Oil Cooler & A/C Ballast Resistors
06-18-2004, 11:40 PM
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Oil Cooler & A/C Ballast Resistors
So I've confirmed that both are bad. The oil cooler fan only operates on high and the A/C fan cycles on and off ever 10-15 seconds. After reading the p-car DIY page I know they are both things I can easily do myself, but seem quite involved for a simple replacement.
Would it not be possible to simply LEAVE the failed resistor in place, cut the wire and splice it into the new resistor ?? Then, mount the new resistor in a more accessible place ?
I dunno, I'm sure I'm not the first to think of this considering all the previous knuckle-scraping that others have endured, and maybe I'm missing something fundamental about the operation/functionality of these resistors. But, in my searches, I've found nothing to indicate it has been tried before or even discussed - so, I thought I'd throw it out there for those of you more electrically inclined. Whadda you guys think ??
Would it not be possible to simply LEAVE the failed resistor in place, cut the wire and splice it into the new resistor ?? Then, mount the new resistor in a more accessible place ?
I dunno, I'm sure I'm not the first to think of this considering all the previous knuckle-scraping that others have endured, and maybe I'm missing something fundamental about the operation/functionality of these resistors. But, in my searches, I've found nothing to indicate it has been tried before or even discussed - so, I thought I'd throw it out there for those of you more electrically inclined. Whadda you guys think ??
06-18-2004, 11:58 PM
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A few people have already done that, afaik. Just be careful where you mount it
EDIT: In fact, you don't need to splice anything. Just use the existing plug to connect the new resistor.
EDIT: In fact, you don't need to splice anything. Just use the existing plug to connect the new resistor.
06-19-2004, 12:40 AM
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Originally posted by graham_mitchell
A few people have already done that, afaik.
A few people have already done that, afaik.
Here's your old post on the subject:
fan resistor DIY stopped dead by corroded bolt.
06-19-2004, 12:44 AM
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Hi Luke..!
Removing either the oil cooler or the A/C doesn't require removing the front bumper cover. So - it's pretty easy access to the ballast resistors, which are mounted to either shroud with, as I recall - a 4mm hex screw. However - you will have to remove:
- The front wheels;
- The front forward wheel liners;
- the splitters;
- the lower and top mounts nuts (13mm)
- the mount stay
- and the rubber hold offs.
Once those are loose/out - the cooler & A/C fan shrouds will drop low enough to access the ballast resistors. When you do that - there is about 8" of wire tail on the resistor that ends with a round plug. Simply unplug the old - and plug in the new into the same connector after remounting the new ballast resistor onto the shrouds.
HTH,
John
Removing either the oil cooler or the A/C doesn't require removing the front bumper cover. So - it's pretty easy access to the ballast resistors, which are mounted to either shroud with, as I recall - a 4mm hex screw. However - you will have to remove:
- The front wheels;
- The front forward wheel liners;
- the splitters;
- the lower and top mounts nuts (13mm)
- the mount stay
- and the rubber hold offs.
Once those are loose/out - the cooler & A/C fan shrouds will drop low enough to access the ballast resistors. When you do that - there is about 8" of wire tail on the resistor that ends with a round plug. Simply unplug the old - and plug in the new into the same connector after remounting the new ballast resistor onto the shrouds.
HTH,
John
06-19-2004, 08:09 AM
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Hi , I changed both of these recently, its not fun, but its not impossible. Like John D says, you dont need to remove the bumper, but you will need patience.
I originally was going to put them in a more accessable spot, but first I checked how hot they get when operating.... lets just say very hot, so i decided maybe the factory mounted them where they were for good reasons, not next to painted surfaces etc, ( as well as for ease of construction when building the car). Cheers Lyndon
I originally was going to put them in a more accessable spot, but first I checked how hot they get when operating.... lets just say very hot, so i decided maybe the factory mounted them where they were for good reasons, not next to painted surfaces etc, ( as well as for ease of construction when building the car). Cheers Lyndon
06-19-2004, 08:45 AM
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Luke,
I replaced my resistors when I got my car as precaution since I knew they could be a problem.
I removed my front bumper to do this job. It comes off and goes on easily, ie. technically not difficult. I could have changed the resistor on the A/C condensor pretty easily, but the one on the oil cooler looked like it would be a pain to get to.
I replaced my resistors when I got my car as precaution since I knew they could be a problem.
I removed my front bumper to do this job. It comes off and goes on easily, ie. technically not difficult. I could have changed the resistor on the A/C condensor pretty easily, but the one on the oil cooler looked like it would be a pain to get to.
