Question-------------------------
Followup To
Question -
We have a 97 LHS that is having overheating problems similar to those posted by another individual in may of this year.
The water pump thermostat and radiator have been replaced. The system has been bled. The AC condensor has been blown out and cleaned.
The temperature sensors have been replaced. but the fan will shut off at 230 degrees.
The Automatic Climate control panel was damaged when we got the car. (Would this have anything at all to do with the cooling operations?)
Ou Mechanic has run out of ideas. Any ideas on your end?
Answer -
One other component that might prevent one or both fans from operating at all (but this is not relevant if both fans work at least some of the time when required) is a module located between the two fans at the lower edge of the structure. It is a radiointerference surpressor module and that has two sections, one for each fan, and it can open up and prevent the current from getting back to the battery to complete the fan circuit. So that is something else to check, if one of the fans doesn't work at all.
Hi Earl,
When the A/C is not on and the ambient temperature is moderate, does the coolant still go off scale? If not, then at least the radiator, pump and thermostat are working adequately. If then the problem only occurs when you need the radiator fans, and they do come on but that when the temp gets to a fairly high level , 230F , then the fans go off: your possibilities are that the temp sensor (although replaced) is failing at the higher temperatures (but that would presumably also cause a false reading on the instrument cluster which also takes its signal from the sensor so that doesn't seem to be a reasonable source of your problem). I assume that you are basing the overheating problem upon either overflow from the recovery container or an independent reading of the coolant temp, is that correct?
So it then comes down to whether or not the two fan relays are being properly activated by the controller and are they responding (closing their switches) and is there any loss of power to the switches, and if not then why won't the fans continue to operate as the temp rises to 230F. The controller operates the two relays by grounding dark blue/tan and the dark blue/pink wires at the the high and low speed fan relays, respectively. So one could monitor those wires and see if they continue to be grounded as the temperature rises. If they do, then the power to the relay switches need to be verified similarly (red/light green wires should have 12V on them all the time, even when the car is not running but most importantly when the engine is running and getting hot). Could the 40 amp fuse in the power distribution center that powers the fans be failing in the hot environment? Check to make sure that it isn't cracked and therefor opening as things heat up).
If the relay activations are being maintained by the controller, and the power for the fans is getting to the relays, then you have to measure that the fans are getting that voltage from the relays (check wiring) and if they are then check their grounds, or unplug the fans and jump to the battery to verify that they are both working. If they aren't getting voltage from the relays, then the relays' internal switch contacts are bad. I believe that when the high speed fan is needed, such as at 230F, then the low
speed fan shuts off, so focussing on the high speed fan,
relay and its activation circuit may be the items to verify. I may be wrong though and both fans might be expected to operate when the cooling needs are really severe? In any case the high speed fan isn't getting power when it should, or the fan is kaput.
It is not a complicated situation, but you just have to check each point in the circuit to figure out whether it is the high speed fan, the high speed relay, or the wire from the powertrain controller to the relay coil that is the source of the problem (or some less likely issue like the fuse supplying the switched power to the fan relay). Have you ever seen the high speed fan operate? or only just the low speed one?
That is how I would approach the problem. Let me know if I have misunderstood and made a false assumption. Also, I need to say that I am going by a contemporary circuit for the Chrysler Cirrus ('96), but Chrysler engineers tend to be very consistent in their circuit designs and wire colors.
I can't be sure of the pin number at the power controller for that dark blue/tan control wire for the high speed fan relay coil.
So pass this along to the mechanic and please let me know what he determines to be the cause.
Roland
You were right in that the car seems to operate normally when the ambient temperature is moderate. We are3 working with our mechanic on the electrical troubleshooting and will let you know how it works out.
This has confused a fair amount of folks.
AnswerHi Earl,
So it is a fan control problem, rather than a water circulation issue. That helps. By the way, the fan(s) may be programmed to come on at 210F when the vehichle speed is at 0 to 40 mph and to go off if the temp drops below 200F.
At higher speed, the fan(s) don't come on until 230 and stops when the temp is below 220F.
The fans are supposed to come on whenever the A/C is requested but that is an override on the temp sensor control of the fans. The fact that the Auto temp unit was defective shouldn't affect the temp sensor control of the fans.
Roland
