welp, only ever a maximum of 8volts from the output of the 3pin rad sensor for the fans =(
07-16-2008, 02:24 PM
#1
AudiWorld Expert
Thread Starter
Join Date: Mar 2003
Posts: 31,531
Likes: 0
Received 0 Likes
on
0 Posts
welp, only ever a maximum of 8volts from the output of the 3pin rad sensor for the fans =(
I'm assuming it's supposed to be 12v. the fan speeds will activate if jumpered from the connector. My problem is that neither fan speed works at all...at least not when the temp gauge says it's supposed to. Which is why then I started to suspect may the MFTS was screwball, and for a while I've been watching & comparing numbers/indications between CH51 and the gauge. CH51 consistently reads 20*C low, so that would mean the head sensor is screwy. So I take a resistance measurement @ 100*C (as per gauge...CH51 would never get to 100) and it gives me 214ohms, which according to SJM is just about right; they say @ 100C it should be around 200.
So at this point i'm fairly perplexed. Every signal and measurement contradicts one-another so it's really hard to isolate any one piece...hell, it could be all of them for all I know! I'm definitely going to replace the 3pin fan switch so at least that hopefully buys back my cooling fans (trucking up the Coquihalla toll-booth hill in 40*C started to get really sketchy about half way =( .. if I had known my fans were actually ****ed I would have at least jumpered the low-speed on prior to the drive; RS2 fan mod style.
I think I will also replace the 2pin coolant sensor in the head. With any luck maybe this will make CH51 and the gauge jive.
Ok, update, i just finished testing the 2pin sensor again (damn fuggin hot engine bay & exhaust) and only got 150ohms out of it...weird ****, I'm going to presume that sensor as unreliable and move towards its replacement. The car was not at all happy idling/running with that sensor unplugged.
Input or ideas from anyone are always appreciated.
So at this point i'm fairly perplexed. Every signal and measurement contradicts one-another so it's really hard to isolate any one piece...hell, it could be all of them for all I know! I'm definitely going to replace the 3pin fan switch so at least that hopefully buys back my cooling fans (trucking up the Coquihalla toll-booth hill in 40*C started to get really sketchy about half way =( .. if I had known my fans were actually ****ed I would have at least jumpered the low-speed on prior to the drive; RS2 fan mod style.
I think I will also replace the 2pin coolant sensor in the head. With any luck maybe this will make CH51 and the gauge jive.
Ok, update, i just finished testing the 2pin sensor again (damn fuggin hot engine bay & exhaust) and only got 150ohms out of it...weird ****, I'm going to presume that sensor as unreliable and move towards its replacement. The car was not at all happy idling/running with that sensor unplugged.
Input or ideas from anyone are always appreciated.
07-16-2008, 02:29 PM
#2
The head sensor has nothing to do with CC Ch.51. Ch.51 sensor is in the plastic "T" at the back of
the head.
The other thing to consider is the big fan resistor pack in the drivers side fender. Probably easiest to access by taking the bumper off. Something might be wacky connection wise down there.
The other thing to consider is the big fan resistor pack in the drivers side fender. Probably easiest to access by taking the bumper off. Something might be wacky connection wise down there.
07-16-2008, 02:41 PM
#3
AudiWorld Expert
Thread Starter
Join Date: Mar 2003
Posts: 31,531
Likes: 0
Received 0 Likes
on
0 Posts
OOOOOOHHHH... crap. wrong impression and not-so-much clarification by SJM
still though, the head sensor should be accurate. And still the ECU pulls it's "happy information" from there?
So with CH51 still being screwball there's yet another sensor which could be bunged...?
I've eliminated the resistor pack in 3 ways:
First, at the underhood relay stations (#214 = slow speed, #217 = jet engine) I used a jumper to connect the hot sides. Both fans ran at their respective speeds.
Second is that I tested both relays... nice strong clicks with no sticking or hesitation.
Third is what I've been doing today. I pulled the connection off @ the 3pin fan-radiator sensor and then used jumpers across the 3 pins (of the black connector) to simulate 12v being switched to either pin. Both fan speeds activated appropriately and I also heard both relays click.
