1984 fan resistor location

[Gawernator]

There's a pack of resistors in the driver side engine bay under the cover that control the fan speed. I'm guessing it's different for the early model. My fan doesn't work on the lowest setting but I don't care enough to go through that trouble. Lest I break it more lol

[AKCJ]

Thanks Gaw but from what I can tell the early's are different.

So far I've done a search here and at rennlist, checked clarks, and the haynes manual. Seems like it's some sort of big secret.

[pfarah]

I performed a little research regarding your question and found this post from NORMY out of Ft. Lauderdale, Fla back in Jan 2010. I haven't checked myself yet, mainly due to the weather but I guess its worth a try:

Look under your hood. Now, near the windshield, you will find a thin black plastic "tray" that covers the wiper motor. There is a rubber seal that holds in down at the engine side, and some clips at the windshield side. Remove the rubber seal, and carefully pull the tray from its clips and remove from the car. Now, looking at the wiper motor, look just to the left- there is a square aluminum thing; this is for the air conditioner. JUST TO THE LEFT OF THIS is the resistor block. It is an electrical connector with two screws.

NOTE! VERY IMPORTANT! To remove the resistor block, you have to remove the connector first. But the resistor block is mounted INSIDE the air conditioning duct. If you remove those screws without attaching a string or vice grips or some other method...It will FALL INSIDE THE DUCT and you will wind up using your entire repartoir of profanity several dozen times while you attempt to retrieve it!

[guess how I know this!]]

Anyway, good luck!

N!

[pfarah]

AKJC,

Do you need a copy of the wiring diagram?
I have the 1984 AC Current Flow on hard copy that I can scan and email you if needed.

Patrick

[pfarah]

I found this on Ebay:

[Project560]

Originally Posted by pfarah

So, here's the situation...

The resistor reads 1.9 ohms.
The AC fan relay tests fine, the other fan relay is new.
Both fans run on high when the ac is turned on and when the operating temp is getting close to hot.
The driver's side fan does not turn on when the radiator switch is jumper-ed.
Why does the driver's side fan not turn on low? I've already looked into Clark's Garage; maybe I'm missing something and appreciate any insight.

Hope everyone's Christmas was great! I didn't touch the car today at all and feel a little guilty...

Sorry to dig up this old post. It may have been solved a decade ago many times, but I think I now understand how the cooling fan circuit works for EARLY cars (contrary to Clark’s Garage description). I have done all of the testing outlined and I believe that my system is working as designed, including my fan resistor puck which was the original subject of this post (and very helpful for me to find it).

With the key on and/or engine running and the coolant temperature hotter than the thermofan switch set point on the radiator (just below the radiator hose connection), both fans will run on high speed until the temperature cools below the set point of the thermofan switch. Both fans will also go on full speed when the air conditioning is on.

When the key is off and the temperature is higher than the thermofan switch set point the driver’s side (left) fan will run at slow speed until the temperature cools below the set point. This may not happen often so it is hard to observe unless you turn off the car before the 2 fans on full speed have done their job.

I am so grateful for all of Clark’s Garage content. I wish he was still around so I could thank him for all his amazing work. I am sure he would be open to a small edit in COOL-01.

If I am out to lunch and my driver’s side fan should run before the 2 fans come on at full speed, then I still need help figuring out what is wrong. Thanks!

[originalowner]

Originally Posted by Project560

I think I now understand how the cooling fan circuit works for EARLY cars (contrary to Clark’s Garage description).

Your understanding is correct. I read through the description on Clark's and did not find anything technically wrong, but it is definitely not the clearest wording.

Also, I checked the factory wiring diagram and found that the color of one of the wires to the resistor in the photo at the beginning of this thread (re/ye) does not match the schematic (gn/ye). Yet another schematic error is uncovered.

[Monkey Wrench]

I think an old way to limit the speed of a fan was just to waste electrical power by adding resistors, the resistors add a voltage drop so a 2 wire fan can run at below 12 V if in series with a resistor.. add more resistance and you have slower speeds.. its electrically wasteful.. heating a resistor only to slow down the motor.

some of the newer fans may have more windings so then it's able to switch in more windings. that's more electrically efficient.

old volvos from the 80's used resistors, replacement fans dont use them, there was somewhat of an upgrade. If I remember right the later ones used a 4 speed fan , to upgrade you change the fan and switch.

I noticed in my 88 740 it ran all the time on slow, that one only has 2 supply wires ground and hot. I added switch to shut it off in summer. just didn't see any need for that to always be on..

