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Apr 27, 2024 11:13
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- HandlingByJebus
- Jun 21, 2009
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All of a sudden, I found myself in love with the world, so there was only one thing I could do:
was ding a ding dang, my dang a long racecar.
It's a love affair. Mainly jebus, and my racecar.
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mmmmm, no there wasn't. It has 2 supplemental electric fans that are meant to only kick on with the AC, but will also kick on when the engine is above 95C; he was talking about running just those (once he gets the second one working again).
Those fans alone wouldn't be enough to do much more than just tool around town, but add a big (or two medium) puller fans on the other side and it just may be enough. The problem you'd run into at that point is if the alternator can keep up.
Yeah - the 16” SPAL units draw 25A. I would probably set them up so that one came on at ~80 degrees C and the other came on at ~95 degrees C if running a pair. I’m going to use a solid-state relay (32A peak / 20A continuous) to PWM the fuel pump on the Zed, was considering running a pair in parallel to do the same for the fan. I bet there are smart fan controllers that would allow similar functionality in this application without a standalone ECU though 
Fake edit: looks like that alternator is either 150A or 180A, so that should be plenty beefy to run 50A of fans.
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Jun 8, 2019 04:15
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- HandlingByJebus
- Jun 21, 2009
-
All of a sudden, I found myself in love with the world, so there was only one thing I could do:
was ding a ding dang, my dang a long racecar.
It's a love affair. Mainly jebus, and my racecar.
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Mercedeeeeeees...!
Okay, so it appears my TPS isn't really a potentiometer, it's a switch. Somehow. And to check it, you're supposed to measure resistance, not voltage. I'm decent enough with electrical and electronic stuff in general, but once you put either of those in a car, I get confused and anxious.
Problem: My manual doesn't say much at all about what values to look for when measuring said resistance, only that it's supposed to end up at zero Ohm's when throttle is fully engaged. Also, the switch itself is located at the throttle body, which is underneath the air flow sensor, which is underneath the fuel distributor octopus. That means I have to measure at the terminator. That, in turn, might be one out of two possible plugs. One looks right, but has four wires coming out of it, not three. The other's got one, not three. There are supposed to be three wires. So I'm at a loss.
Didn't get much further than that this weekend, and am seriously considering letting a trained professional handle this particular problem.
Good news though, I found out that my aux fans work! Both of them, even the one that was jammed stuck with corrosion, spin up with much gusto and excitement when fed 12 V directly. I'm positive that with both those babies running, I'll have exactly zero need for the big mechanical fan. Bad news is that they're supposed to spin up at a low setting above a certain coolant temperature, and at full blast at some higher temperature, but even after having run the engine up to 110 Celsius, I still haven't seen a hint of that low setting. So either there's a busted sensor somewhere, or there's a busted relay... so that's another thing I might want to hand over to a workshop.
Of course, a friend who came over and helped out noticed a vacuum line hanging loose, outside a connector. I have no idea what it's for, but for all I know, those power issues might have been caused by that.
Edit: It's literally 90 degrees F here now; not braining so well. Re: fans, doing some further reading, it seems they're only set to come online in the slow setting when refrigerant pressure exceeds so-and-so. As I've removed half of my AC system, and unhooked the belt from the AC compressor, that's not going to happen any time soon. Going to have to see if I can bypass that detection, I guess? Still kinda weird that they won't power up on the high setting, though, since they're supposed to do that anyway.
Your throttle position sensor is a variable resistor. You can test it right at the throttle body so long as you have access to the pins on the plug, which should be 3. One for ground, one for +5V ("sensor reference voltage"), one for output. If you measure between +5V and output pins, you should see 0 ohms or thereabouts at WOT, and something like 50k / 100k / 500k ohms fully closed, without weird spikes up or down as you open and close the throttle. The factory service manual should specify what the fully closed resistance is, the value is somewhat arbitrary but it is specific to the application.
Alternatively, with the ignition on you should be able to measure a voltage between ground and the output pin. That should be ~0V (it's around 0.26V on my car) with the throttle completely closed and ~5V (around 4.7V on my car) when fully open.
What the ECU does is feed a reference voltage (usually +5V) into one side (or the wiper) of the variable resistor. The wiper (knob) of the variable resistor is attached to the shaft of the throttle, so when the throttle moves, it turns the knob on the variable resistor, changing its value. One of the other pins (wiper if that's not where +5V goes, or one of the sides if it is) is connected to the throttle position sensor input, which sees a voltage between 0 and 5V that is relative to throttle position.
HTH.
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Jul 29, 2019 16:14
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Jun 3, 2019 23:07