What I just got finished doing was used some extension wires to connect each hot lead (2) of the 3pin connector to the sensor. This would mean that the sensor has/had the ability to demonstrate it's functionality. On the 3rd pin of the sensor I branched a lead of wire long enough so that I could get my multimeter on it from just under the bumper. I then ran the car until the coolant gauge read 90...no fans, and about 5v showing on the test lead of that sensor. Got her to heat up to 100 (12'oclock position) and still no fan (as previous...this is where jet-engine is supposed to activate) and only 8V showing out of the sensor.
My assumption is it needs more like 12v to activate the fan system/relays?? This doesn't make sense because usually you want a small voltage to trigger the bigger voltage in & through the relay. I dunno what the deal is. My dad has -back at home- an instrument with variable output voltage, so if i had that I could pin-point what's needed to trigger the relays.
arrgh, I really enjoy this investigative electrical stuff, and I mostly have all the instruments to do it. But sometimes and after a while it becomes very frustrating. I'm *ok* with electrical but sometimes don't know how to interpret the readings, and often I don't know what forms of measurements/tests I want to do in order to diagnose a particular problem.
any of this make sense Dave?
So with CH51 still being screwball there's yet another sensor which could be bunged...?
I've eliminated the resistor pack in 3 ways:
First, at the underhood relay stations (#214 = slow speed, #217 = jet engine) I used a jumper to connect the hot sides. Both fans ran at their respective speeds.
Second is that I tested both relays... nice strong clicks with no sticking or hesitation.
Third is what I've been doing today. I pulled the connection off @ the 3pin fan-radiator sensor and then used jumpers across the 3 pins (of the black connector) to simulate 12v being switched to either pin. Both fan speeds activated appropriately and I also heard both relays click.
What I just got finished doing was used some extension wires to connect each hot lead (2) of the 3pin connector to the sensor. This would mean that the sensor has/had the ability to demonstrate it's functionality. On the 3rd pin of the sensor I branched a lead of wire long enough so that I could get my multimeter on it from just under the bumper. I then ran the car until the coolant gauge read 90...no fans, and about 5v showing on the test lead of that sensor. Got her to heat up to 100 (12'oclock position) and still no fan (as previous...this is where jet-engine is supposed to activate) and only 8V showing out of the sensor.
My assumption is it needs more like 12v to activate the fan system/relays?? This doesn't make sense because usually you want a small voltage to trigger the bigger voltage in & through the relay. I dunno what the deal is. My dad has -back at home- an instrument with variable output voltage, so if i had that I could pin-point what's needed to trigger the relays.
arrgh, I really enjoy this investigative electrical stuff, and I mostly have all the instruments to do it. But sometimes and after a while it becomes very frustrating. I'm *ok* with electrical but sometimes don't know how to interpret the readings, and often I don't know what forms of measurements/tests I want to do in order to diagnose a particular problem.
any of this make sense Dave?
07-16-2008, 02:46 PM
#4
G62 info here. The rest requires a "walk" through Bentley's wiring diagrams (I give a look tonight)
<ul><li><a href="https://forums.audiworld.com/s4s6/msgs/148742.phtml">https://forums.audiworld.com/s4s6/msgs/148742.phtml</a</li></ul>
07-16-2008, 02:51 PM
#5
AudiWorld Expert
Thread Starter
Join Date: Mar 2003
Posts: 31,531
Likes: 0
Received 0 Likes
on
0 Posts
i need a bentley. Oh, and i did a fuel pressure regulator replacement today. Are
"new" ones supposed to have a smaller outlet hole (when compared with original) where the fuel returns?
07-16-2008, 08:14 PM
#6
I going to try to describe diagram 72/X100 in the Bentley (1992-93 S4)
There are two sources of power to the fans. One is from terminal 30 on the panel under the steering column. This an always hot (when the battery is connected) line. The other source, "X", comes from the load reduction circuit relay so it is only on when the ignition is on and the starter is NOT engaged. This runs as two separate lines.
The "X" power line is Black/red stripe and runs to terminal 6/85 on the J26 Coolant Fan relay. Draw it on the left. The other "X" input is also black/red stripe and runs to terminal 4/85 on the J135 Third Speed coolant relay (probably the "Jet" speed relay). Draw the J135 on the right.