I seem to also have issues with the way its mounted as the water gets down into the motor and rusts the bearings. I'm in the midst of replacing the fan motor in my 740 volvo for that reason just now.

Volvo 740s arent bad, in a 240 replacing the fan is intense, the joke is ,they started with the fan and decided to build a car all around it.. i think it is close to being easier to change the engine than a blower fan in a volvo 240.. I found some shortcuts by cutting through plastic to gain access then using heat tape to patch the cut plastic afterwards. I've done a few in volvo 240's and its never very fun. older ones had bushings, newer had sealed bearings but they both have issues after time.

in the porsch 944 it may be a lot easier to access the fan motor. If it has bushing and you can take it apart and lube it, then it may last longer . i'm not sure if it has bearings or bushings, someone else might know. if you took one apart you'd see which it used. It could change by year , perhaps. a tight bushing may be cured with cleaning and lube, a tight sealed bearing is likely harder to fix in that way. the one in my 740 was so stuck it wasn't worth trying to fix, it rusts where the bushing is retained .. water from above leaks down and fills the motor and that kills them. I tried to fix mine and i was seized up so tight I gave up..

those blower fan motors take down a car in winter, near impossible and dangerous to use the car without one, so it's important.

at the top of this thread there is a picture of a wire-wound resesistor, I think volvo used one like that in the early version of heater blower fan.. the resistor has several "taps" it is divided.

that puck thing looks like it is heat related and perhaps is related to the rad fans and not the heater blower fan. I had to wonder , if it is hard to access and the wires come out, would it be possible to cut the wires and just relocate the ( new) thing and maybe just abandon it there, avoid taking stuff all apart? does it really need to be there or maybe "behind all the dash" was just was a place to hide it?

the green resistor seems like the one Volvo used early on for the heater blower fan. I think I have one I removed since the upgrade to a fan with more wires made it outdated in Volvo..

I thought it might be true that this ( green) one show in the thread was for the heater blower motor and the rest of the thread seems to concern the rad fans. My ford van has one for it's heater blower, its near the switch for the heat fan.. looks different but it's 3 basically wire wound resistors.

[originalowner]

Originally Posted by Monkey Wrench

I noticed in my 88 740 it ran all the time on slow, that one only has 2 supply wires ground and hot. I added switch to shut it off in summer. just didn't see any need for that to always be on..

There is a federal safety regulation that requires positive ventilation at all times the engine is running. This requirement was put in place because too many people were dying of carbon monoxide poisoning when there was an exhaust leak. Modern cars are incredibly safe compared with '50's cars because when people die or are injured in significant numbers, changes are made to the manufacturing requirements in order to prevent future occurrence. Things like seat belts, airbags, collapsing steering columns, visibility requirements, braking systems, etc. were implemented because of dead people. My advice is don't get yourself dead by deactivating safety stuff.

[Monkey Wrench]

thanks for that, i never considered the blower fan to be a safety requirement, That's interesting.
ive seen the motor in my 740 fail more than once due to the under dash position, and leaks from under the grill between hood and windshield into the motor. I was finding the motor partly submerged by water which was being contained by this ducting.
it has a vent hose that leads into the ducting from around the motor. Lat time i just left that off so if it got wet the water had a way out and onto the floor as it seemed to be trapping water within the covering.
ill remove the grill so I can see from the top and maybe seal it up better from the topside too. there may be a plastic cover to shed water and maybe its damaged or full of debris, or something.
I think most of the problem was with the seal around the motor, the OEM one has a different motor flange so Il make it fit and seal it up with windshield goop.
ill try to reconnect the vent hose. maybe its better as the vent may help dry it up if it runs continuously.

I wasn't in a rush except today my newly replaced Volvo 240 master cylinder leaked all its fluid on my way on to work today.
Pedal felt low and then i found a constant drip from between the master cylinder and brake servo. it actually emptied the whole reservoir, it came with a new reservoir too so who knows.. maybe the new seals on the new reservoir leaked or maybe the piston seal was just no good..

I guess the rock auto 18 dollar closeout special wasn't such a deal so I got a new one on order for tomorrow's fun. Ill throw the volvo wagon on the road and bide a bit of time to bleed brakes etc on the volvo sedan..

had a look again at iunch,, yes I think the new volvo master has a bad seal between the new reservoir and the master cylinder.. it was still pushed down tight. i put some tie wraps anyway, maybe they will hold it tighter..
Il fill it and nurse it home carefully, then deal with it properly.

the master cylinder looks a lot lie the 944 one, bit different angle on the line fittings.. I have a new one in hand ready to go in my 944 too. thought Id replace that in the 944 before I go far with other stuff.. Calipers are stuck and need servicing anyway..