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06-19-2004, 12:07 PM
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Ron, I too removed my front bumper to do the job. The Turbo/4S/2S front bumper does not have the removable lower-corner panels as does the standard front bumper.
max
max
06-19-2004, 03:26 PM
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I think the best solution is where you simply modify the RELAY to bypass the slow setting and taking the faulty resistor out of the loop all together.. I did that, saved money by not buying a new resistor and now the fan just comes on full at low temps and full at high temps.. search for the post on how to mod the relay. kind of an elegant mod. I just have to get rid of the dead weight of the faulty resistor now ;-)
Coleman,
Coleman,
06-19-2004, 06:06 PM
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Coleman - I can't seem to find the thread that outlines the relay mod, do you happen to have it ? I agree with you however, fast speed only coming on in place of the slow speed would be better.
Thanks to all for the helpful posts, you guys are a wealth of knowldge and experiance, much appreciated...
I think I'll remove the bumper just for fun to take a closer look at everything up there and do some cleaning while I'm at it. If these resistors generate so much heat, wouldn't it be a better idea to mount them in a place that is not so starved for space ? Or, does the factory mounting position get plenty of airflow ?
I was contemplating mounting them on the inside of the fender liner. Yes removal of the liner would be a bit tricky...you'd have to remember the resistor is mounted on the other side of it before yanking it out. Plus, I'm the only person whose ever going to be removing it... No real functionality problem there and I assume the inside surface of the fender liner gets plenty of fresh air...
Thoughts ?
Thanks to all for the helpful posts, you guys are a wealth of knowldge and experiance, much appreciated...
I think I'll remove the bumper just for fun to take a closer look at everything up there and do some cleaning while I'm at it. If these resistors generate so much heat, wouldn't it be a better idea to mount them in a place that is not so starved for space ? Or, does the factory mounting position get plenty of airflow ?
I was contemplating mounting them on the inside of the fender liner. Yes removal of the liner would be a bit tricky...you'd have to remember the resistor is mounted on the other side of it before yanking it out. Plus, I'm the only person whose ever going to be removing it... No real functionality problem there and I assume the inside surface of the fender liner gets plenty of fresh air...
Thoughts ?
06-19-2004, 08:49 PM
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You can find my noninvasive relay jumper here, terminals #1 to #6 in the relay plug. Others more motivated than myself have modified the relay internally (also described in this thread).
Relay Jumper = Fast Instead of Slow Speed Fan
Relay Jumper = Fast Instead of Slow Speed Fan
06-20-2004, 12:47 AM
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I used an external jumper partially because I didn't want to modify a good relay, mainly because I was too lazy to get out the solder iron. Oh, and I misspoke earlier--it's a 1.9 ohm resistor, not 1.7 ohms.
With the A/C on, condenser fan running, there's 0.262V across the resistor. So, 0.14A. Which is about what I expected, considering that there is a 75 ohm resistor between 86 & 85/85c, internal to the relay >> 12V/75 ohms = 0.16A. The 1.9 ohm resistor does little to affect the series resistance.
You don't have to use a (low-value) resistor like I did, if you don't have one. You can simply use an insulated wire. Since I had it, I used the resistor. For a few reasons. Because the majority of the exposed area was insulator, and not "hot" wire. The wire ends were nice and rigid, making it easy to shove 'em in the relay slots. And, if the jumper wire was to (for some strange reason) ever connect 12V directly to ground, there would be some limit on the current.
I imagine you can also jumper 85/85c internal to relay (similar to what you did for 87/87c). Haven't tried it myself.
As you know, this jumper won't make the oil cooler fan run continuously. But, it will run the fan in fast-speed, whenever the relay receives a signal to start the fan in slow-speed. As you saw when your oil temperature got to about 9:00.
Incidentally, if you're going to leave your relay modified, there's no point in replacing the 0.450 ohm ballast resistor. As I described earlier, the jumper will cause the resistor to be shunted. Conversely, if you replace the ballast resistor, and want slow-speed functional, you'll need to remove the jumper. But, I suspect you know this already.
With the A/C on, condenser fan running, there's 0.262V across the resistor. So, 0.14A. Which is about what I expected, considering that there is a 75 ohm resistor between 86 & 85/85c, internal to the relay >> 12V/75 ohms = 0.16A. The 1.9 ohm resistor does little to affect the series resistance.
