Cooling fans with fan fail fix

[Evildeli]

I've had my D for over 5 years now and I just don't know what is considered normal for my fans. I've got Hervey's fan fail fix left over from PO and I plan to replace eventually with Toby fans. But until then I want to make sure everything is okay. Usually when I drive the fans will cycle on and off, but then again I've had AC problems from the start with my car. I've replaced the whole AC system and converted to r-134a and it all seems to be staying cool. My concern is that when I drove the car to Lakeland over the weekend, which took over an hour and half, the cooling fans stayed on the entire time. I've had the fan fail stick once or twice before, but when the turned the AC off, the cooling fans turned off too, so I don't believe the switch is sticking. Is the cooling fans suppose to stay on the whole time, or is it suppose to cycle?

[Ron]

The fans will come on anytime you select Max, Norm, or Bi-Level. Otherwise, the otterstat controls them -- it will cycle them on-off depending on the coolant temperature. Watch your temp gauge closely and you should see it raise and lower as the fans go off and on. If in doubt, find someone with a laser thermometer (or similar tool) and compare with the gauge.

[TTait]

So if your car warms up to normal operating temp the fans will usually come on as well.

[Bitsyncmaster]

The fans will come on anytime you select Max, Norm, or Bi-Level. Otherwise, the otterstat controls them -- it will cycle them on-off depending on the coolant temperature. Watch your temp gauge closely and you should see it raise and lower as the fans go off and on. If in doubt, find someone with a laser thermometer (or similar tool) and compare with the gauge.

Actually the fans will run when the AC compressor is running. Hence if the AC is cycling, so will the fans.

[DMC5180]

The fans will come on anytime you select Max, Norm, or Bi-Level, otherwise the otterstat controls them.

And under normal circumstances, cycle ON/OFF with the A/C clutch. Unless the the Otterstat is closed, which does not seem to be the case here. I don't think I've had the A/C not cycle off, but I don't live in a hot climate either.

[Ron]

Actually the fans will run when the AC compressor is running. Hence if the AC is cycling, so will the fans.
OOPS! That's right....the manual lies (N:08:15) and I forgot about the low pressure switch.

EDIT: Now you got me thinking...why not move the tap to the fans behind the pressure switch...this would let the fans catch up on cooling. [pondering on that a while...]


And under normal circumstances, cycle ON/OFF with the A/C clutch. Unless the the Otterstat is closed, which does not seem to be the case here. I don't think I've had the A/C not cycle off, but I don't live in a hot climate either.
Same here..partially why I oops...there was an endless debate on whether AC should ever cycle off with ("normal" hot weather and) a properly charged system. It died. RIP! lol

[DMCMW Dave]

Another good test - jump the otterstat so the fans run all the time. If they still cycle, replace the breaker.

[David T]

Depending on how the A/C was set up during the conversion the A/C may not be cycling as it should. The fans run under two conditions with the key on:
When the otterstadt switch is hot enough.
When the A/C compressor clutch is engaged (mode switch to MAX or A/C and the low pressure switch is closed).
This is assuming of course, the circuit breaker is not popping and resetting. You can hear it actually making noise if you remove the carpet and the wood cover while driving the car. The fix is to replace it with an uprated one. If the A/C is not cycling you may have to adjust the charge and adjust the low pressure switch for the higher pressures you have to run -134 at.
David Teitelbaum

[Ron]

Just in case...


And under normal circumstances, cycle ON/OFF with the A/C clutch. Unless the the Otterstat is closed, which does not seem to be the case here.
Having re-read all this, it could be, if he meant the below literally.


My concern is that when I drove the car to Lakeland over the weekend, which took over an hour and half, the cooling fans stayed on the entire time.

Internally shorted/Flaky Otterstat?

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Another good test - jump the otterstat so the fans run all the time. If they still cycle, replace the breaker.!

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Thermostat stuck in partially open position?

