Radiator fan

[VisPacem]

Hello

It would seem that a pernicious problem might be coming too light in my cooling system, specifically the activation of the radiator fan.

1st. incident: Outside temperature 102F +
Traffic : stuck
A/C quits and blows HOT air
Radiator fan only comes on low speed with A/C on
Fan switch blamed for failure, replaced

2nd incident: Install low temp fan switch: totally useless, fan constantly on and off high speed, rendering A/C completely ineffective. Fan switch replaced with new OEM spec part.
Fan came on High speed once after engine turned off.
No other detected behaviour.


3rd incident: July 2009: Drive across desert, A/C on outside temperature approx: 102F+/ Speed 70mph +
No overheating.No problem. Fan on low speed (as it should)

Next day drive by California beach: outside temperature : low 80s
Traffic typical California, touch and go; A/C OFF. Water temp climbs past LED near top mark on gauge. Independent VDO gauge indicates 205F/201F ++
fan does NOT come on, not on low speed, not on medium speed not on high speed.

Use my override manual switch, the old finger strikes again, fan comes on high speed everything cools down.

Drive back to Vegas, estimated outside temperature 110F. A/C on no problem.

My point being it would seem that as long as I have air flow, I have no overheating problem.
The fan is not coming on as it should.

Question: Why ?
What?
proposed solution(s)

Can three fan switches be bad?
I'll answer that one myself: Why not

Can there be another problem?

I did a search and read about relays and so called resistor packs but nothing addressing my question clearly.

One last thing I give up.
***Please feel free to ask me why I use the A/C, why I go to the beach, if the override switch is metal or plastic, chromed or black, and why do I MUST have a nice Bearnaise with my Chateaubriand. Please go ahead it will give you a chance to blow your own horns, those on your heads of course.***

***This only concerns a few who will recognize themselves quite easily


well that's it for now

Hip hip ....
_________________
LG aka VisPacemPB, *The* party Pooper

No Regrets (Nothing to do with Vanagons)

[crazyvwvanman]

This sounds like a bad low speed fan resistor. Here is my theory.

The fan has 3 speeds. High and low are triggered by the radiator temp switch. Low and medium are triggered by the A/C. Even though low is dead because that part of the resistor is dead, medium is probably still working when the A/C is on. When the A/C is off, you have no fan until high speed is triggered. So you run cooler with A/C on than when it is off because A/C uses medium speed.

High speed also turns off the A/C compressor, as you know, from the folly of the 75 degree temp switch.

High speed is a direct wire with 12v to the fan motor, no resistor.
Low and medium go through giant resistors to drop the voltage and run the fan slower. The low speed resistor burns out because it runs whenever the A/C is on and also when the radiator get hot. If you live where A/C is used a lot the resistor low speed section gets used a lot too.

$40 part, VanCafe. This is 2 resistors built into one package.

Mark

[Wildthings]

The fan is supplied by at least two different fuses. One supplies the low and medium speed power and another supplies the high speed.

Finding defective switches is not unusual, they don't last all that long. The fan switch needs to match the thermostat opening temperature. If the temperature setting of the fan switch are at or above the thermostat opening temperature the fan will be very delayed coming on, while if the fan switch setting is 15° or so lower than the thermostat opening temperature the van will run very frequently.

I carry a pre-made up jumper wire for my fan switch. If the switch fails I can just pull the plug and install the jumper.

[crazyvwvanman]

High speed uses both fuses. Since high speed works, both fuses are good.

Vw made about 1,000,000 watercooled Vanagons of various types and engines. AFAIK, these used 87 degree thermostats and 90+ degree radiator switches. Those fools.

Mark

[Wildthings]

Since you have about a 10-15° drop as the water makes its first pass through the radiator to reach the fan switch, if you are using a 87° thermostat and a 89° fan switch the engine will have to increase in temperature more than 10° before the fan will kick on. This is stupid in my book. Seems to make way more sense for the fan to cycle every minute or two instead of waiting 5-10 minutes and then having to run several minutes to get the temperature to drop, and still leaving it well above what it would be if the van were moving. Just because VW designed something doesn't mean its the best. They did make at least two changes in the fan switches during the Vanagon run, lowering temperatures each time. Have no idea what fan switch they ended up with on the later SA Vanagons.

BTW, in his 3rd Incident, he said that neither high or medium or low were working. Don't know where he gets his power for his added switch.

[Dingchowping]

Hi VisPacem,

I concur with crazyvwvanman, it sounds like its your 1st/2nd stage resistor. I was dealing with almost the same symptoms as yours. I put a new resistor pack in today, problem solved. Keep in mind the 3rd stage (high speed) is the cooling system's last ditch effort to get temps under control. As such whenever the 3rd stage kicks in power to the a/c compressor clutch is cut off, thus reducing load on the engine and eliminating an additional heat source in front of the radiator (the a/c condenser).

