Hey guys, well now that winter is almost over and I have my garage back I can start Testing and Tuning my car. I still have a few minor problems to work out and was wondering if anyone had any idea's. My problem is this. My Engine Temp guage does not work. I have no clue how hot my engine is running. I've mucked with it to much that I don't even know what I've done. So I've decided to get a new radiator and fan(aftermarket). So I guess my first question is:

How do I wire that new fan into the fiero wiring(84). I know one wire is ground and the other goes into the fan switch under the left headlight but where in that switch?

Then from there how do I wire in a temperature sensor into my dash.

Then how do I make it all work so my fan comes on when its supposed to?

I've looked at all the fiero diagrams and still can not make heads or tails of it. If anyone has experience with the temperature sensor on a 4.9 and how you wired it I would appreciate your insight.

Thanks.

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I have no clue on how te Caddilac fans work. But I do know how an 84 works.

One plug has one wire coming out of it, all that does is ground the circuit when the coolant reaches a certain temperature. By grounding the wire it turns the fan relay on that is in front of the drivers side headlight. My switch does not work on my car (its new too?) so I added a manual switch, all I did was tap into the sensor wire under the dash, run it to a switch, and then to a ground.

Temperature guage, I am not sure of, but there has to be a simmilar plug, or something on the 4.9. The plugs may be different, but hopefully, if they work the same, you can just solder the wires together. I think the temp sensor is a variable resistor thing, the more voltage to the guage, the warmer the guage shows. So the hotter the sensor is, the more current it lets through.

I hope this is some help

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Details on my Fiero here
Member of the Edmonto Fiero Club Please rate me if I helped you!

I have done 2 swaps. A SBC and a 3800SC. Both times I simply used the stock temp sending unit from the Fiero motor and put it in the new one. No wireing changes needed. I would at least do that with the temp gauge. However, if you're going with an aftermarket Rad Fan, get the one with the thermostatic switch. It goes right into the Radiator and controls the fan.
Kevin

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85 Fiero-based ASPP GT-40 MarkII. 3800 S/C, Auto, Held suspension all around with 2" drop spindles and sport fr. end. RCC bump-steer correction. Mr. Mike's interior.

yes, lucky you, the ECM has nothing to do with the fan or the guage.
all you need is a stock fiero fan switch (or lower temp, if you like - at least 10* hotter than your thermostat), and a stock fiero temp sensing unit (for guage - not ECM)
you'll need to find places to put these sensors in - where they will hit coolant. good chance there are existing holes, but I couldnt say.
then you will need to run the wires to meet the original lines. I dont have my service manual here, or I could give you wire colors, and most likely locations to hit them

Ok, thx for your reply's. The Radiator fan with its own temperature sensor is a good idea and I will look into that.
The thing is that i've try'd all your suggestions. Its that my wiring was messed up before I even did this swap so I want to redo it completely.

quote If anyone has experience with the temperature sensor on a 4.9...

The 4.9 only has one NPT port in coolant. You can't put an ECM sensor, a guage sensor and a fan switch all in one port. Get a three terminal coolant sender for a '99 GTP. One wire is used for the guage. the other two go to the ECM. The ECM grounds the fan relay and the relay turns the fan on when needed.

quote Temperature guage, I am not sure of, but there has to be a simmilar plug, or something on the 4.9.

There is none. 4.9 Cadillac has no temp guage. There is a thermal switch on the rear cylinder head to trigger a warning light at some outrageously high temperature. This is not coolant temp, it is cyl head temp.

Listen to Rockcrawl, I too did mine this way with his advise and the temp gauge works and the fan comes on when it's supposed to. Got my temp sensor from the junkyard off a Cavalier, so I could get the correct three wire plug for it too, just make sure the doner has a gauge and not a light. Replaced the stock 4.9 sensor in the thermostat housing with it. One wire goes to ecm, one wire goes to temp gauge via the C500 connector or the connector under the console, one wire to ground I believe, I don't remember which goes where right now...

