Electric Fans

I've got a 2002 Mazda 626, V6 and I'm starting to have some cooling issues with it (not major yet). I noticed upon startup that the passenger side fan was not operating but the drivers side does. I know that each fan has its own relay so I'm not sure if thats where I need to start or if it might be the temp sending unit. Before I replace the entire fan assembly I'd like to try to narrow it down. Is there a "how to test relays for dummies" for the electrically challanged? I guess I could simply exchange the relays and see if that impacts anything. May have answered my own question? Any guesses?

Are you sure both are intended to run simultaneously? Some cars have two speed fans and some have two fans on two different controls. One fan runs for lower temps and the other kicks in for an assist if things get too hot.

Have you checked your coolant level and for leaks?

You bring up a good point about them both running simultaneously. I honestly don't know if they are supposed to or not. I checked the manual but that didn't provide any information. I also thought that maybe one would kick in when the temp got high but since my wife was driving the car at the time it started to get "warm", I couldn't pull it over to check and see if the fan was running. I did add about 8oz. of coolant (Water Wetter) today at lunch. The thermostat was replaced about 9 months ago as well. The water pump was replaced when the timing belt was replaced about 40k ago.

I have no idea how the Mazda works, but on some Japanese cars with two fans, the second fan only comes on with the A/C.

EvanR wrote: I have no idea how the Mazda works, but on some Japanese cars with two fans, the second fan only comes on with the A/C.

I've also heard that as well but I have not been able to confirm that. I do know that when the AC is on I have not seen the fan come on. I guess I will be switching the relays out to see maybe if that might be the culprit.

it's not that hard to bypass a relay.. a little time and a little common sense with a test light will tell you which wires to jump across to put power to the fan.

I'd start by checking the radiator cap and doing a coolant flush. For bonus points, pressure-test the system. Radiators with plastic end tanks can develop cracks that won't let the system pressurize but also don't leak copious amounts of fluid.

At least one fan should come on with the AC though.

Keith wrote: I'd start by checking the radiator cap and doing a coolant flush. For bonus points, pressure-test the system. Radiators with plastic end tanks can develop cracks that won't let the system pressurize but also don't leak copious amounts of fluid. At least one fan should come on with the AC though.

The plastic overflow reservoir tank has been replaced twice in the past 2 years. A coolant flush was done at the last oil change about 3 weeks ago.

My BNL said disconnect the sensor wires going to the temp sending unit and turn key to on position. If both fans come on they are good. If not, then I need to do some more troubleshooting.

triumphcorvair wrote: IIs there a "how to test relays for dummies" for the electrically challanged?

YES.

The overflow tank might be fine, but what about the end tanks of the radiator itself?

Did you say one comes on at start up ? This would only be when the AC is on. Other wise, a relay is stuck.

slantvaliant wrote:

triumphcorvair wrote: IIs there a "how to test relays for dummies" for the electrically challanged?

YES.

Awesome video! Placed these instructions in my toolbox. Thanks!

iceracer wrote: Did you say one comes on at start up ? This would only be when the AC is on. Other wise, a relay is stuck.

a bad ecm or temp switch can cause fans to either be on all the time or never come on, too.

Keith wrote: I'd start by checking the radiator cap and doing a coolant flush. For bonus points, pressure-test the system. Radiators with plastic end tanks can develop cracks that won't let the system pressurize but also don't leak copious amounts of fluid. At least one fan should come on with the AC though.

The fan on my MX-3 stopped coming on after the engine swap. I thought it might have something to do with the KLZE computer. Disconnecting the sensor makes it run all the time so the engine doesn't overheat. However... there is a crack in the water neck under the rad cap. Could that be the culprit?

I can't see that stopping the fan. If it's in the unpressurized part of the neck, it shouldn't be an issue.

I wasn't recommending checking the rad/cap because the fan may or may not be working. I just see more cracked rads and bad caps than I do bad fans, so I tend to suspect them first when there's a cooling problem.

With the instructions in hand to test the relay, I opened up the fuse box and according to the fuse/relay diagram on the fuse box cover, it didn't show a fan relay. I checked the fuzes and they are good, Looked on the NAPA online store and it shows a fan relay for this model of car.???

Check in the area between the two fans. It may not look like the usual relay you find in the fuse box.

novaderrik wrote:

iceracer wrote: Did you say one comes on at start up ? This would only be when the AC is on. Other wise, a relay is stuck.

a bad ecm or temp switch can cause fans to either be on all the time or never come on, too.

True. The AC part is easy to check. Make sure it is turned off. Fan still runs ? Look farther as you said.

Late model Escorts have a Constant Control Relay Module CCRM. This often is a problem when the fan relay melts. It is located in the engine compartment. Your Mazda may have something similar seeing the relationship between Ford and Mazda at the time.

As much as I loved the KLxx motors the electronics Mazda put on them were horribly over done. When my fans went out I just wired my own simpler system in. I still don't understand why they put 2 cooling system openings on them for 2 rad caps to fail....

I would start by putting power to the suspect fan directly and see if it runs. Then work back from there.

dean1484 wrote: I would start by putting power to the suspect fan directly and see if it runs. Then work back from there.

This is one of those "Why didn't I think of it moments". I guess I got so wrapped up in overthinking this I didn't think of the obvious! I applied power to the fan and it works! Now I just need to work back from there as stated.

ThePhranc wrote: As much as I loved the KLxx motors the electronics Mazda put on them were horribly over done. When my fans went out I just wired my own simpler system in. I still don't understand why they put 2 cooling system openings on them for 2 rad caps to fail....

This.

However the second fan should not kick on until a/c is on AND the second thermoswitch is flipped. If it's not getting hot enough and both requirements aren't satisfied, the fan won't come on.

Mazda used test connectors on most of these cars. Do you have a brown open connector with two spade connectors in it? If so, that'll test the circuits of fan one and fan two. (In theory.)

But really, just buy a programmable thermoswitch from Summit and wire it directly in to the fan. Easier and more reliable.

Mazda used test connectors on most of these cars. Do you have a brown open connector with two spade connectors in it? If so, that'll test the circuits of fan one and fan two. (In theory.)

But really, just buy a programmable thermoswitch from Summit and wire it directly in to the fan. Easier and more reliable.

I dont see the connector that your referring to, but that doesnt mean its not there, I found the fan relay, just having a heck of a time removing it from it housing, Its located on the outside of the fusebox. I'll run it by NAPA and see if they can get it out. My luck the last 2 weeks has been rotten, I don't want to take a chance and break it or something,