So today, when I turned the ignition switch to ON (without starting the car), I noticed a "sound" coming from the engine bay. It was a low pitch sound, much like the radiator fan (but much quieter). This was with an engine at temperature (I had driven the car for some 30 minutes and then parked the car for about 10 minutes). I can't remember ever hearing this sound before (and I've had this car for 26 years now).
So what is that? Is that the oil pump? And should it be running even without the engine running?
So today, when I turned the ignition switch to ON (without starting the car), I noticed a "sound" coming from the engine bay. It was a low pitch sound, much like the radiator fan (but much quieter). This was with an engine at temperature (I had driven the car for some 30 minutes and then parked the car for about 10 minutes). I can't remember ever hearing this sound before (and I've had this car for 26 years now).
So what is that? Is that the oil pump? And should it be running even without the engine running?
The ONLY thing that should be coming on when you first turn the car to the "ON" position, without starting it... is the fuel pump. It's "priming the line" by pressurizing it just before you attempt to start the car. If everything is working well, it SHOULD run for about ~10 seconds and then shut off (unless you start the car, in which case it will continue).
Note, the oil pump is mechanical, and it will only run when the engine is running, because it's fed off either the crank of the cam... but I honestly cannot remember. You would never hear that because it would be practically impossible to separate that sound from the engine itself.
The ONLY thing that should be coming on when you first turn the car to the "ON" position, without starting it... is the fuel pump. It's "priming the line" by pressurizing it just before you attempt to start the car. If everything is working well, it SHOULD run for about ~10 seconds and then shut off (unless you start the car, in which case it will continue).
Ok, so apparently, this is the trunk fan (it's coming from the right side of the engine compartment).
The reason I've probably never heard it before is because it should never run alone and only at the same time as the radiator fan. But the radiator fan is not running. So something is not right here.
So today, when I turned the ignition switch to ON (without starting the car), I noticed a "sound" coming from the engine bay. It was a low pitch sound...
I thought it might've been the sound of your poor suffering Fiero moaning and pleading to have its oil filter changed!
I thought it might've been the sound of your poor suffering Fiero moaning and pleading to have its oil filter changed!
There are soooo many "small" maintenance things to do on this car which I would have done long time ago if I had my own garage. Mind you, I have to do everything at the side of the road and this being the Netherlands, we have about 1 month per year that it doesn't rain or isn't freezing cold... The past year, that time was spent on replacing the radiator, heater core and exhaust. The heater core was the last thing I did. A few days later it started raining and it hasn't stopped raining since.
My Fiero is leaking fluid from everywhere - transmission oil, engine oil and coolant. But I have to wait until at least May for the weather to clear up (and temperatures to rise) long enough to work on the car.
But I have to wait until at least May for the weather to clear up (and temperatures to rise) long enough to work on the car.
Now granted, I did this in a friends yard (and not on the street)... but when I swapped in a 5-spd and replaced the clutch in my '84 Fiero in Decembrrr of 2009, I went to rinse my hands off in a bucket of soapy water we had nearby for that purpose... and I discovered it was frozen solid.
Originally posted by Cliff Pennock: The reason I've probably never heard it before is because it should never run alone and only at the same time as the radiator fan. But the radiator fan is not running. So something is not right here.
You're coolant issues are wearing me slick. Is your radiator fan coming on?
It feels like I fix on issue, and another one pops up.
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Is your radiator fan coming on?
It has sometimes. Since I replaced the radiator, it hasn't come on as often as it used to. In fact, it hasn't come on since (outside) temperatures dropped drastically to around 40*F. And looking at engine temps, it isn't surprising at all the fan doesn't come on. The gauge says temps are between 175*F - 195*F. So I'm not sure why the engine bay fan *does* come on.
It has sometimes. Since I replaced the radiator, it hasn't come on as often as it used to. In fact, it hasn't come on since (outside) temperatures dropped drastically to around 40*F. And looking at engine temps, it isn't surprising at all the fan doesn't come on. The gauge says temps are between 175*F - 195*F. So I'm not sure why the engine bay fan *does* come on.
Does your car have A/C? The fans - both of them - are supposed to come on whenever the A/C is energized, except when it's in "defrost". Can't imagine why one would run without the other, though.
If your car does not have A/C, then the fans (AFAIK) are only controlled by the sender, near the thermostat.
[This message has been edited by Raydar (edited 12-01-2023).]
The fans - both of them - are supposed to come on whenever the A/C is energized, except when it's in "defrost".
Really? I didn't know that. I thought the rad fan and trunk blower were always synced to come on together, no matter whether it was the fan switch (on the engine) or HVAC/defrost that triggered them. Learn something new every day!
[This message has been edited by Patrick (edited 12-01-2023).]
Ok, so apparently, this is the trunk fan (it's coming from the right side of the engine compartment).
The reason I've probably never heard it before is because it should never run alone and only at the same time as the radiator fan. But the radiator fan is not running. So something is not right here.
It isn't on always. Only when the engine is at operating temperature. But like I said, at operating temperature, temperatures aren't high enough for the radiator fan to come on. Yet the engine bay fan does come on. I have no idea what triggers it.
Why is the coolant fan relay different from the engine blower relay?
