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95 Cobra: Part 3, Fan Not Turning On

3K views 45 replies 8 participants last post by  Hipogt 
#1 ·
Finally took the cover off the other day and charged the battery. Since the last episodes, http://forums.corral.net/forums/94-95-tech/1445769-95-cobra-high-idle-hard-restart.html?highlight= and http://forums.corral.net/forums/94-...stalled-will-not-restart-help.html?highlight=, a friend suggested a new TPS connector. I picked up a new connector but have not installed it yet. I did try swapping back to the old IAC valve, and that put the idle back to the original 1300-1400rpm vs 2400-2500 when the new IAC was installed. But, at this point I'm more concerned with the fan not working, which obviously causes it to overheat after idling for 10-15 minutes. The fan does cycle through high and low speed during a KOEO test. ECT sensor is new, but the temperature according to the scanner is no higher than 170*. I'm guessing this is why the fan is not coming on? Other than swapping to an aftermarket fan set-up, where do I go from here?

Thanks,
 
#2 ·
Made some good headway today after this test:
Here's a simple test for you to do. While the engine's idling, disconnect the connector from the ECT sensor. If the electric fan turns on immediately you have a faulty sensor. If it doesn't, you have a problem with the low speed fan relay in the CCRM. I don't think it'll be the latter if the fan works when you switch on the AC.
The fan turned on as soon as I unplugged the ECT sensor. I tried this test about 8 months ago after this advise:
The fans not turning on.... on the ECT sensor coming off the heater tubes near the front of the intake... pull the wiring harness clip that plugs into the ECT sensor. I believe that should trigger the fans to turn on. If it doesn't, then possible CCRM related issues.
The fan did not turn on then, but that was my screw-up... I performed the test with the KOEO instead of ER.

Another milestone was the idle. With the IAC and TPS plugged in, it idled down to about 750rpm! As soon as I reconnected the ECT sensor, the fan stopped and the idle went back up to 1500rpm.

So does this point to a faulty sensor or would the connector/harness cause the same conditions? Bear in mind, the sensor is new and it did not fix the fan issue.

Opinions?
 
#3 ·
Never assume new is good. The fan is not going to come on until about 210*. The idle increasing would be normal if the ECT sensor signal indicated the car's in the warm up phase based on coolant temps.
 
#5 ·
Well, I'd like to think it is good until proven otherwise. I understand about the fan not turning on until 2xx*, I just don't understand why this sensor made no difference over the old sensor. Although I did not perform this test with the old sensor.

Are you talking about when I plugged the connector back in? That doesn't make any sense to me either, as the car was well up to operating temperature. I can understand why the fan might not be coming on, due to the "signal" that the fan(relay?) is "seeing", is only 170*, according to the live reading on the Snap-On scanner. Multiple times this senario was repeated, where the gauge on the dash is pinned on hot(overheating) and the coolant is boiling out of the bottle. All the while the scanner temperatue does not "read" over 170*, and the idle never dropped below 1300rpm with the IAC pungged in.

I don't mind replacing the sensor if this is concrete evidence that it is the only issue in the equation. I also don't want to waste money on another sensor to produce the same results.

What about the T-stat (bad, wrong temp, installed wrong, etc?), or the connector and/or harness (wire, ground?).

Thanks for the reply,
 
#4 ·
Does the car have a chip installed in the back of the processor? Are you using Ford Motorcraft parts, not super critical but Ford Motorcraft sensors work better, and last longer.
 
#6 ·
No chip installed, as far as I can tell. Looks like the processor has never been unbolted. NOT using FM parts. I believe I got it from Napa, but not sure of the brand.

Thanks,
 
#7 ·
T-stat spring faces engine. They are known to be bad out of the box. Where is the scanner connected that it's reading live data? ETC signal to the ECU is common for a whole range of operating parameters. Have you tested the TPS signal from closed throttle to WOT? Should start at about 1v and increase smoothly to +4.7v WOT. A search should be able to locate the ECT volts vs. temp curve to verify readings. Confirm or replace the rad cap. It must hold to 16 psi before releasing coolant to the overflow.
 
#8 ·
Where is the scanner connected that it's reading live data?
?? The data port connection under the hood?

Have you tested the TPS signal from closed throttle to WOT? Should start at about 1v and increase smoothly to +4.7v WOT.
Are you saying this is related to the fan issue or high idle?
It was reading over 1v closed, during one test, so I replaced it. Didn't make a difference in the idle.

A search should be able to locate the ECT volts vs. temp curve to verify readings.
I need to check into that. The car still has a lot of issues, but I'm getting tired of throwing parts at it with no results. I feel like I'm getting close, just need to narrow the issues down one by one. Right now, I'd really like to resolve this fan issue before going back to the high idle problem.

