Un-bypassing radiator fan relay

[btoran]

either my car came with the radiator fan relay bypassed, or the relay is defective. ragardless, as soon as i turn the key in the ignition to the "on" position, the radiator fan comes on and stays on until i turn the car off.

if the bypass was intentional, i'm hoping it was not because the engine was frequently overheating. i don't think so, because the temperature never climbs above 130, which i verified with a laser heat gun.

where should this relay be located on my 1975? and if it has been bypassed, is it as simple as ensuring the wirring goes first to the relay and then to the radiator fan? does anyone have any pictures that might be helpful?

thanks in advance for your assistance.

[4uall]

This may help

http://www.artigue.com/fiat/

[majicwrench]

Once "unbypassed" make sure temp comes up. Car will run better, last longer, and get better mileage if temp get to 190 or so.
Keith

[fiatmike124]

I would unplug one of the wires to the thermal fan switch on the radiator. If the fan still runs than the temp switch is being bypassed. If it cuts out then the switch is not bypassed but possibly defective. The switch just completes the ground circuit to the fan and should be normally open below 190 I beleive.

[btoran]

Everyone - A really strange thing happened last night. I went home and decided to mess around with the fan wiring. but BEFORE i did anything, i turned the ignition key and for the first time ever, the fan DID NOT come on. it's like the car knew i was after this fix. cool, thinks i, the car fixed itself. nope. i let the car warm up and the temp hit 190, then climbed higher and eventually started to overheat. the fan didn't come on at all. so i went from one extreme (fan always on) to the other (fan never on). i then carefully checked the connections and this is what i found:

this picture shows the connection directly to the fan. i removed the connection and stuck the probes of a multimeter into the connectors and found no current at all. i wanted to remove the wires from the plastic connector and check them individually, but i'm not sure how the wires are held in. there is some of the green (hot) wire exposed just by th eplastic connector and i tested it and a known, good ground with the multimeter, but there is no voltage there. next, i visually checked fuse A and tested it by successfully sounding the air horn, so fuse A must be good. i traced the black wire from the connector back to a ground on the side of the engine compartment. i cleaned all contact points for this ground. the green wire disappears into a bundle of wires. the yellow wire with black bands (lets call it yellow1) i traced back to one of two connections that were unused and taped together.


these are the two unused yellow wires that were taped together. the one with the black band (yellow1) goes back the the connector on the radiator fan (as you can see in the previous picture). the other yellow wire (the one with the solid stripe - let's call it yellow2) disappears into a bundle of wires. i tested these unused wires and found they carry 12 volts.


i then disconnected the wires from the first picture above and instead, connected the unused yellow wires from the second picture. as soon as i did, i heard a clicking sound coming from near the engine. each time i disconnected and reconnected these wires the click occurred. i thought this was a good sign as it could be a relay closing, because the engine had now cooled down. so i fired up the engine, let it warm up and expected the fan to come on at 190 degrees. no such luck. the temp shot past 190 and i shut her down as she was just starting to overheat. the clicking was coming from the black relay just north of the blue wire in this picture.


btw, the artigue site has lots of wiring diagrams, but none for 1975.

my questions:

1. how are the wires connected in the plastic holders? i'd like to know so i can carefully remove them and see if i have 12 volts across the original wires connected to the fan.

2. what are the two unused yellow wires for and what is clicking sound i hear when i connect them directly to the fan?

3. how SHOULD all of these wires be connected properly for the fan relay to work as planned and where is the elusive fan relay?

4. bonus questions......below is a picture of the relays. a) what is the round black thing on the left by the arrow? b) is there a relay missing where the blue wire is?

[seabeelt]

Look at the Artique wiring diagrams. The colors may be somewhat different for the different years, but I believe they all use the same fuse. Once you know the fuse ( 9 or 10) Which engages the coil on the relay. You can trace that wire to the relay . There should be an additional wire from the fuse box ( fuse 1) that supplies the actual power through the relay to the fan. Pin 87 on the relay should go to the fan. Relay pin 86 goes to ground, relay pin30/51 should be power ( on all the time) from fuse 1. Relay pin 85 should go to fuse 9 or 10.

[btoran]

an update.....

i found an old thread about the switch at the bottom of the radiator going bad and a quick test of shorting between the posts of the switch to turn the fan on. i tried leaving the original connector on, turning the ignition switch to the on position, and shorting between the posts of the radiator switch. the fan did not come on. does this mean the switch itself is bad? btw, i also tested the leads going directly to the switch on the bottom of the radiator and i get no voltage. kick on. a bad

[seabeelt]

The way the fan works, with or without the relay is that voltage goes to the fan. The thermal switch at the bottom of the radiator completes the ground circuit. Switch open ( temp less than 185 or so) fan is off. Switch closed ( temp above 185 or so) completes circuit path to ground, fan runs. Most folks are by passing the thermal switch and manually switching to complete the ground circuit. Some cars are set up so that the fan will run even with the ignition switch off to help cool the cooling system down. Early cars did not do this, I know my 71 does not, but my 78 did. So easy test. Plug the wires back into the fan. You should have 12 v on either wire. You should also,have 12 to one side of the thermal switch ( wire from fan to thermal switch). If you ground that wire, fan should run. If not , bad fan motor.

If your car has a relay, it should operate like my 71. Fan does not run with key off. If your car has no relay, it should operate like the newer models and run regardless of key position. If it has the relay, key must me on to energize the relay.
R/

[btoran]

Thanks for your help. It's working now.

I took those two previously unused yellow wires and connected them directly to the switch on the lower part of the radiator. when the temp approached 190, the fan came on, cooled things down a bit, and then shut off. it successfully cycled this way for a few minutes before i shut things down. i figured that when i connected these wires to the fan itself previously and heard a clicking, it was a relay closing, so the yellow wires must have been meant to open and close some relay. i think i just got lucky that it was this one.

in re-reading your posts, i think i figured it all out.

the car came with a bypass in place. instead of the yellow wires being connected to the radiator switch, another set of wires were run directly there. literally, over the last two days, the power to those direct connections stopped. i'm also doing a center console radio project and i must have jiggled something near the radio that stopped the juice from flowing to the bypass.

the question is why was the bypass put in place if the radiator switch, relay, and fan are all working as designed?

[seabeelt]

Could have been a lot of things. Mostly the cooling system is not burped completely causing a small air pocket. If there is an air pocket, the car has a tendency to overheat as the coolant temp never reaches the thermal switch cut in temp at the thermal switch location. So folks jumper the thermal switch out and run the fan when they think the car is too hot

If the cooling system is burped properly - no air pockets - and the thermal switch is good, radiator has no blockage and the thermostat is working properly, there is no need for a bypass switch. That said, some cars will have the temp creep up in traffic. Hence the bypass switch again, but I have found that if you increase rpm just slightly, you can circulate the coolant enough without resorting to a work around. Just my 2 cents.
R/