Dragon1/Brian

Terminals A and B are for the ECM and terminal C goes directly to fiero guage input. The sensor grounds through the block.
GM 10096181
AC-Delco 213-815
Borg Warner WT3024
CarQuest TX66
Filko CS-43
GP Sorensen 38-5124
Niehoff DR134TA
Napa/Echlin ECHTS4020

Ok, Since I hate to give out wrong info I checked my notes from last summer.
My car is an '86, yours is an '84. It may wire different...

I am using a '2240 Caddy ecm with a '92 4.9 L. motor.

Replace the two wire switch on the thermostat housing with a three wire switch and pigtail connector. Mine came from a junkyard 4cyl. Cavalier with a temp gauge, make sure to take the connector and as much wire as you can get.
pin "A" on the switch goes to ecm "E11"
pin "B" on the switch goes to ecm "E16"
pin "C" on the switch goes to C500 "C2" connection( might be a tan wire). This goes directly to the temp gauge.

Temp sensor in the head is a a thermal switch, it turns on the "hot" light on the dash.
Black wire goes to ground, Green wire to C500 "D3" connection

The fan switch wire comes from C500 "D1" connection(dark green w/white wire) to the Caddy '2240 ecm pin "A11" This turns on the fan when the ecm says to.

Hope this helps...

Dragon1/Brian

Be sure to get a plug with the 3 prong sender from the GTP The computer needs to know what temp the engine is to go into closed loop. This must be hooked up. The third wire goes to the gauge. If I remember right the temp gauge wire is the top of the pyramid if you look at it that way. The Caddy ECM has two wires that come out to run the fans a low and a high. If rockcrawl did the chip for you I think you will hook it up to the low. You should have run the two wires from the ECM to the C-500 connecter and connect to the low fan to the green wire that goes to the fan solenoid to turn the fan on. The temp light is a easy hook-up like rockcrawl said. Just hook the light wire to the head sender and run another wire to ground. When the head reaches a set temp the light will come on the dash. The light sender is not in coolant so it will work without the coolant. Another great idea GM put out.

Rockcrawl, Dragon1 and rroberts thank you very much. +'s for everyone.

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K well I spent the better part of today trying to find a scrapyard that would cut a wiring harness to give me the three prong pigtail. NOne would unless I would pay an obseen ammount. Is there anywhere else I can just buy a pigtail for the sensor?

Thanks.

Got mine from the local Pontiac dealer, I asked for the '99 GTP
pigtail and sensor.
I think the pigtail was around $30 (it's been a while so it could be
a little more or a little less)

Ed

Ed, Perfect thx! I was hoping it wasen't like 100$.

Lance try checking the pick your parts yard...all you need to some time and a set of wire cutters...look for the Cavalier 4 cylinder with a temp guage - locate the sensor, cut the wires harness and maybe while you are at it, remove the sensor (more tools are needed). They are likely only going to charge you $5 at the pick your part for everything - assuming you want to try a used sensor.

Tim

Tim, I spent about 4 hours today driving and searching in the scrapyards. I spent another hour on the phone. Noone would break up a wiring harness for a gtp. The sensor is only 29$ brand new so thats no problem. I guess I'm just gonna see if GM has it. The guy at the scrapyard said for 50 bucks he would cut it. Nowhere else even had gtp's. I found lots and lots of cavaliers of all years with 4cylinder and temp guage but none of them had a 3 wire sensor.

check your email

Tim

[This message has been edited by Mickey_Moose (edited 04-07-2004).]

Sucess!!!! What a great day in the garage. We got the fan all wired up with the new temp sensor and it works great! Thanks so much for the great information everyone!

Sorry I didn't get back to you till today but I'm on vacation and haven't kept up on my emails.
I usually do that while I'm supposed to be working....
Glad you got it working though.
I did find out through my scanner that my temp gage is a little off. It reads about 30 degrees cold, but at least it goes up and down.
If you need anything else, feel free to ask...

Dragon1/Brian