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Engine fan clicks on off ....
- Thread starter Ertech
- Start date
The low-speed fans are controlled by the pressure switch on the a/c reservoir. You could have low freon, or the pressure switch could be going bad, or the step-down resistor right behind the left headlight could have a bad connection. The terminals for the wires connecting to the resistor (a big spring about 3/4" in diameter) are known for corroding. The spring is usually okay but the terminals corrode and/or simply deteriorate due to the high heat.
There are two pressure switches on the reservoir. If you want to troubleshoot, pull the connectors off the black switch and jump them together (the connectors -- not the terminals of the switch itself). With the wires connected, the fans should run on low continuously. If the intermittent fan issue stops, then it's likely low freon or a bad pressure switch.
There are two pressure switches on the reservoir. If you want to troubleshoot, pull the connectors off the black switch and jump them together (the connectors -- not the terminals of the switch itself). With the wires connected, the fans should run on low continuously. If the intermittent fan issue stops, then it's likely low freon or a bad pressure switch.
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Has you upper wiring harness been replaced?
Some years ago I had some weirdness with the electric fans and/or the climate control. It was hard to explain because the issues were not 100% repeatable, but in general the electric fans sometimes turned on when I wasn’t expecting them to and sometimes did not turn on when I DID expect them to. As well, sometimes the AC compressor would not engage when I expected it to.
I eventually replaced the upper wiring harness and it has all been good ever since. IIRC some of the inputs that decide if the electric fans/AC compressor engage have to do with sensors fed by the upper harness. At least from what I remember. The job is easier and faster than you might think, and this is coming from someone who always breaks stuff. When I peeled back the insulation to my original harness, I realized it had disintegrated and was junk .... surely some conductors were shorting against each other.
That is correct. The three coolant temperature sensors in the front-side of the intake manifold are connected via the upper wiring harness.
If you rule out the receiver dryer pressure switch and the low speed fan resistor terminals as a problem, you may want to check the two ice cube relays behind the fuse box for proper operation as they control the fans too. A failing relay could cause the fan to operate intermittently.
hi guys did some digging today . here is the latest:
when I turn off the climate control even from heat I could here the relay B click on and off for a few seconds and the fans also go on high on and off.
I jumped the wires at the red pressure switch on the dryer and low fans come on
what can this be?
what would make the high fans come on and off a few times when the climate control turned off ?
when I turn off the climate control even from heat I could here the relay B click on and off for a few seconds and the fans also go on high on and off.
I jumped the wires at the red pressure switch on the dryer and low fans come on
what can this be?
what would make the high fans come on and off a few times when the climate control turned off ?
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No, they do not.
The high-speed of the electric fan only goes on when the coolant is 105-107C or higher, when the engine is running. It is only activated by coolant temperature, not by heater or A/C operation or other variables.
Also, the fans do not operate after the engine is shut off, even if the coolant temp climbs temporarily in the minutes after things are shut down (for example, in a parking lot on a hot summer day).
Also, the fans do not operate after the engine is shut off, even if the coolant temp climbs temporarily in the minutes after things are shut down (for example, in a parking lot on a hot summer day).
I wonder if this would be a worthwhile modification to effect --- i.e. turning on the electric fans for a bit after the car has been parked, until underhood temps get down to a certain level...... many modern cars, as well as many of the w124's contemporaries do this.....
I think it would be a nice modification, however I'm not sure if power is available at the relay(s) with the ignition switched off. If not, it would get complicated.
I think even Priiiii do this -- ?
Dunno. I might have opened the hood once or twice, a few years ago, to change a lightbulb. Not sure what’s under the hood of that thing. Like I said ..... near ZERO maintenance.
A while back, I asked my shop to tap into the auxiliary fans high speed and then install a switch in the space for the audio fader, which was no longer being used. I can turn the fans on and off at will and still retain the automatic trigger for low and high speeds (although the automatic high speed trigger for me is at 98C, since I have the cool harness installed). Had to use an antenna switch, as it needs to click to activate the fans. The initial idea was to use the switch for the fresh air circulation with a red light, but that one does not click to activate. But the antenna switch does light up, so I can it at night and it blends in well with rest of the illuminating windows switches and the passenger side mirror button.
I did this mod mostly for use at the track, during the cool down laps. Willow Springs raceway in Kern County, CA and the Roval track in Fontana, CA do get quite hot in Summer and early Fall, and tracking the car there can be brutal. So this helped me in keeping the coolant temperature under control. Away from the track, I have found it to be prefect when sitting in very long summer traffic, when I don’t want to wait for the 98C coolant temperature and want to activate the fans earlier on to keep the engine cooler. The fans are original and have not been abused over time. But I don’t activate the fans unless I really need to and do not run them for a long time, usually for the same amount of time the automatic on and off trigger time from the factory.
I did this mod mostly for use at the track, during the cool down laps. Willow Springs raceway in Kern County, CA and the Roval track in Fontana, CA do get quite hot in Summer and early Fall, and tracking the car there can be brutal. So this helped me in keeping the coolant temperature under control. Away from the track, I have found it to be prefect when sitting in very long summer traffic, when I don’t want to wait for the 98C coolant temperature and want to activate the fans earlier on to keep the engine cooler. The fans are original and have not been abused over time. But I don’t activate the fans unless I really need to and do not run them for a long time, usually for the same amount of time the automatic on and off trigger time from the factory.
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