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Followup To
Question -
ROLAND THANK YOU FOR THE PROMPT REPLY TO QUESTION I.D. 3913054 ABOUT THE COOLING FAN. I DID AS YOU DIRECTED WITH THE IGNITION TO GET THE CODES. THE ONLY CODE I GOT FROM IT WAS THE " END OF READ OUT " 55 WAS THE ONLY SEQUENCE THAT FLASHED. I REPEATED THIS THREE TIMES TO BE SURE. I ENEN STARTED THE CAR, LET IT RUN A MINUTE, SHUT IT OFF,STARTED THE SEQUENCE AGAIN STILL ONLY GETTING THE END OF CODE READ OUT OF 55. IS THERE SOMETHING ELSE TO TRY OR DID I DO IT INCORRECTLY? I'LL WATCH FOR YOU REPLY THANKS AGAIN! BILL----------------------
Followup To
Question -
coolling fan runs even before car reaches operating temp.notice gas milge has dropped some, ideles ruff on rare occation. in severe cold noticed cabin temp would drop some occationally. fan rarely shuts off.was told it could be temp sensor or fan relay? 1996 chrysler concorde lxi 3.5 litre 94,000 miles.air cond might need recharged no engine repairs except awater pump since i bought it at 62,000 miles. what needs replaced relay or sensor, and how involved to do? can a do-it-yourselfer attenpt this?
Answer -
Hi Bill,
I agree that it is either the coolant temp sensor or the fan relay which responds to the engine controller when the coolant temp sensor says the temp of the engine is high enough to warrant the aid of the fan. Fortunately there is an on-board system that can detect such failures and record which one(s) it has detected in the memory as a two-digit fault code. All you have to do is readout the controller memory using your ignition key.
Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). Then watch the 'check engine' light to come "on" and then begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the two digits of each number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout". The code for the coolant temp sensor being faulty is 22, while the one for the relay of the fan is 35. I can help you with the repair once we have the readout.
If the fan came on too early, that would cause the engine to run too cool as your described.
Roland
Answer -
P.S. The fact that no codes came up just means that there is not a major electical problem with the temp sensor or the fan relays. But it could very well be that the temp sensor is off-value (misreading the temp of the coolant and saying "I'm hot" when it really isn't). The fact that the fan comes on and off suggests that the relay(s) at least are working and presumably 'under the control' of the engine controller even though possibly misinformed.
If you don't have an ohmmeter, but you can find the sensor and can remove the plug (lift the tab) and can get a proper size box wrench on its hexagonal flats, then you might try loosening it a bit to make sure it is removable. Then if you want to take a chance, go get a replacement sensor for the specific year and engine and put it in place of the old one. Wrap the threads with a couple of layers of teflon plumbing tape to seal it and lubricate the threads if you have to remove it in the future. The water in the system may buble out of the hole when you remove the old one, so be ready to insert the new one a.s.a.p. It is probably not that big an investment, thought if you don't have a volt-ohmmeter that would be worth getting if you contiue in the do-it-yourself mode. I can't guarantee the sensor is bad (only a measurement would prove it) but it is suspicious that the fan works now the way it does.
Roland
Hi Bill,
The next step is to measure the resistance of the engine coolant temp sensor and the temperature of the coolant to see if either the sensor is off value or the thermostat is stuck in the open or closed position. Do you have an ohmmeter? and how about a meat thermometer or similar thermometer.
The resistance across the terminals of the temp sensor changes as the engine warms up. But to test it we need to have those two test equipment items. So let me know about that. The temp sensor is located adjacent to the thermostat housing on the top front of the engine (the housing has a fat radiator hose coming out of it). the sensor is next to that housing and is a cylindrical-shaped device with an electrical plug in the top of it and the other end is screwed into the block. The two wires are black/light blue and tan/black. Let me know if you can locate it.
The plug with the wires has a tab that you lift in order to release the plug from the sensor. You will place the ohmmeter across the two pins in the top of the sensor and set the meter to read in the range of several thousand ohms. When the engine is cold it should read around 10,000 to 13,000 ohms. Put the plug back in and then you start and run the engine the for a while until the temp gauge on the dash reads upscale to the point where it usually sits; stop the engine and disconnect the plug again and re-read the resistance in ohms. Depending upon how hot the engine is it should have dropped to a resistance of 700 to 1,000 ohms. Before you do all of this put the thermometer on the block so that its shaft is in contact with the metal and is close to the temp sensor. Let it sit there for a while until it has stabilized and see what it reads in Fahrenheit after you have warmed up the engine. Then get back to me with the result. Also, note during the warm-up as to when the fan came on and what the temp gauge on the dash read when it did, and also pull the electrical plug (after shutting off the engine) and read the resistance of the sensor at that time. Then reconnect the sensor plug and let the engine warm up fully even though the fan is still running and the do the resistance and the thermometer reading as I described above.