In stop and go traffic there's insufficient airflow across the condenser to cool it without the fan...a/c can't do its job without the gas being cooled in the condenser. When the fan finally comes on at high speed the a/c clutch is disengaged until the fan turns off, at which point the a/c clutch re-engages and the now cool condenser provides effective a/c...for about 30 seconds, then the condenser gets heat soaked and you're back at square one. Once traffic clears up and you're moving through the air consistenly the condenser can cool off and you get your a/c back, plus that airflow across the radiator keeps the coolant below the 3rd stage trigger temp.

Pull your driver's side headlight out and take a look at the resistor. I'm willing to bet it's burnt. Often times when these fail there are visual signs...mine was charred in places and the outer wrap was melted away. These things get HOT!

TTFN,
Adam

[VisPacem]

I do appreciate all the answers and comments. To simplify things and knowing for a fact that the fan works, that is when activated by the A/C switch or the faithful finger via the override switch and that it does not work other wise, it would seem that 3 components have or may have a role in activating said fan as required by OEM specs.
1- the relay
2- the thermo switch
3- the resistor pack

My temptation would be to replace all three, but then I would not know which failed.
The learned and doct comments would indicate failure of the resistor pack or the thermo switch or both.
Should replacement of the relay be also considered.
Should both thermo switch and resistor be considered or one or the other ?

recommendations please?


Thanks
_________________
LG aka VisPacemPB, *The* party Pooper

No Regrets (Nothing to do with Vanagons)

[Wildthings]

[shenan-agon]

First of all, pull the wiring clip off the temp sensor at the radiator and jumper the wires, one pair at a time. One combo should turn the fan on low speed, another high speed (the third won't do anything). If that works, the problem's in your sensor. If you're just getting high speed, it's probably that resistor behind your driver's headlight. Mine had the same symptoms, and I was able to just resolder the connections on the big green resistor and I was good to go.

[boardshorts]

My fan stopped working and the fuses are ok.Following along this thread,when I jump the wires at the rad. switch,I get no fan activation,even thought I have power at the fan.Can I assume the fan itself is bad? Has anyone installed an aftermarket fan to replace the stock fan, or should I just cough up the $365 for a new fan?

[Wildthings]

$120 plus shipping.

http://busdepot.com/details.jsp?partnumber=251959455G

[James 93SLC]

[Wildthings]

[VisPacem]

[Wildthings]

[jimbelmont]

[boardshorts]

I have a/c on my 88 Camper,so I need this motor: http://www.van-cafe.com/home/van/page_555_668/fan_assembly___see_description.html Has anyone seen it cheaper?Has anyone used an aftermarket fan, or had this one rebuilt?

[gargo]

It's easy enough to follow the wiring diagram in the Bently, there are a couple of relays in there for the different speeds and possibly one of them is fried?

With A/C you have three stages, one goes through the entire resistor, two runs through 2/3 of the resistor and the last stage has no resistor in line.

Without A/C you have only two stages, one through the resistor and one not.


On my '91 with A/C the resistor was basically disintigrated. $45 from VW 10 minutes to change out.

[VisPacem]

Well then , first I would like to sincerely say thank you to all who responded. Problem now solved. My assumption is that the "resistor pack" was fried or defective, however for peace of mind and to avoid delays, I also replaced the thermo switch.

Now to hijack my own thread, I'll refer to the posts relating to the price asked for radiator fan motors, for a 2.1 with A/C.

Basically after shipping, pretty much 400 big ones. That is crazy, insane and gouging ***in my opinion*** and I am not interested in the lame justification of anyone who wish to cover themselves with ridicule trying to justify this atrocity.

How much can a stupid electric motor be really worth ?

Anyway, someone mentioned using a Ford Taurus fan. I am considering using a Mercedes fan. Small, flat and hyper efficient. One of those finally managed to keep my Austin cool in my corner of the desert, not an easy task.

and..... I can get as many as I want at the local Pig a Part for a bag of peanuts.

Any suggestion greatly appreciated.

nb. As it will not fail that some wise guy will ask why I want replace the fan, simple.. it's a screamer specially at the lower speeds, which to me indicates imminent death , failure of bearing. One more thing it seems a lot of work to remove and re-install or am I wrong ?

anyway thanks in advance
_________________
LG aka VisPacemPB, *The* party Pooper

No Regrets (Nothing to do with Vanagons)

[spiros]

I a going to replace my T3's radiator fan in a couple of hours. As mentioned in the Bentley manual, i will try to do the swap without draining the coolant from the system, but lowering the complete radiator and fan assembly for it.

My fan has a part number on it 251 959 455 G. the one i am receiving in a couple of hours hopefully has the number 251 959 455 M. I am expecting to receive a 450W motor instead of the supposedly 250W one that is on now. Trying to solve some temperature issues here..

The only online source i found indicating the 250W value of the 251 959 455 G motor is at a chinese website http://www.jarparts.com/en/Part/33402/251959455G.html

The 251 959 455 M is the one sold for models with AC and i exect it to be 450W as i was told.