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Discussion Starter · #1 ·
HI Guys, just bought this 1993 MX-6 V6 and its a great car runs like a top but has this weird cooling fan problem.

When I start the car all is fine till the temperature gage shows half way then the Cooling Fan comes on never to go off again while the engine is running.

I think the cooling fan should not come on til the temp guage is somewhere near the red part of the gauge, then the Cooling Fan should come on, run a while and shut off again. Well mine dont do that it comes on when the temp is half way and keeps runnin.

Has anyone got an idea if there is another temp sensor other then the one used for the motor management, which is in the middle of the engine by the distributer belt of the V6.

There must be another sensor that is giving the signal to turn on the cool9ing fan when in normal operating temperature. OR could this be an emergency ON due to missing signals to the ECU??

If anyone here can help me, please thx.

Rob
 

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The cooling fan is coming on at the correct time. On our cars, the temp gauge never goes beyond the halfway mark unless there's a problem or in extreme situations. Your only problem seems that the fan doesn't turn off.

Our cars have a smaller a/c fan that comes on when the a/c is switched on. Make sure your a/c is off and see if you have the same problem. By the way, the front window defroster setting on the heater controls makes the a/c come on even if the a/c button isn't pressed.

Post back with results.
 

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Discussion Starter · #3 ·
The cooling fan is coming on at the correct time. On our cars, the temp gauge never goes beyond the halfway mark unless there's a problem or in extreme situations. Your only problem seems that the fan doesn't turn off.

Our cars have a smaller a/c fan that comes on when the a/c is switched on. Make sure your a/c is off and see if you have the same problem. By the way, the front window defroster setting on the heater controls makes the a/c come on even if the a/c button isn't pressed.

Post back with results.

Ok Car does have A/C switch on the dash but does not seem to function no green led goes on, also no a/c cooling fan in front of radiator, only one fan on drivers side of the radiator, passenger side of radiator does NOT have a FAN!!!

Tried all window defroster settings, but non influenced the operation of the Radiator FAN.

So end result NO changes from original discription RAD. FAN wont shutoff at all when car being driven/engine running.

Thanx for responding,

Rob
 

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Since there's no second fan, then perhaps the ecu is responding to that by keeping the main fan on at all times once the car is warmed up. I've never heard of this problem before so I don't know what other advice to give.

Paul
 

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Discussion Starter · #5 ·
Since there's no second fan, then perhaps the ecu is responding to that by keeping the main fan on at all times once the car is warmed up. I've never heard of this problem before so I don't know what other advice to give.

Paul
Hmmm Might be a ECU problem not shutting down, on the other hand does the ECU get a seperate input for start fan temp and STOP Fan temp, i wonder?

Rob
 

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Discussion Starter · #6 ·
Looked at this problem some more and tested the ECU by putting it in another car, and the ECU is good/fine. So the problem must be in the wiring somewhere.

Does the standard car ECU use any signals from A/C pump to the ecu??

Does anyone know which signals are used to run the cooling Fan??

What i have figured out sofar is that the 3 relays which steer the two FANS one for cooling and one for the A/C, supply the PLUS + voltage for the Fan motor and the ECU supplys the Negative voltage for the Fan. And also the relays steer the voltage in such a manor that the low voltage gives a slow FAN speed, and a HIGH voltage give a HIGH fan speed.

Now to figure out a way to fool the ECU to think all signals are correct.


Rob
 

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Discussion Starter · #9 ·
keep having error 69, come back after resetting the CPU. Ok this has to do with the second temp sensor in the waterinlet pipe by the second radiator cap, on the left side of the engine.
It seems that when this second tempsensor is not present the computer give a signal to the electric radiator fan to stay running as long as the engine temperature is at normal operating temperature or higher.
The above would explain why the 93 models can have the always running FAN problem.

I will be getting a sensor installed soon and see if the instalation of the second sensor will solve the always on fan problem.

To Be continued

Rob
 

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Discussion Starter · #11 ·
Well I installed second sensor but to no avail, I reset the ecu and I still have the fan coming on at 1/2 temp guage reading.

Does this mean that sometime somebody changed the ECU and this is why i have the problem?

Anybody program these ecu's and can tell me what else can be done??

Thanks for any help

Rob
 

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Discussion Starter · #12 · (Edited)
Checked the wiring to second sensor, one of the wires was severed about an inch from the socket. Repaired it and reinstalled the Black sensor (second temp sensor) and low and behold it works.
Now when my car gets to normal temp no more fan.
Well now i removed the sensor while the engine was running and there the fan went again blowin its fool head off, I reconnected the black sensor again and fan quit runnin again, so all is normal now.