Then get back to me with the results and we'll decide what it means and what to do next.
As for the relays, there are two fan relays, one for low and one for high speed and they are located in the power distribution center located in the engine compartment on the drivers side, next to the power brake unit. Open the lid on the box and you will see a key that shows the two fan relays. Notice whether the fan relays have the same part number as any other relay or not. If it does try trading out the relays so as to get different relays in the sockets (but keep track of how you traded them around). If the fan relays are unique, then switch them only. Then see if doing that changed the behavior of the fan when the engine has cooled down: restart it and observe if it is still coming on pretty quickly or not as before.
This is the sort of testing and data that will get to the bottom of the problem,
Roland
HI ROLAND,
I'M STILL WOKING ON THE COOLING FAN PROBLEM. SINCE YOUR LAST RESPONSE I REPLACED THE COOLANT SENSOR SWITCH. THE FANS STILL RAN. I TRIED CHANGING AROUND THE RELAYS, FOUR OF THEM WERE THE SAME NUMBER. I DID THIS WITH THE CAR RUNNING AND THE TEMP WAS BELOW NORMAL, SO THE FAN SHOULD HAVE SHUT OFF WHEN I SWTCHED THE RELAY. IT DID NOT, THE ONLY TIME THE FAN STOPPED WAS WHEN THERE WAS NO RELAY IN THE SOCKET. WHILE DOING THIS, I NOW HAVE A "CHECK ENGINE" LIGHT ON IN THE DASHBOARD. I GOT THE CODE THAT FLASHES NOW AFTER DOING THIS. IT NOW HAS A READ OUT OF 12 35 55. WHAT IS THE NEXT STEP?
BILL
AnswerHi Bill,
If you verify the coolant sensor wires are connected all the way to the controller. Then as I said you need to look at the fan relay socket(s) to find the wire(s) that go from there to the engine controller.
The dark blue/pink wire that when grounded activates the fan relay goes from pin 31 of the 60-way to one of the pins on the relay. So when you pull the 60-way, see which one of the cavities on the relay socket is connected to pin 31, using your ohmmeter. Then reconnect the 60-way and see if that same relay cavity is grounded, both when the engine is not running and when the engine is running. It should not be grounded (0 ohms between it and the - post of the battery) except when the engine is running quite hot so as to call for the fans to come on. If it is grounded, then remove the 60 way and see if it is still grounded: if it is then the wire is shorted to ground somewhere between the 60-way and the relay socket. Try shaking the wires between the power distribution center and the controller to see if you can "clear" the ground, and if so that is the area of the short to ground. If it is not grounded, then the controller socket for pin 31 has to be grounded and is falsely calling for the fans when it shouldn't be, and that pretty much means you need a new controller.
Hi Bill,
That is good follow up. The code 35 was set when you tried to run the engine without the fan relay in the socket. I assume that the coolant sensor was verified to be designed for your specific engine and year (if not verified, do that first). The only other possibility I can think of is that one or both of the wires between the coolant sensor and the engine control unit (mounted on the right fender shield) are not making the connection due to a loose connector, broken wire or bent pin at the controller. So look carefully at the wires to the sensor, and follow them if possible to a multi pin connector and check that by opening it and looking for problems with the pins or sockets. Then I would go to the engine controller and remove the 60-way plug there. Then you will need to have an ohmmeter in order to verify that the connector at the sensor plug is actually connected to the controller pins. If you hold plug with the pins facing you and the short tab up, the #1 pin is the one on the left end/top row. The tan/black wire at the sensor connector should be attached to the #2 pin, and the black/light blue wire should be connected to pin #4. If it passed that test, and the sensor is the correct one, then the last possibility is that the wire that goes from the controller to the fan relay socket is shorted to ground (which is what the controller is supposed to do to turn the fan on, otherwise it should "float"). That wire is dark blue/pink and the socket might be number 5 if it is labelled or the pins on the relay are labelled. What you could do is disconnect the battery and then see if any of the pins of the relay socket are grounded (reads 0 ohms resistance when bridged to the engine block) and if one of them did then I would trace that wire and find out where it's insulation has broken and is thus grounding the control wire which causes the fan relay to activate the fan.
Roland
The 35 code will go away in a while, or when you disconnect the battery it will also be gone when you reconnect the battery when the relay is back in the socket.
