engine cooling fan

[jsupple90]

I think it is plugged in.....unless I just don't know where the fan switch is located?

[blkfordsedan]

The fan temp sensor is located in the thermostat housing right by the distributor. The sensor is just a basic thermoswitch that is normally open. When the engine gets up to 207*F the thermoswitch closes, completing a circuit from the "prong" where the wire attaches to the housing body of the sensor (grounds it out). The wire that plugs into the sensor is just the ground wire for the control side of the fan relay, which is located behind the driver's side headlight. This allows current to pass through the control side of the relay, causing the normally open switch inside the relay to close and complete the power circuit to the fan motor. If the fan runs all the time, the sensor is either stuck "closed" or the switch inside the relay is stuck in the closed position. You can check the sensor by setting your multimeter on "continuity". With the engine cold, touch one lead to the wire prong on the sensor and touch the other lead to the body of the sensor. It should be an open circuit (no continuity). If there is continuity, the sensor is bad. If you have the opposite problem and the fan never turns on, you can bring the engine up to temp (207*F) and perform the same test. You SHOULD have continuity above 207*F but NOT below 194*F. If you can not get the temp up to 207*F by driving the car, you can remove the sensor and hold the threaded end in boiling water. If the sensor checks out, then the relay could be stuck closed. It is also possible if the sensor is bad, causing the fan to run all the time, the relay contacts will also begin to stick closed making it also fail. I believe a sensor for a 323 will fit, but I THINK it's opposite in function (normally closed). In theory, you could use a 323 sensor along with the fan relay from a 323. Also, you could unplug the wire from the bad sensor and hook it up to a simple toggle or rocker switch in the dash (since it's just a grounding device) and convert it to manual operation. Hope this helps

[blkfordsedan]

Sorry, my mistake. I checked an old Haynes manual I had for my old Protege/323. The procedure for checking continuity on the fan switch sensor is the same as on a Festiva, so I guess a sensor for an early 323 would indeed work. It would however appear that the relay is different (more complicated).

GenevaDirt mentioned that the temp sensor had to be plugged in or the fan would run anytime the key is on. The Haynes manual says the same thing, but I don't quite understand it. If the sensor only completes a ground, then unplugging it would not create a ground situation, but rather keep the fan relay from ever turning the fan on. I figured it was simply a misprint in the book. I have only basic electrical knowledge, can someone with more electrical expertise explain it to me?

[bobstad]

hope this isn't copyright infringement?

excerpted from a thread
<http://autorepairexchange.tribe.net/thread/c5893909-8f7c-449a-bb22-16dc0e8cd301> I began yesterday in the web site <http://www.tribe.net> where I moderate ORNITHOLOGY tribe, for fans of genius alto saxophonist Charlie Parker's jazz music.

I thought the second responder's ideas interesting...I have a relatively new after market all metal a/t radiator and don't think there likely any blockages; and went to the trouble anyway of having the whole system flushed, or at least the contemporary equivalent which involved recycling of the motor's coolant as well as an additive after a chemical treatment of the innards of the cooling system.(I'd still more trust the violent back-flushing technique I'd been used to as a gas station attendant in '70 when they still mostly all had lube-rooms and no one had thought of self-service pumping except the occasional familiar in a hurry and/or gas theft)

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'91 Festiva cooling fan activation switch? topic posted Yesterday, 1:46 PM

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Re: '91 Festiva cooling fan activation switch? Yesterday, 2:43 PM

a generic thermoouple switch, good for any number of different vehicles, might possibly come with a different setting than the one specfically required for your application.

Sometimes I have found switches and sensors at used car parts yards, that if you pulled it yourself, cost almost pennies in comparison to retail.