It looks like there's an extra resistor parallel to the relay. Why?
Show me the whole page please.
And this is starting to nudge my memory. The trunk fan is supposed to keep the coil/distributor and (I think) alternator cool. That has nothing to do with your engine coolant temperature.
Funny side story. A lot of those were wired backwards, so the fan sucked instead of blowing.
Originally posted by Cliff Pennock: Why is the coolant fan relay different from the engine blower relay?
It looks like there's an extra resistor parallel to the relay. Why?
Is very likely diagram is wrong w/ resistor. Most, not all, car relays have a Diode on the coil as "surge protection" when coil is turn Off.
Many diagrams don't have the Diode but actual parts do have them. Some maybe hidden in the coil. Sometimes you can test them w/ Ω meter w/ coil resistance changes for which way the probe are used.
Maybe correct using a resistor instead for same reason. Gen2 HL module has resistors across motor control pins for this reason but unlike diode, in this case power gets reverse & need something that won't notice.
Physically the relays are way different & no work. If blower relay is bad & can't get now, just get same relay & pigtail plug as F-pump. The "standard" relay used by many things I think handles 20A @ "12v" DC.
Originally posted by buddycraigg: Show me the whole page please.
left is single speed rad fan in many "books" including FSM & Alldata. right is I think engine blower but both on same page in whatever "book." Alldata & some others show as separate diagrams.
It is probably a diode in the relay and not a resistor. A diode in this kind of circuit would keep it from back feeding when the magnetic field collapses when the relay is turned off. A resister would give a "controlled" short circuit for something like a rotating motor coming to a stop.
I would still like to see the whole page of the schematic.
[This message has been edited by buddycraigg (edited 12-13-2023).]
That was posted by fierosound. I thought this came from the service manual, but I can't find that page in mine. Well, not in the digital version. I'll have to look for my own service manual and see if I can find the page there
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That has nothing to do with your engine coolant temperature.
No, but they are controlled by the same sensor. So one shouldn't run without the other.
The above diagram was posted by fierosound and it apparently came from a different version of the service manual than I have since I can't find that page in mine. However, in my service manual, I see similar depictions of the fan relay - all showing a resistor instead of a diode.
That said, a diode makes sense, a resistor doesn't. But I can't see why they would have the same error across different versions of the service manual...
"Authors"/"editors" of FSM copy/past as much data as possible even from other model lines & often doesn't check the data is True. Example: The entire 84-86 FSM rear brake sections for Fiero has huge problems not corrected even in TSB until rework that section for 87 Fiero FSM
Many errors "upstream" cause by drafters etc that don't look very hard @ wire diagrams & other "pictures"/drawings they output to nearly everyone else.
Alldata unlike most others have exact same data & errors in GM & other FSM because paid a huge fee for Licensing. IOW alldata shows same resistor there for 86 & likely other years.
I don't have a spare rad fan relay handy to take apart to check how it made. Pain in the ass to look @ one in the car.
Side note: Many Trust P22 & related parts books to get GM PN but they have problems too & why all "books" list wrong rad cap until someone got lucky to get Stant to correct that number to non-vent cap. Other "books" including Motorad still list the vented cap to match wrong number in P22.
Engine blower relay & motor runs off E-fan fuse. (E-fan to Brn wire to 2 pins on relay) Rad fan... the coil is wire to E-fan fuse but gets Power directly from Fuse Link A 24/7 & Both can Turn On w/o warning like turn i-key to run & have AC/Heat control head set to AC. In fact... make sure the control head is Off, Vent or Heat settings. (Defog runs AC to when weather is warm enough & may try to run the rad fad & engine blower even tho "books" say doesn't run them.) Why? Is possible this is set to AC, engine blower is On as normal but have wiring or other problems to the Rad Fan & Fails to turn On.
Both should be On @ same time but if one Fails the other can be On or Off depending exact problem. Also AC high limit can run them too in V6. Not just coolant temp or ac control head.
Bottom line here is the radiator fan and rear coil and alternator air blower comes on at the same time. The reason for this is the old alternator design with the disc fan. The 88V6 models had the steel fan design on the alternator. It was strange that ignition coil didn’t need the blower tube on the 88GT and Formula, probably because GM did testing that it wasn’t necessary. But the 88V6 had a rear manifold shield to deal with heat. The 85-87V6 had a different shield (on original cars) on the alternator. I would recommend that the 88V6 manifold shield be used because less heat, is better, even though some will say they never had an alternator failure without this 88V6 specific shield.
It was strange that ignition coil didn’t need the blower tube on the 88GT and Formula...
I believe that was because the exhaust Y-pipe on the '88 2.8 was vastly superior to the '85-'87 design in regards to how well it kept heat away from the ignition coil and ICM.
Patrick, that is true. The 88V6 had the improve / added heat shielding on all the “Y” pipe and up to the manifolds. That indeed was a better setup. I always preferred / liked that heat shielding because it looks more exotic than just tin shields that could bend and could cause vibration if it would touch something. That 88 type shielding is still used today.
I didn't know that. I thought the rad fan and trunk blower were always synced to come on together, no matter whether it was the fan switch (on the engine) or HVAC/defrost that triggered them. Learn something new every day!