Thanks for the advise,
 
#9 · (Edited)
Okay, let's take this one step at a time.
1) You have (2) ECT sensors. (1) is located in the heater tube, it has 2 wires coming out of the connector, and goes back to the processor. I'm assuming this is the one you replaced?

2) The other ECT sensor is located in the lower intake, has 1 wire coming out of the connector, and goes to your gauge in your cluster. This is not the sensor you need to worry about.

3) Fan never turns on because processor never sees coolant temps higher than 170 degrees F. and engine overheats.
Possible causes:
3A) High resistance on the connector. Clean, and close up the female terminals.
3B) Coolant is not reaching sensor, air in system.
3C) Thermostat installed incorrectly or defective.
3D) Defective ECT sensor
3E) Incorrect range for ECT sensor

I'm assuming, the ECT sensor is still installed in the stock location.
 
#10 ·
3B) Coolant is not reaching sensor, air in system.

I was going to suggest air in the system, or crud / blockage in that heater pipe preventing the ECT from getting an accurate reading.

I lost the engine in my Explorer because of air in the coolant system, the gauge never read hot, it stayed right in the normal range. While driving I lost all my coolant, and the next thing I heard was detonation.
 
#13 ·
Removed the t-stat housing today to reveal...



NOTHING!

So , how much does this impact the reading to the fan ECT?

I'll soon find out after I install the new oem stat.

Is the WP supposed to turn CCW?

Thanks,
 
#14 ·
Have you tested it in a pot of water to check the opening temperature? WP rotation is clockwise.
 
#15 ·
Not too surprised, the new t-stat did not fix the fan issue. But at least I can cross that off the list of possible causes.



The ECT sensor? No.

Hmm, maybe I'm wrong, could swear the pump is turning counter clockwise. Rotation is determined standing in front of the engine, correct?

Thanks,
 
#20 ·
Did the rad cap ever get replaced. If the cap is holding to 16 psi the water temperature to boil is 260*F.
 
#21 ·
You know, the ECT sensor shares a circuit with ACT, TPS, EVP, & BAP sensors.

IF one of those is bad, it could also cause a problem with the rest of the circuit.
OR part of the circuit itself is bad.

I know you also have other problems, possibly they are all related.

Are you able to pull codes?
Have you checked the other sensors with a multi-meter?
Have you checked the sensor connectors for proper voltage / grounds?

just something to consider.
 
#24 ·
You know, the ECT sensor shares a circuit with ACT, TPS, EVP, & BAP sensors.
No, but thanks for opening another cans of worms for me. :rolleyes:

Are you able to pull codes?
Yes, but not recently. This is from my 9/13 post:

Anyway, here's what we got.

121 - Closed Throttle Position out of range
334 - EGR Voltage (EVP) above closed limit
543 - Fuel pump circuit open-Battery to Electronic Control Assembly (ECA)

CM Codes
113 - Intake Air Temperature signal high-circuit open
334 - See above
542 - Fuel pump circuit open-Electronic Control Assembly (ECA) to ground
543 - See above

Other things we found out:
1) Fan does not turn on, no matter how hot it gets. (It overheated at idle) ECT sensor?
2) Fans DO turn on during "test".
3) Tried the IAC from my sons' 94. Did not help.
4) Tried to swap the TPS, but it would not fit. He has a BBK TB, does that use a Fox TSP?
5) WILL NOT IDLE with IAC unplugged, no matter how much we adjust the throttle stop screw. THIS, I don't understand!?!
6) Rechecked the timing, it's dead on 10*.

Have you checked the other sensors with a multi-meter?
Only the TPS. It appeared to be out of range during one test, so it was replaced. Also replaced the IAT sensor and the IAC valve.

Have you checked the sensor connectors for proper voltage / grounds?
Yes

Thank you for the response and ideas,
 
#27 · (Edited)
1) Fan does not turn on, no matter how hot it gets. (It overheated at idle) ECT sensor?
A) I thought you tried a new ECT sensor? I'm now thinking wiring issue with the ECT circuit. Your going to need a proper wiring diagram, and a breakout box would be ideal.

2) Fans DO turn on during "test".
A) Fan 1 & 2 work from the diagnostics portion, so the fans work. Which leads me back to the ECT circuitry.

3) WILL NOT IDLE with IAC unplugged, no matter how much we adjust the throttle stop screw. THIS, I don't understand!?!
A) Related to your other issues.
 
#28 · (Edited)
Call me at 617-347-3146 I finally figured out what your problem is. Big thanks to HYBRED for giving us the tip. No laptop today and I'm not writing this stuff from my phone. Call me if you want the cure at 617-347-3147.

Thanks
Michael Plummer
 
#29 · (Edited)
* TPS, EGR, IAT, and ECT share a common signal return circuit (ground).......thanks HYBRED for pointing that out. One major thing I would like to pointout. The OBDI software is not very smart when it comes to detecting problems. Just because you get a TPS code doesn't mean the TPS is bad. The diagnostics is basically pointing out there is an issue with the circuit. Unless of course you have a hard fault.