I think Ill start to tie wrap the things down to prevent the seal between master and reservoir from separating. maybe that's the issue, I put a bucket under it.. didn't want to get into it at work..

speaking of dangerous, you'd think they would use a more positive seal between the reservoir and the master cylinder.. the volvo one just pushed down on top.. not sure if that's a danger in the 944 but Ill certainly be more aware now. i think when I compared the two it was similar but different sized holes. i think the 944 has one larger and one smaller. volvo has 2 the same size.. very similar in design so I think same "could " happen to a 944 causing suddenly empty.

in my volvo 122 s since it is single circuit, so some put a float thing with an alarm, so that if fluid gets too low, alarm sounds.. Not bad idea.

the float and the idea, was taken from some other car that has the float switch device.. I dont know what car uses one.. but good idea.

I ordered a new master for the volvo, it'll be at the door tomorrow, it appears the problem was just the bottle seals though,, the top of the master cylinder. they leaked. the reservoir is new and didn't come up or off from the master cylinder.. ... I tie wrapped it down anyway..
maybe the new master will at least have a new set of those seals. I'll pull it off when I'm home.. need to fix that up properly and then bleed brakes again..

it was wet under the bottle so it appears it wasn't the piston seals that leaked. ( then it would be wet lower down) when it failed recently it was bypassing internally,, the pedal slowly went down.. i think that's ok now..

I wonder if there is some sort of glue one could put on the seals that is brake fluid compatible.. I cant blame my new 18 dollar master , except those seals were new too and the bottle was installed already It appears it was just that rubber seal connection which seemed to be the fault area. - causing no bloody brakes !

[Monkey Wrench]

if there is a "mode" where motor is supposed to run slow, and if it is the case that a resistor is switched into circuit to slow the motor, that would mean the resistor is in series with the motor. If the resistor then broke, went open circuit, since it's in series with he motor , then you would have no slow speed

- if resistor open and wired in series with motor, then its' an open circuit.
if motor has slow and high speed windings, that's different.

we might not know the actual value of the resistor in ohms and in watts, I suspect that you could pick up a resistor like this at a local parts distributor,,

https://www.ntepartsdirect.com/ENG/CATEGORY/RESISTORS_POWER_WIREWOUND_CERMET

often people will ( incorrectly) call them "cement" resistors but the reference is actually to the brand "Cermet". if you want to , you can string them in series or parallel , for example if you put two in parallel you have half the resistance, if you put two in series you double the rsistance.

if you put 4 in series/parallel you have the same resistance but 4 x the watt rating since you are dividing the load , and heat dissipation up between them all.

i think if the ohms are approximately correct the wattage rating would need to be high enough, but likely if you went ahead and tried a higher watt one , that would probably be ok.. I dont know how you'd calculate the amp- load, or number of watts its handling,, other than by measuring it in circuit.

if you suspect the temperature activated switch you could likely bench test that at different temperatures.. maybe it's possible to be able to check it without first needing to pull the dash all apart ?

a little off topic but i was parked beside a guy that had his fans going on and off on and off , they would only run for 10 seconds.. and I experience that in my van when its on AC. it seems to be constantly cycling on and off, why ? because it is low in AC gas charge ? . Not sure..

[Monkey Wrench]

im of no help with the location, id just say that the resistor you are looking for, for the heater fan is likely not far from the fan wiring, if it exists. since the resistor creates heat it might be located where the heat can be dissipated. the green multi section wirewound resistor looks just like the one volvo used in the heater fan arrangement, but was updated with a different switch and different motor, eliminating the resistor in the "upgrade" .. If the blower motor quit, people would normally change both the switch and the motor, and then there would be no resistor , to find.

if you can go here, it shows the old and the new "system" side by side. That's Volvo but maybe porche did similar, I don't know if that is the case.

https://www.ipdusa.com/products/22228/Blower-Motor-Update-Kit-140-200-73-93-Aftermarket-Volvo-1323849-1370240-9131943

I did just find this video, by Pelican showing the resistor location.. , maybe that solves it?
watch this :
https://www.youtube.com/watch?v=rplsRvJ5mR4&ab_channel=PelicanParts