QuestionWOW! Roland, you've probably forgotten more about this type of car then I will ever learn. I agree with your last suggestion-that it the problem is probably related to the fan and its wiring, or relay. It seems wierd though that the fan can work fine when the a/c is turned on the 1st time, but not the second time? Is that how a broken fan acts? I would have thought that if the fan works at all, then the problem would be somewhere else. Also, my daughter now tells me that she thinks it has overheated a few times when she wasn't running the a/c. That makes me wonder about the temp sensor. Thoughts?
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Roland,
Thanks for the quick reply. I think from what you've said, that the problem probably isn't the thermostat or the temperature sensor. Getting into minor electrical checking is something I should be able to do. Since the radiator fan does comes on the first time we turn on the a/c, then I think the fan works--(when it gets the 12 volts) For some reason the fan doesn't come on when we turn the a/c off and then back on again, nor was it on the last time the temp light came on in the dash. My daughter saw the high temp light come on(in the instrument panel)and quickly pulled over. Before shutting off the engine she opend the hood & verified that the fan was NOT on/turning. Are these relays you mentioned expensive? Maybe it would be easier to just replace them if they are cheap. if they are expensive, I wonder if I can rig the fan to come on anytime the engine is on--is there a way to do that?
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Hi Roland. My daughter's 1992 Chrysler LeBaron LX convertible (3.0 V6) has started overheating occasionally. The car temp warning light comes on inside on the dash warning lights. (A couple of times the water has actually overflowed from the overflow bottle near the radiator)When this happens my daughter immediatly pulls off the road to let it cool down. I checked the radiator & the fluid is up to the cap and there is a little radiator fluid in the overflow container next to the radiator. There aren't any leaks. I had my daughter start the engine and then turn on the a/c & the radiator fan came on. And then she turned the a/c off, and the fan went off. However, when she turned the a/c back on, the fan didn't come on? I recently had a mechanic change the transmission speed sensor & I guess it's possible he knocked something loose, but I don't seen anything. Also, once in a while when my daughter turns her a/c on, it makes a terrible noise(squeel). I realize that might be a loose belt (or maybe the a/c clutch). The fact that the fan will come on when you turn the a/c on the 1st time tells me the fan motor is fine. Why the fan doesn't turn on after that(when the a/c is turned back on again) is beyond me. I replaced the radiator cap & it still overheats. I am now going to try and check the jumper wires from the fan to the temperature sensor near the thermostat, and possible change the thermostat. How do I trouble shoot the temperature sensor and the thermostat? After that, I don't know what to do. Any ideas or suggestions?
Answer -
Hi Jim,
Thanks for the kind evaluation. Unfortunately I don't have a document scanner so the xerox copy is the best I can offer.
On the control circuit, the fan relay is in the power distribution center under the hood, and is the most outboard one in the row. The way the circuit is set up, the a/c clutch will not be activated unless that fan relay is closed (becase that is what powers the clutch relay's coil) so as to power up the fan, unless of course the a/c relay itself is sticking in the closed condition (which it doesn't apparently seem to be). Given then that the if the a/c clutch is running the compressor, the fan relay has to be closed, then if you unplug the connector to the fan you ought to find a 12V reading between the two wires. If you do, and the fan doesn't run, then the fan is at fault. If you go to the fan relay and pull it, then neither the fan nor the a/c should run. Jumping a wire between pins 2 and 4 of the socket (the forward and rear most pins) should cause the fan to fire up and IF the a/c is requested then the compressor should then fire up also, otherwise not. The operational coils of the two relays are controlled by grounding one end of the coil which is done by the engine controller pin 31 (fan) and pin 34 (a/c), respectively. The a/c clutch relay is also in the power distribution center, directly next to the fan relay.
Roland
Hi Jim,
The circuit for the ac is designed to turn on the fan regardless of the temp of the coolant so unless it overheats when the ac is not in use the coolant temp sensor is probably doing its job of alerting the controller when the fan is required. If the overheating is happening when the ac is in use and the weather is warm then my attention would be to make sure the fan is running at that time, and then I would focus on the condition of the radiator tubing as it may have some occluded or diminished flow rate passageways. If the radiator is original and hasn't had much attention (flushing) then that may explain the overheating problem. You could remove the thermostat and test it in a pan of heating water to see if it opens fully at 195F. So those to my mind are the more important priorities. If the fan is not reliably being activated by either the call for the ac or by the temp reading without ac then the question is whether the fan, the relay, or the call for the relay is the problem. That can be checked via a voltmeter. Do you have the circuit diagram. If not I can xerox and postal mail it to you.
Roland
Answer -
HI Jim,
In response to your comment/question, the fan is not dependent upon a temp sensor signal when you ask for the a/c. It comes on whether the coolant is hot or cold, or should if it working per design. So it has to be the relay or the fan, unless the a/c relay is stuck closed on its own accord without the electrical supply from the fan relay. Because the compressor appears to respond to the ac request that explanation appears to be not applicable. So back to the fan or its wiring. I would wonder whether the fan might not also be flakey when you don't use the a/c, i.e. it isn't coming on reliably when the temp sensor asks it to do so? Also, the external appearance of a relay is not a reliable measure of its function; only by jumping 12V across the pins (from one side to the other) would you determine if it is closing its contacts, and while they are closed testing for continuity across the other set of pins.
Roland
Hi Jim,
No the relays are not very expensive. In fact several may have the same part number so you can switch them around (noting which was where to begin with so you can go back to status quo ante) to see if the problem seems to follow one of the relays as it moves or not. But again, the a/c compressor depends upon the fan relay being energized and putting out its current to BOTH the fan and the a/c relay's activation coil, otherwise the a/c relay will not be energized and so the a/c compressor will not fire up when you ask for it. This is a purposeful design to make sure the fan is always going to run when the compressor is activated. So this really points in the direction of a flakey fan motor or a problelm with its simple wiring (12V from the fan relay to the motor, light green wire) or the ground wire (black) from the fan plug to the engine ground at the upper rear of the engine. So check those two wires, see of you get 12V measuring the light green in comparison to the - post of the battery, and check that the black wire is firmly grounded at the engine (or the - post of the battery_ by a resistance or continuity test.
So that is my expectation based on the circuit as I read it. Let me know what you find...I might learn a trick from you!
Roland
AnswerHi Jim,
I got you comment and kind evaluation.
On the fan, it should come on regardless of the temperature or any other factor whenever you activate the ac compressor clutch. In fact the compressor will not come on unless the fan relay is activated, so that pretty much says the fan or its wires has to be faulty. So check to see whether you are getting 12v at the fan disconnect plug when the compressor is running. If so, then the fan ground wire may be bad or the motor flakey.
On the vacuum hose diagrams, I was able to find the one you need at www.autozone.com
You have to register with them and specify a vehicle and engine that you want to know about. Once you do that, go to the repair guides, emission controls, and then vacuum hose routing diagrams and there you will find it.click on the image to enlarge.
Yes the 3.0L thermostat does have an air vent valve.
Roland
I think the fact that she thinks it overheated when the a/c wasn't in use corroborates my belief that it is the fan, its wiring, that is no good. The compressor will only operate if the fan relay is working. It could be the sensor is also bad BUT this also happens when the a/c is "on" and that is a mode that doesn't involve the temp sensor at all, as I have said previously. You may just have to ride along with her or give her the voltohmmeter and show her how to use it when the fan fails on her, if you can't get it to fail in the driveway. That is all I can offer. Let us set aside this exchange until you do the troubleshooting I have suggested.
Roland
