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Electric fan not working.....
04-03-2012, 07:55 PM
#16
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Year: 1999
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It had seemed to me you guys are saying about the same thing.
Ambient temperatures are not measured by the PCM with regards to A/c compressor operation. Low ambient temperatures will cause the fan to cycle on an off only because of the effect that cold air has on the refrigerant
And;
contacts to open. This is due to
the pressure/temperature relationship of the refrigerant
in the system.
True, temperature isn't what makes mercury rise in a thermometer, it's actually the pressure that does it.
Or maybe I'm completely missing something. Anyway I just wanted to chime in and thank Ken for helping clarify the SPDT, (Single Pole, Double Throw), relay where all the action converges. At that socket you can, *Power the fan directly, *check for power to both the fan, and the relay coil, *and check that the PCM is grounding the relay to activate the fan.
Ambient temperatures are not measured by the PCM with regards to A/c compressor operation. Low ambient temperatures will cause the fan to cycle on an off only because of the effect that cold air has on the refrigerant
And;
contacts to open. This is due to
the pressure/temperature relationship of the refrigerant
in the system.
True, temperature isn't what makes mercury rise in a thermometer, it's actually the pressure that does it.
Or maybe I'm completely missing something. Anyway I just wanted to chime in and thank Ken for helping clarify the SPDT, (Single Pole, Double Throw), relay where all the action converges. At that socket you can, *Power the fan directly, *check for power to both the fan, and the relay coil, *and check that the PCM is grounding the relay to activate the fan.
Here's the fuel pump test set up. I installed a 10 Amp fuse in place of the normal fuel pump 15 Amp fuse. This set up takes the place of the Amp draw test apparatus shown in the FSM to test for a 10 Amp (or less) Amp draw from the pump. The 10 Amp fuse didn't blow so I assume my pump is drawing less than 10 Amps. Kind of ghetto I know, but it works.
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Thawolff (02-28-2020)
04-04-2012, 07:35 PM
#17
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Djb, my main thought was its pretty handy to be able to check so much at the relay socket.
Ken, Cool. I live off grid. Got ammeters everywhere. Ghetto? You wanna talk ghetto? How about, hold the kill switch for your Onan down to run the fuel pump to prime it, (and kill it), so on start she kicks right in? Using only the original control wiring, from all, (four), switch locations. These fit OK in the control box.
Ken, Cool. I live off grid. Got ammeters everywhere. Ghetto? You wanna talk ghetto? How about, hold the kill switch for your Onan down to run the fuel pump to prime it, (and kill it), so on start she kicks right in? Using only the original control wiring, from all, (four), switch locations. These fit OK in the control box.
04-04-2012, 08:01 PM
#18
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Year: 1999
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Djb, my main thought was its pretty handy to be able to check so much at the relay socket.
Ken, Cool. I live off grid. Got ammeters everywhere. Ghetto? You wanna talk ghetto? How about, hold the kill switch for your Onan down to run the fuel pump to prime it, (and kill it), so on start she kicks right in? Using only the original control wiring, from all, (four), switch locations. These fit OK in the control box.
Ken, Cool. I live off grid. Got ammeters everywhere. Ghetto? You wanna talk ghetto? How about, hold the kill switch for your Onan down to run the fuel pump to prime it, (and kill it), so on start she kicks right in? Using only the original control wiring, from all, (four), switch locations. These fit OK in the control box.
I love ghetto tools. Especially ones that are well made, like the one I'm looking at in your photo.
Not too fond of Bubba tools however. That being said, I have made some Ghetto/Bubba crossover tools.
I made a neat crossover tool to install the rear output shaft seal on a transfer case. I'll try and take a photo of it.
04-04-2012, 11:56 PM
#20
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Ken; I don't know that I need anything installed in my rear output, but let's see it! Does it look like a can crusher? And thanks ^. All soldered....took tooo long.
Djb/Roc-Jeep..At the risk of just further confusing things...At the relay socket pictured in post #10. When the PCM grounds post 85, current flows through the relay coil from 86. The coil becomes an electromagnet to pull the contacts closed which connect power through from post 30 to 87 where it goes to the fan. So right there with a jumper you could test the fan and it's wires, by energizing 87. Also with a meter you could check for power at 30 & 86, (and so there fuses), and also see if 85 is being grounded by the PCM.
The middle, 87a is hot when it's off, then off when the relay is energized. I don't think it's used here.
I once had a similar fan in a Tempo give me a fit. Worked fine testing it, but would blow the fuse often. Everything was fine! I finally figured out it was drawing way too much current. (Ken's gadget above^, would have caught that). Fan turns free, blows great, just draws too much amperage.
As far as the other...it seemed to me those guys essentially agreed. Although the PCM might not specifically measure that temperature, it can infer it via the low gas pressure with the identical result. I don't know for sure.
Djb/Roc-Jeep..At the risk of just further confusing things...At the relay socket pictured in post #10. When the PCM grounds post 85, current flows through the relay coil from 86. The coil becomes an electromagnet to pull the contacts closed which connect power through from post 30 to 87 where it goes to the fan. So right there with a jumper you could test the fan and it's wires, by energizing 87. Also with a meter you could check for power at 30 & 86, (and so there fuses), and also see if 85 is being grounded by the PCM.
The middle, 87a is hot when it's off, then off when the relay is energized. I don't think it's used here.
I once had a similar fan in a Tempo give me a fit. Worked fine testing it, but would blow the fuse often. Everything was fine! I finally figured out it was drawing way too much current. (Ken's gadget above^, would have caught that). Fan turns free, blows great, just draws too much amperage.
As far as the other...it seemed to me those guys essentially agreed. Although the PCM might not specifically measure that temperature, it can infer it via the low gas pressure with the identical result. I don't know for sure.
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