[Evildeli]

Actually I just replace the otterstat 3 months ago. Also, the car did not overheat when I drove her, but I'm concerned that with the fan running the whole time, I'm gonna melt my fuse box. It already needs to be redone anyways.

[Ron]

So, now, even when it is cold, the fans run all the time? If so unplug either side of the otterstat and see if it quits...before it warms up.

[Evildeli]

Fans only run when AC is turned on. Want me to turn AC on and then unplug otterstat?

[Ron]

OK...that's normal. When the engine is cool, start it up and let it run on max then wait for the compressor clutch to kick off and see if the fans kick off at the same time. The cluch might not kick off, depending on the temps and charge...

[Bitsyncmaster]

EDIT: Now you got me thinking...why not move the tap to the fans behind the pressure switch...this would let the fans catch up on cooling. [pondering on that a while...]


Same here..partially why I oops...there was an endless debate on whether AC should ever cycle off with ("normal" hot weather and) a properly charged system. It died. RIP! lol

I already fixed that with my solid state fan relay. It keeps the fans running a minimum of 20 seconds. So unless your compressor cycle time is longer than that....the fans don't turn off.

[lazabby]

... This is assuming of course, the circuit breaker is not popping and resetting. You can hear it actually making noise if you remove the carpet and the wood cover while driving the car. The fix is to replace it with an uprated one. If the A/C is not cycling you may have to adjust the charge and adjust the low pressure switch for the higher pressures you have to run -134 at.
David Teitelbaum

I have a question about this. Yesterday I was going to an event and decided to remove the carpet and cover over the fuse box. While at lights, there was a lot of "clicking" when the AC clutch was engaged/disengaged, say every three seconds or so. It wouldn't happen when I turned the AC off. After the car was thouroughly warmed up (about 15-20 minutes) the clicking stopped. Is this a bad relay?

[Ron]

I already fixed that with my solid state fan relay. It keeps the fans running a minimum of 20 seconds. So unless your compressor cycle time is longer than that....the fans don't turn off.
Well...if/when I have a problem with mine I'll purchase one ;-)

Seriously though, considering the track record of your other products, I would HIGHLY recommend it for people who live in hotter climates for that reason alone (and I rarely plug anything ;-)

[Bitsyncmaster]

I have a question about this. Yesterday I was going to an event and decided to remove the carpet and cover over the fuse box. While at lights, there was a lot of "clicking" when the AC clutch was engaged/disengaged, say every three seconds or so. It wouldn't happen when I turned the AC off. After the car was thouroughly warmed up (about 15-20 minutes) the clicking stopped. Is this a bad relay?

That is your fan relay or the relays in your fan controller if you have one.

[Ron]

Depending on how the A/C was set up during the conversion the A/C may not be cycling as it should. The fans run under two conditions with the key on:
When the otterstadt switch is hot enough.
When the A/C compressor clutch is engaged (mode switch to MAX or A/C and the low pressure switch is closed).
This is assuming of course, the circuit breaker is not popping and resetting. You can hear it actually making noise if you remove the carpet and the wood cover while driving the car. The fix is to replace it with an uprated one. If the A/C is not cycling you may have to adjust the charge and adjust the low pressure switch for the higher pressures you have to run -134 at.
David Teitelbaum+1

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And to avoid confusion:

MAX, NORM and BI-LEVEL are all A/C settings that will engage the clutch.

"Low pressure" switch is kind of a misnomer (in a D system). It will cut out any time the charge is too low to protect the system. But, when the system is in perfect condition (including charge), it will turn the compressor off when:
-The refrigerant pressure low as a result of low ambient temp.
-The ambient temp is high and cabin temp is low (the evaporator exchanges little cooling because the cabin is already cool).
-The ambient temp is warm/high and fan set on low (little exchange...)

Yet, it is not only possible, but very common (and some say ideal) for the clutch to never cycle depending on the temps and/or user settings.