* The processor controls this circuit pin 46 (Grey wire with red stripe). If the processor is unable to ground pin 46, you have either a bad processor, an open, or a bad connection.

* I suggest you start at the processor (pin 46) and check continuity with a digit volt meter or whatever test equipment you may have. This signals runs thru a few connectors so make sure the pins inside these connectors are tight, and not damaged.

* This is where a wiring diagram, and a breakout box would be very helpful. You may need some assistance (extra set of hands), as you follow pin 46 from the processor thru the connectors, and to it's termination point.

* If continuity is fine, then you have a bad processor. You can verify this by opening up the processor and check pins 20, 40 and 60. If damaged, you'll see the pins as it comes into the processor, and takes a 90 degree bend, they'll be burnt. How does this happen? Did you relocate your battery to your trunk? If yes, then it's not wired correctly.

* Codes 542 and 543 do not affect how the car runs or drive. If you have a remanufactured processor there is something done inside the processor that generates this code. No worries, just ignore it or get a new or used processor. Just make sure it's not remanufactured.
 
#30 ·
You can add the IAT to that shared circuit from pin 46 as well.

The TPS and EGR sensors use a shared reference voltage circuit from pin 26.
 
#31 ·
Michael, toyman, and HYBRED, thank you. I just got back from the Ford Nats at Carlisle. I had a vendor space at the swap meet and between work and packing my truck with parts, I didn't have any time last week to respond.

Depending on the weather, I may try to get back into this tomorrow.

I appreciate everyone taking the time to reply with this helpful information...

:salute:
 
#33 ·
Still haven't checked pin 46 at the PMC due to time/help issues. I did check the ECT sensor again, as I wasn't confident with my previous test results. The voltage reading with key on to the green striped was 4.7v. With the engine running hot (before boiling over), the voltage never dropped below 3.5v. At 160* the voltage value should be around 1v, 195* should read approximately .6v. Checking the ohm resistance accross the sensor, I get 2.07k, which corresponds to 212*. Tried another new ECT sensor and got the same results.

So, does the condemn the PCM, or could this still be a circuit issue?

Thanks,
 
#34 ·
As these guys stated above, all of the sensors share the same 5V reference signal, with different returns. You either have a computer issue or wiring in between. Follow Michael's instructions and you'll figure it out. You are so close! But the sensor itself is not the issue. You can be sure of that.
 
#35 ·
Thanks for the support, but I gave up today and took it to a local shop. And yes, I'm pretty aggravated with myself, as I did feel I was getting close to a solution. This latest bit of diag work was a little beyond my scope that I could handle on my own.

Hopefully they will find something soon. I'll post the results as soon as they get back to me.

Oh, BTW, stop posting pics of your Cobra,...:rolleyes: Makes me long for my '96.

Absolutely beautiful, that white '95...
 
#40 ·
Issues resolved, but problem not found... ?

It's nice to be able drive to the car without it overheating and a crazy high idle.

The problem was the common ground circuit that leads to pin 46 on the PCM. It is also the same ground circuit that goes to the data port connector. He created a known good ground using that wire. That simple task cured all three problems, even the hard to restart when warm. Honestly, I can't believe how well it runs and drives. Now, in my mind, a problem still exists somewhere in that circuit, as he created a secondary circuit, instead of repairing the original circuit. Does that make sense, or am I just over thinking this? :confused:

Hopefully this experience will help others with similar problems. All I can say to everyone seeking tech help is this. When this group that helped me gives advise,...LISTEN! Especially when they are talking about GROUND ISSUES.

The next hurdle will be getting it through inpection without the smog pump working. But that's a question for another thread. Don't want to open another can of worms here and now.

Another big thanks to Everyone that responded, especially Michael Plummer. You went above and beyond with your phone number offer, I do appreciate all the advice... :salute:
 
#42 ·
Now, in my mind, a problem still exists somewhere in that circuit, as he created a secondary circuit, instead of repairing the original circuit. Does that make sense, or am I just over thinking this? :confused:

:salute:
No actually your not overthinking, there still is a problem somewhere. If its a ground circuit its usually an accepted repair to make a secondary circuit, taboo for a power circuit. If your problem is due to corrosion inside the harness bundle, you can bet that a gremlin will come back to bite you, but if the problem is inside one wire (sheath) or at the end of the connector, your gold.
No need to go further now, just keep it in mind in case.

Enjoy your ride!!!
 
#43 ·
I am experiencing the same issues I really think I have same problem. Car is hard to start also when it was warm. Fan no functioning properly also. The 46 that comes off the PCM he just reground it. Do you have any pictures?
 
#44 ·
If you have ruled out the ECT sensor through testing, the easiest way to check that circuit is to run a jumper wire from the data port connector common ground to a known good ground.

If you need, I may be able to take some pics tomorrow.

GL,
 
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