy
07-15-2015, 10:34 PM
Easy killer. Jeremy is trying to help you, he is easily the most knowledgeable person on the site. I won't go into his qualifications, but suffice it to say he is a certified expert. He isn't trying to dumb it down, he is trying to explain the situation the best he can in the limited situation provided. It is difficult to diagnose issues over the internet, and even harder to determine someone's skill level in two posts.

alltracman78
07-17-2015, 02:33 AM
You're fairly young [probably late teens or early 20s], you probably aren't a mechanic, and you need help with a simple circuit. So let's get something straight. You are a novice.
There's no shame in that.
So please don't get all worked up when someone who isn't a novice [I've been a mechanic for 16 years] tries to help you out. Your original post wasn't very clear, and even in your 3rd post when said no one reads and we're illiterate you STILL made mistakes.

First, I told you in my first sentence what's probably wrong.
Second, how is jumping a fuse going to make it blow? You're bypassing it. So it can't blow.....
I was trying to find out if the fuse was still good.
Third, there are 3 fan relays, not 1. The one that is probably bad is the No1 fan relay; not the No2 fan relay or the No3 fan relay.
Easy way to check.
-Unbypass the fuse.
-Remove the No1 fan relay.
-Jump the contact terminals in the fuse box[there's a diagram on the relay].
-Disconnect the fan switch [Toyota, who designed the circuit and the switch; calls it a switch, not a sensor]. If the fan runs, the relay is bad. If not, keep looking.

Shadowlife25
07-17-2015, 08:56 AM
You're fairly young [probably late teens or early 20s], you probably aren't a mechanic, and you need help with a simple circuit. So let's get something straight. You are a novice.
There's no shame in that.
So please don't get all worked up when someone who isn't a novice [I've been a mechanic for 16 years] tries to help you out. Your original post wasn't very clear, and even in your 3rd post when said no one reads and we're illiterate you STILL made mistakes.

First, I told you in my first sentence what's probably wrong.
Second, how is jumping a fuse going to make it blow? You're bypassing it. So it can't blow.....
I was trying to find out if the fuse was still good.
Third, there are 3 fan relays, not 1. The one that is probably bad is the No1 fan relay; not the No2 fan relay or the No3 fan relay.
Easy way to check.
-Unbypass the fuse.
-Remove the No1 fan relay.
-Jump the contact terminals in the fuse box[there's a diagram on the relay].
-Disconnect the fan switch [Toyota, who designed the circuit and the switch; calls it a switch, not a sensor]. If the fan runs, the relay is bad. If not, keep looking.

Quoted for posterity/