You don't have to use a (low-value) resistor like I did, if you don't have one. You can simply use an insulated wire. Since I had it, I used the resistor. For a few reasons. Because the majority of the exposed area was insulator, and not "hot" wire. The wire ends were nice and rigid, making it easy to shove 'em in the relay slots. And, if the jumper wire was to (for some strange reason) ever connect 12V directly to ground, there would be some limit on the current.
I imagine you can also jumper 85/85c internal to relay (similar to what you did for 87/87c). Haven't tried it myself.
As you know, this jumper won't make the oil cooler fan run continuously. But, it will run the fan in fast-speed, whenever the relay receives a signal to start the fan in slow-speed. As you saw when your oil temperature got to about 9:00.
Incidentally, if you're going to leave your relay modified, there's no point in replacing the 0.450 ohm ballast resistor. As I described earlier, the jumper will cause the resistor to be shunted. Conversely, if you replace the ballast resistor, and want slow-speed functional, you'll need to remove the jumper. But, I suspect you know this already.
I really like this solution. Let me try to get this straight in my mind, so please indulge me
.....- If I do this jumper mod, I could leave the dead A/C resistor where it is ...no harm no foul? (and no scraped knuckles!!)
- The original signal to trigger low speed fan at the condenser will now just trigger high-speen fan instead...no other changes?
- I know you said using the resistor is not "necessay," but in your opinion is using a piece of insulated wire potentially detrimental in any way? Is it worth it for me to get the resistor as I really doubt there is any way for a 2cm jumper wire is going to ground out when connected to the relay.
- Curious about the oilcooler: I already have a manual switch and use it often in traffic so am really just wondering...Is 9:00 on the guage about where the slow speed should start? If so, when does the highspeed supposed to kick in?
Thanks a bunch, Randall! You're truly a great resource, esp on A/C issues!
Edward
06-20-2004, 03:15 AM
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Hey Edward,
>- If I do this jumper mod, I could leave the dead A/C resistor where it is ...no harm no foul? (and no scraped knuckles!!)
Yup, as you suspect, you're simply abandoning the slow-speed circuit in place, using the fast-speed circuit exclusively.
>- I know you said using the resistor is not "necessay," but in your opinion is using a piece of insulated wire potentially detrimental in any way? Is it worth it for me to get the resistor as I really doubt there is any way for a 2cm jumper wire is going to ground out when connected to the relay.
The resistor isn't necessary, no problem with just using an isulated wire. I mainly used it because the wires on either side of the resistor are rigid.
>- Curious about the oilcooler: I already have a manual switch and use it often in traffic so am really just wondering...Is 9:00 on the guage about where the slow speed should start? If so, when does the highspeed supposed to kick in?
Yes, just a little over 9:00 is when the slow-speed fan should start. To be honest, I don't know when the fast-speed oil cooler fan is supposed to kick-in on a 993. It's 239F for a 964, I've never seen the value for a 993.
>- If I do this jumper mod, I could leave the dead A/C resistor where it is ...no harm no foul? (and no scraped knuckles!!)
Yup, as you suspect, you're simply abandoning the slow-speed circuit in place, using the fast-speed circuit exclusively.
>- I know you said using the resistor is not "necessay," but in your opinion is using a piece of insulated wire potentially detrimental in any way? Is it worth it for me to get the resistor as I really doubt there is any way for a 2cm jumper wire is going to ground out when connected to the relay.
The resistor isn't necessary, no problem with just using an isulated wire. I mainly used it because the wires on either side of the resistor are rigid.
>- Curious about the oilcooler: I already have a manual switch and use it often in traffic so am really just wondering...Is 9:00 on the guage about where the slow speed should start? If so, when does the highspeed supposed to kick in?
Yes, just a little over 9:00 is when the slow-speed fan should start. To be honest, I don't know when the fast-speed oil cooler fan is supposed to kick-in on a 993. It's 239F for a 964, I've never seen the value for a 993.
06-20-2004, 09:07 AM
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Re: Oil Cooler & A/C Ballast Resistors
Originally posted by Agro1
.......But, in my searches, I've found nothing to indicate it has been tried before or even discussed ..............
.......But, in my searches, I've found nothing to indicate it has been tried before or even discussed ..............
https://rennlist.com/forums/showthre...threadid=95672
https://rennlist.com/forums/showthre...hreadid=134619
https://rennlist.com/forums/showthre...hreadid=139083
https://rennlist.com/forums/showthre...hreadid=132554
by the way, I didn't remove the front bumper since I don't want to mess with that rubber seal inbetween the bumber and the fender.