Only one thing, my waterinlet housing does NOT have a location where i can install/screw in the second temp sensor, it has the flatspot where the sensor hole can be drilled and tapped.

I am gonna try one more thing before I drill and tap the waterinlet housing and that is, another eprom in the ecu.

I heard that if you have a 1994 engine or later in a 1992 or 1993 mx6 then you should be able to use a 1994 eprom in your 1993 ECU and have the fans work like the 1994 version. IOW fans are then controlled by the GREEN primary temp sensor on your car, that is the way it works on a 1994.

So I am gonna try that first, if that works, then I wont have to Dril and Tap my water inlet housing/casting and all the control will be done by the green temp sensor, AND that will eliminate the need for the BLACK temp sensor and its wireing altogether.

Rob
 

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92 and 93 models aren't the same, ecu problems shouldn't be transferable to solve this problem.

you can test your route of getting mods done to the ecu but there is a real issue if you have no factory placement for a factory sensor that all 93-97 models should have. if your car came with A/C and needs that sensor to control the fans then you should have a mounting place for it. If your car doesn't need that sensor and doesn't come with it from the factory then there is an electrical issue going on that can potentially result in other systems failing later on.
 

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Discussion Starter · #15 ·
92 and 93 models aren't the same, ecu problems shouldn't be transferable to solve this problem.

you can test your route of getting mods done to the ecu but there is a real issue if you have no factory placement for a factory sensor that all 93-97 models should have. if your car came with A/C and needs that sensor to control the fans then you should have a mounting place for it. If your car doesn't need that sensor and doesn't come with it from the factory then there is an electrical issue going on that can potentially result in other systems failing later on.
Hi mx6girl93,

I think my major prob is thats someone swapped engines in the car and did not swap wiringloom and ecu, as I call it a halfaserd job.
So now I am left with the pieces to fix it, which as I said has been done to a point. I used the existing wires with the black socket which is for the 3rd temp sensor. Hooked up an original Black sensor to it and the fan stopped running.
So now before I go and tap and dril the water inlet pipe casting I thought i'd try it wit an eprom before I did the work to permanently mount the 3rd sensor, as was done in the orig. 1993 versions.
Over last weeekend I tried a 1994 ecu eprom and that didnt work at all car wouldnt idle wouldnt take the gas pedal, hesitated and, generally did NOT run worth a darn.
So now I am trying to findout where exactly in the eprom, the etc and etcs routines are located and modify them so that the eprom instructs the hardware only to look at the etc sensor for all info it needs for engine temp and fan control. Hereby eliminating the etcs routines and thus the etcs 3rd sensor will NOT be needed.

Another option would be to tie the two temp sensor output wires together at the ecu , but that will only be done if i cant find the right pipethread tap to tap the water inlet manifold so I can physically mount the 3rd sensor, because a rather do that, then cross wireing at the ecu.

Rob
 

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I don't think it got a motor swap, I think it got a climate control swap. You have an A/C button that doesn't light up, no A/C fan and no placement for the 3rd sensor. Sounds like you got a base model 6 that got upgrades to look like an LS.

I could be wrong but you shouldn't be missing two things with a button that doesn't work all relevant to the same system.
 

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Discussion Starter · #18 ·
I don't think it got a motor swap, I think it got a climate control swap. You have an A/C button that doesn't light up, no A/C fan and no placement for the 3rd sensor. Sounds like you got a base model 6 that got upgrades to look like an LS.

I could be wrong but you shouldn't be missing two things with a button that doesn't work all relevant to the same system.
Not trying to discourage your decisions for fixing the issue. Simply thinking out loud trying to figure out why the problem exists in the first place.
This is a euro car not a USA car and I am situated in europe with this car so things are a bit different.

Ok i can appriciate youre way of thinking but, the engine still has the A/C pump bracket attached to the engine. Now that can be due to 1 of 2 reasons being, that 1, the engine was swapped, or 2, that the a/c system was removed due to defekt.
Besides i dont want to have that darn fan runnin , it drives me nuts, besides it wearing out.

Thanx for takin the time to give ur opinion.

Rob
 

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Discussion Starter · #19 ·
Well anyway the problem has been solved, The waterinlet casting has been drilled and tapped and the black temp sensor been installed, and now all is well again. At least NO fan running when car is at operating temperature.

I would have like to get it to work with an eprom modification but that didnt materialize....ohh well at least the fan is quite now.

Thanx everybody for yourew info,opinion and actual help.

Rob
 
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