[Evildeli]

I started the car from cold and after about 1 minute I turned on the AC. The fans came on at the same time. I went through Hervey's sight again and noticed this;
http://www.specialtauto.com/delorean-parts/images/ac-pressure-cycling-switch.jpg

He has 2 versions. One for r-12 and and one for r-134a. If I still have the r-12 version in there could this be the culprit?

[Ron]

I started the car from cold and after about 1 minute I turned on the AC. The fans came on at the same time. That's ok...but we need to know, if you then leave the settings and all alone, does the compressor EVER kick off and if it does, do the fans go off at the same time. If not, it can simply be the ambient temp is such that it does not 'want' to turn off the compressor because the Freon (going into the evaporator) is not near the freeze point (too cold).

I should of thought of this earlier (I'm awake lol):

Do not linger between/skip steps.
With D cold (KEY!).

Start engine and turn AC to MAX, doors shut. Compressor should run.

If fans are running, unplug low pressure switch.

If fans are NOT running, there should be no problem with the fans created by the AC.
If fans are running, unplug either side of the Otterstat.

If fans are NOT running the Otterstat is bad (assuming engine coolant below ~200F).
If fans are running the fan relay (or aftermarket fan system, or wiring) is bad.


http://www.specialtauto.com/delorean-parts/images/ac-pressure-cycling-switch.jpg[/URL]

He has 2 versions. One for r-12 and and one for r-134a. If I still have the r-12 version in there could this be the culprit?Technically you should change it out (later..one thing at a time. The cut-in/out differences between the two is not the problem...).

[Farrar]

Here's my "Fan Fail Fix."

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Farrar


Here's my "Fan Fail Fix."

I should add that, in case you couldn't tell from the diagram, this only partly restores the function of the fan fail light -- but I did this mostly to give each fan its own circuit breaker and relay; the fan fail light idea was an afterthought. As you can see from the schematic, the light will illuminate if there is a problem with the relay or circuit breaker, but not the fan itself -- it cannot compare draw like Dave McKeen's new "fail fail" module can. In fact, I am told that if you have newer, lower-power cooling fans you can run the "fan fail" module with no problems. At the time that I was making this circuit for my car, Dave's module was not available, and I am still running OEM fans.

I hope that makes things clearer.

Farrar

[Evildeli]

Thanks for the help guys. First off I was expecting the diagram to end with a symbol of a wallet and some extra $$ signs ;) When I get the smaller things out of the way I would still like to go with Toby's fans and clear the whole fan/electrical thing right up. In the meantime I followed Ron's steps. After I started from cold and blasted the AC at max. The fans came on instantly. When I unplugged the low switch the fans turned off immediately. According to Ron's info that would indicate the switch, unless I read it wrong.

[Ron]

I started from cold and blasted the AC at max. The fans came on instantly. When I unplugged the low switch the fans turned off immediately. According to Ron's info that would indicate the switch, unless I read it wrong.Wrong switch...follow the LARGE hose coming off the engine going toward the drivers side, it runs down and connects to a pipe with the Otterstat (http://store.delorean.com/p-6348-thermostat-switch-otterstat.aspx) in it.

[Evildeli]

Wrong switch...follow the LARGE hose coming off the engine going toward the drivers side, it runs down and connects to a pipe with the Otterstat (http://store.delorean.com/p-6348-thermostat-switch-otterstat.aspx) in it.

Are you saying you think the otterstat is bad?

[Ron]

I'm sorry!...I misunderstood what you meant by "low switch" (blower connection or ???).

I'd say there is probably nothing wrong with your AC/fans.
I see why you had question there. I should of said, "...other than possibly the switch itself" there. But don't let me confuse you (again) by saying this -- If this switch is shorted internally and pressures-temp of the refrigerant are such that the evaporator would freeze over, the compressor and fans would not kick off as they normally should. But again, remember it is not only possible, but very common (and some say ideal) for the clutch to never cycle depending on the temps and/or user settings (test as in post 13, cool outside, cool engine, MAX, doors shut,...be patient waiting on it to cycle out...or just replace it at this point with the 134a style you mentioined earlier).

[Ron]

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