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Re: '91 Festiva cooling fan activation switch? Yesterday, 3:25 PM

I'm a really big fan of keeping things stock. Not that things can't often be redesigned in a better way, it's just that usually when I see things in my shop that have been 'improved', they usually have several design flaws on their own such as improper connections, bad placement, components that were never really designed to work in very hot or heavy vibration environments, or to carry the kind of loads that things like fan motors require. But, get an automotive brainiac or engineer involved and you can improve the system.

Besides all that though, it sounds like you are assuming the switch is bad based on other peoples common failures. I looked at the wiring schematic for this and you could also have a bad 20 amp Cooling Fan Fuse or the 10 amp Meter Fuse, both located in your ignition panel fuse block, either one will cause the relay not to function. You could also have a bad Fan Relay, located behind your left headlamp that has failed. If the relay and/or 20 amp fuse has failed, it could be the result of you fan motor aging and drawing excessive amperage through the system. Obviously the fuse would be much cheaper than the switch, the relay is pretty likely cheaper too.

There are lots of different part manufacturers, if you must go to Napa for the switch I would opt for the better one. But personally, I would still get the Ford one. It's probably cheaper than the expensive Napa one, and factory parts are continually going through improvements in design. Somebody (besides Ford) is manufacturing these for Ford, if they have a high failure rate you can bet that Ford has put a lot of pressure on them to improve their design.

Ford hates repeat failures as much as you do.

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Re: '91 Festiva cooling fan activation switch? Today, 8:43 AM

One other thing to check if you have the access, is to see if hot water is actually reaching the switch...

I have seen a number of unmaintained cooling systems that have obtained enough internal blockage in the radiator to prevent hot water from actually contacting the pickup of the thermoswitch.

Have seen it on several occasions where the flow through the radiator was maintained only throughout half of the designed area. You will have to remove the front grille or obtain access to the front of the radiator to check this.

It works best if you start with a cold engine. Block the wheels, set the emergency brake and leave the vehicle in park. Then I like to use a non-contact infrared thermometer to 'scan' the surface of the radiator as it warms up. one looks for hot and cold spots. Not everyone has a non-contact thermometer, so providing you start with a cold engine and let it warm up slowly, you can use your hand to feel for cold and warm spots. Be sure there is nothing in the area you can get your hand caught on. You will know if there are plugged places if you cannot hold your hand to one area, while another area stays cool.


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[getnpsi]

cool posts. Moral of the story: today you probably dont need your fan, but one day you will. Take off the components and test them. Remove thermo housing and inspect for corrosion and blockages. The festiva part has pretty tiny passages. I was going to add that housing to my aspire so i could run an aftermarket gauge, and mine was too junky to trust. Remember my festiva came to me free because of a head gasket failure. Erring on the side of caution i decided not to put any cooling system stuff onto a running car from a bomb

[bobstad]

Ta Da !!!!

...after removing everything, but the starter; I got the fan back in and pulled the connector to the thermostatically controlled switch and now have a functional fan::fred: Though likely I'll wire in a dash switch to manually over-ride the dysfunctional(evidently) thermostatically controlled unit since the expense/rigmarole of replacements sounds discouraging/hypothetical.

Anyone have a "fave" way of doing that?(I'd get an old commercial laundromat dryer "start" control since then I'd have me a great second horn button whensomever I did get the thermo-thingee...):coffee2:



UNNECESSARILY COMPLEXITIES: (could've simply removed contact from thermo-thingee as needed) FAN REMOVAL & REPLACEMENT; RADIATOR REMOVAL & REPLACEMENT;(could've crimped old one-SAVED!) BATTERY MOUNTING BRACKET REMOVAL & REPLACEMENT; AIR-INDUCTION PHLEGM CONDUCTOR REMOVAL & REPLACEMENT; BATTERY REMOVAL & REPLACEMENT, HOSES REMOVAL & REPLACEMENT, including TINY ONE REMOVAL & REPLACEMENT next to thermo-thingee, AND EXERCISE OF special VOCABULARY appropriate.(REMOVAL & REPLACEMENT not practically feasible...)