rad fan switch failing???

[AVMECH]

New to Fiat spiders, I got a 1981 spider2000, fan seems to turn on to late and off to soon.

Car runs at good temp, just below or at 190. but when sits at an idle, creeps up and fan dosen't engage untill needle goes just past the zero in 190. Seems to hot to me. Fan shuts off when needle is betwee 9 and 0 in 190. Seems like it should run longer.

On a side note, temp indication does jump up a bit when headlights are turned on, figure it's inducing from headlight circuit into sender wiring. Don't think this is a big issue as the temp seems normal when running with headlighs off, and it really only goes up a little.

What I've done to try and remedy this is a fluid change with good (I think) bleed. Followed directions given by international auto, took alot of time doing it and massaged all hoses till all bubbles stopped. Yes, I had the heater open. no, I did not drill a hole in the thermostat, but I did fill the lower radiator hose to top, then installed thermostat housing, then continued with bleed. Lower hose seems to get hot at appropriate time, heater works, just seems like the fan is delayed in turning on and early at turning off. Is this a sign of a failing fan temp switch? Anyone had this trouble?

[azruss]

I bought my first Fiat because of a classmate of mine who had Abarths. He gave me some very sage advice. "Dont pay too much attention to your temp gage or it will drive you to insanity." sounds like your system is working fine.

[jsab]

I agree with azruss, I've got 4 spiders and they all do that.

[vandor]

> when sits at an idle, creeps up and fan dosen't engage untill needle goes just past the zero in 190.

This is normal, but if it bothers you there are fan sending units which activate at a lower temp (by about 10 degrees).

http://www.autoricambi.us/cgi/commerce. ... =CO2-010-Z

>On a side note, temp indication does jump up a bit when headlights are turned on, figure it's inducing from headlight >circuit nto sender wiring.

More likely it's poor ground for the gauge.

>, took alot of time doing it and massaged all hoses till all bubbles stopped.

Did you put a bleeder T in the upper heater hose? Makes it a lot easier.

[So Cal Mark]

those temps are normal, the fan will only drop the temp about 10 degrees. You can always replace the switch with an adjustable controller if you want to dictate on/off temps

[AVMECH]

I just want to calrify, i don't mean just past the zero like needle is in the zero and just past the begining, i mean like Goodbye Zero, creeping toward the red now. If that is normal, I may try an aftermaket switch. these things really run that hot before the fan comes on?

[vandor]

I just want to calrify, i don't mean just past the zero like needle is in the zero and just past the begining, i mean like Goodbye Zero, creeping toward the red now.

No, that's not normal. The fan should come on around 195F, maybe 200F, so the needle should be just past vertical.
Be sure your lights are off, tho

[AVMECH]

No, that's not normal. The fan should come on around 195F, maybe 200F, so the needle should be just past vertical.
Be sure your lights are off, tho

That's what I thought, seemed to hot to me. Yeah, lights are off and that's what it does. Looking more into it, I noticed that the car makes a bit of a growling, mabey more scraping noise around the water pump and the pulley has a wobble to it.
I also noticed last nigh, if I'm sitting at an idle, and watching the temp go up, I can lower the temp by giving it gas and holding RPM at aboput 2000 or so. I would think that would make the temp go up unless I had a pump that wasent pushing water fast enough at idle.

My thoughts are the fan switch would probably work or not work, and that's that. The thermostat opens up at the correct temp, as that is controlled by the hot water coming out of the cylinder head. the fan dosen't get hot water till the water out of the head makes it's way to the bottom of the radiator, which is limited by how fast the pump can pull it up the lower rad hose, and as the pump is wobbley and inefficiently moving water, is causing a delay in the fan actuation.

Am I crazy or does this sound logical? Has anyone run into this? I really don't think this is a problem caused by incorrectly bleeding the system. It did this when I first got the car, and it is still doing it now after a fluid change and bleed.

Unless someone has a better suggestion, my next step will be to drain the radiator again, saving the coolant in a jug. Pull the switch and measure when it is opening in a pot of hot water with a meat thermometer in it. If the switch checks good, I will drain the block saving the fluid, replace the pump, and put the fluid back in and rebleed.

Anyone have any thoughts? I'm pretty strapped for cash right now and don't want to dump money on shotgunning parts, I would rather change only what's broken.

[vandor]

Pumps usually fail by leaking, not by pumping less water, unless corrosion inside the engine is so bad that the impeller has started disintegrating. However, if it is the shaft that is wobbly, and not the pulley, then it needs to be replaced.

Your plan of action sounds good, but I'd filter the coolant before putting it back it, as it can pick up a lot of dirt draining down the side of the engine.

[AVMECH]

I talked to international auto and they are out of switches until jan 1 anyway, so I'll leave as is for now. I need to keep it together as an emergency back up car so I don't want to find that switch bad and have to wait till jan to drive it again. (not going to go through draining and filling more than one more time. It's a messy PITA) I'll update this thread when I find a solution, but it won't be next week. Thanks for all the replies.

[So Cal Mark]

Have you checked the temperature at bottom of the rad where the switch mounts? I've seen them with build up of debris that insulates the switch. The fan should turn on when the needle is in the 0 of 190. From your description it sounded like that was the scenario.

[courtenay]

Try disconnecting the wire attached to the temperature sensor in the block closest to the radiator. There are two sensors in the block that go to the gauge. One measures the actual water temp and the other "spikes" the needle. A few of us have had a similar issue and found that the problem was with the "spiking" sensor. If it is, in fact, the problem, you will find that after you have disconnected it, the gauge will read as it should and the fan will come on as it should.

[AVMECH]

Courtenay, I read about that as I was searching for solutions in past posts. After disconectiong the sensor on the head between the spark plugs, the reading started bounding erraticly, so I plugged it back in, figuring all the sensors were working. I did manage to break the rubber boot in the process. So Cal Mark, how would I check the temp at the bottom of the radiator? A thermometer on the metal? Would that get close enough? Not going to open that drain plug while hot, the only reading I would get is AHHHHH!! OOOWWWWW!!! Sorry about my description, I realized it was a little misleading after I read it agian. Temp is 190 or less while driving. When sitting at idle, creeps up past the zero in 190, and closer to the zero than the red, fan turns on. takes temp back to about between the 9 and 0, and turns off, letting temp creep back up. Winding up the engine for a bit slowly brings the temp back down.

[courtenay]

You can use an infrared thermometer to check the temp of your rad, hoses and block at various points. It's one of those gizmos that you point at the spot you want to measure and it gives you the temp. However, it doesn't sound like your car is overheating anyway. Going a bit over 190 is not necessarily a bad thing. The needle actually getting into the red is.

[vandor]

> After disconectiong the sensor on the head between the spark plugs, the reading started bounding erraticly,

That's not normal. Are you sure the wire connector was not laying on the head and grounding?

> I did manage to break the rubber boot in the process.

They are available new.