OK, all you fan switch gurus, I need some help with this one. Here's the problem I have with the '86 GT:

1. Radiator fan will not come on when the car gets hot
2. Circuit is good. Fan runs when the fan switch connector is grounded out.
3. Fan runs when A/C is on.
4. New fan switch installed 'dry' - no pipe compound or teflon tape used.
5. New fan switch connector installed.
6. Temp gauge accurate -tested with resistors on green/white wire.
7. Temp gauge needle gets into the red area without the fan starting. I turn on the A/C, and the temps will cool to 220.

Any ideas? Why won't the fan come on? Is there something I've missed? Hate to keep getting the car hot just to test the fan switch... I do not want to install a manual fan switch - I want to fix this problem, not get around it.

Thanks,
Larry

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One-owner '88 coupe 188,000 miles, Daily Driver
Sharon's '86 GT, On The Road Once Again!

[This message has been edited by SC Coupe (edited 08-21-2004).]

quote Originally posted by SC Coupe: 2. Circuit is good. Fan runs when the fan switch connector is grounded out. 4. New fan switch installed 'dry' - no pipe compound or teflon tape used. 5. New fan switch connector installed.

I think you just missed the answer in your own diagnosis. The new fan switch must be bad. If you ground the wire going to the fan switch and the fan runs, you've pretty much nailed it haven't you?

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RickN
White 88GT 5spd
White 85GT Auto

With the A/C turning the fan on continuously the temperature should read whatever the thermostat temperature is, 195° stock for instance, and stay there. If you're reading 220° with the fan on continuously I would say your guage is off. Do you have a way to measure the actual temperature of the coolant? If you have WinALDL and an interface cable you can see what the ECM see from it's own temp sender.

JazzMan

The OE type switch won't turn on until 235. A more accurate test is probably to scan the ECM's temp sensor. That one will report directly in degrees.

Concentrating on the fan switch alone may be leading you away from more important things. Generally... If the car is moving any air thru the radiator at all, most will stay cool without the fan. (This applies to most cars on the road.) If the cooling system is working right, you shouldn't need the fan on full time.

Just how fast is the temperature climbing? If it shooting up at every traffic light, you could have more problems than the fan switch. Like a mashed pipe under the car or a partly blocked radiator. There are a bunch of things that could be contributing to heating problems. Could be one large item or several small ones working together. Even seemingly small things like missing trim/body parts can affect it.

Mashed pipes are a really comon problem that few people seem to check for. If the pipe is even a little crushed it can have a major effect on cooling the engine, especially on a v6 but even the L4 will feel it.

Since fixing the mashed pipe on my L4, the only way it will get hot is if it is running parked with the hood closed. Just opening my hood now creates enough convection that the thing won't turn on the fan for a long time if at all. (And the 87 L4 is factory programmed to turn on at 225.)

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The only thing George Orwell got wrong was the year.

The Ogre's Fiero Cave (It's also at the top of every forum page...)

OK. Here's some answers to the questions, and an update.

I don't have WinALDL or a scantool to check the coolant temp. Wish I did. I did check the engine temp sending unit with resistors. Gauge reads 100 deg. @ 55 ohms, and just barely above 260 deg @ 1470 Ohms. I'll ask a mechanic I know to check the coolant temps against my gauge with his scanner next week... The temp gauge sending unit is new.

The new, stock 'TFS1' fan switch is the third switch tried on this engine in 2 weeks. The engine temperature gauge climbs slowly - I 'test' the switch by driving the car 'til it comes up to temp and then letting it idle in Park (it's an auto) as the gauge needle slowly climbs towards the red. Last week, the fan would come on briefly (for only 10-20 seconds or so), and only when the gauge needle reached the red area. This was with the TFS1 switch installed. I was concerned about this as you might understand..... I replaced the fan switch with another that I had on the shelf, and 'tested' again. The gauge hit the red zone, but no fan. I turned the A/C on and cooled the engine down. Next day, I put the first fan switch BACK in the car and 'tested' again - no fan.

According to the catalog at the parts store, the TFS1 switch closes at 236 deg and opens at 224. They had a TFS8 switch that closes at 220 and opens at 204. I bought and installed the TFS8 this afternoon. Again I drove the car to warm the engine and transmission (A/C off), the temp gauge needle finally started going above 220, I parked the car and let it idle, and finally the fan came on. The temp gauge needle was about 2 ticks away from the red area when the fan started. The fan continued to run and engine temps cooled to around 220. I drove the car a while, went back home and let it idle in the driveway. The temp gauge fell to just below the 220 mark. After a few minutes, the fan was still running. I wasn't patient enough to wait and see if the temps would go lower, or if the fan would shut off, and turned the ignition off.

So, for now, it seems that I don't have to worry about the fan not coming on, but it just might run constantly once the engine comes up to temp...

[This message has been edited by SC Coupe (edited 08-21-2004).]

Hey sc coupe my car does the same thing and i can't figure out why it won't work on its own. i grounded out the connector and the fan comes on ,installed new switch and let engine get way hot and fan didnt come on . I have given up and just drive with the a/c switch on (i have no a/c compressor installed). I will eventually install a manual switch in the car to controll it without a/c on.

Your guage is wrong. Turn on your ignition switch but do not start the engine, (do this test when engine is cold) The temp gauge should read 100. or put a 55 ohm resistor in line with the green and white stripe wire and it should read 260. I have not been able to find a 55 ohm resistor so I use a 33 and 22 in series. If it does not read to these specs, then you will have to remove the hand and replace correctly. this is common with the Fiero due to the fact that the hand pegs when starting the engine, and it moves on the shaft. I use a TS-85 sensor by Standard Automotive and it is perfect. the fan comes on at 222 and off at 200. Hope this helps.
Don

Driving around recently with my code scanner attached to the ECM showed that my '85GT is running 20deg hotter than the temp guage is showing. So, don't use the dash guage to make any decisions until you've had it verified/calibrated.

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RickN
White 88GT 5spd
White 85GT Auto

I mixed these up:

quote Originally posted by SC Coupe: Gauge reads 100 deg. @ 55 ohms, and just barely above 260 deg @ 1470 Ohms.

I meant.....Gauge reads 100 deg. @ 1470 ohms, and just above 260 deg @ 55 Ohms.

I'll check that gauge against a scan tool next week. At least I know it won't overheat. Just drove around the local area for about 20 minutes and the temp was steady. Cruised to the beach and then into the stop-and-go traffic 'in town'. Temp gauge did not fluctuate much, and the fan never stopped running. Think this 204-200 fan switch would work better (shut the fan off once in a while?) if I used a 180 degree thermostat instead of the 195?

Thanks and positive ratings for all the help! I'll keep you posted on how this all works out...

Larry

[This message has been edited by SC Coupe (edited 08-21-2004).]

Installed a 180 deg thermostat and the fan does cycle on and off in traffic or sitting at idle. If I use the rating on the fan switch as a guide, the dash gauge is reading somewhere around 20 degrees high...

Sounds good!! Temp sounds a bit low, but at least it isn't kicking on and off anymore.

Matt J

[This message has been edited by MRJ (edited 08-23-2004).]