The Power from the No. 30 always hot line runs through a 50 AMP!!! fuse (S94 - I can't find it's location, sorry). As it leaves the fuse, it runs as three pure red wires, two of them go to terminal 1/30 on the J135 relay. The other red wire runs to terminal 2/30 on the J26 relay.
Concentrating on J26 relay (on the left of the drawing), power leaves the relay from terminal 8/87 as a red wire with a black stripe, running to the N39 fan control(series resistance) - this is the thing that is knocking your voltage down to 8V. From the series resistor, it runs to the fan(s) as a large red wire and then as a red wire to ground (??).
Going back to the J26, the final of the four terminals 4/86 has two wires emerging from it, one brown with white stripe and one brown with yellow stripe. The Br/W goes to the climate control head Terminal 16/16. The Br/Y wire goes down to terminal 2 on the F54 Coolant fan control thermoswitch. (Lower right on the diagram). (We'll come back to that)
Back to the J135 Jet speed relay. On the outlet side, at terminal 2/87 there are two wires one red/black and a large one all black. They run down to a joining point with the wire from the resistor pack and, hence, to the fan(s). This time, there is no resistance to drop the voltage and with two wires, lots of current = jet speed.
The other terminal of the J135 is 3/86 and it is pretty key. There are two wires running from it. They provide the ground that allows the relay to close and provide power to the 2/87 wires going to the fan. One of the wires leaving the 3/86 terminal on relay J135 is Brown/Black. It runs to the F23 A/C refrigerant high pressure switch, i.e. when the A/C is on, the switch closes, allowing current to close J135 and power to flow to the fan(s). The other wire is a Brown/Black and it goes to terminal 1 on the F18 Coolant fan control thermal switch, which on the diagram is part of the F54 Coolant fan control thermo switch.
In both cases, when the F18 or the F54 thermoswitchs are activated (due to heat), they allow current to flow to ground through terminal 3. For the J26 coolant fan control relay, this allows current to flow through that Brown/Yellow to Terminal 2 on the F54 and then to ground, and the relay to be triggered, throwing current through the series resistor and then to the fan. When the F18 thermoswitch is activated, the J135 is triggered and current flows to the fan with out reduction.
Sorry, my scanner isn't working. But that should help a bit. You might want to try to sketch it out.
HTH.
The "X" power line is Black/red stripe and runs to terminal 6/85 on the J26 Coolant Fan relay. Draw it on the left. The other "X" input is also black/red stripe and runs to terminal 4/85 on the J135 Third Speed coolant relay (probably the "Jet" speed relay). Draw the J135 on the right.
The Power from the No. 30 always hot line runs through a 50 AMP!!! fuse (S94 - I can't find it's location, sorry). As it leaves the fuse, it runs as three pure red wires, two of them go to terminal 1/30 on the J135 relay. The other red wire runs to terminal 2/30 on the J26 relay.
Concentrating on J26 relay (on the left of the drawing), power leaves the relay from terminal 8/87 as a red wire with a black stripe, running to the N39 fan control(series resistance) - this is the thing that is knocking your voltage down to 8V. From the series resistor, it runs to the fan(s) as a large red wire and then as a red wire to ground (??).
Going back to the J26, the final of the four terminals 4/86 has two wires emerging from it, one brown with white stripe and one brown with yellow stripe. The Br/W goes to the climate control head Terminal 16/16. The Br/Y wire goes down to terminal 2 on the F54 Coolant fan control thermoswitch. (Lower right on the diagram). (We'll come back to that)
Back to the J135 Jet speed relay. On the outlet side, at terminal 2/87 there are two wires one red/black and a large one all black. They run down to a joining point with the wire from the resistor pack and, hence, to the fan(s). This time, there is no resistance to drop the voltage and with two wires, lots of current = jet speed.
The other terminal of the J135 is 3/86 and it is pretty key. There are two wires running from it. They provide the ground that allows the relay to close and provide power to the 2/87 wires going to the fan. One of the wires leaving the 3/86 terminal on relay J135 is Brown/Black. It runs to the F23 A/C refrigerant high pressure switch, i.e. when the A/C is on, the switch closes, allowing current to close J135 and power to flow to the fan(s). The other wire is a Brown/Black and it goes to terminal 1 on the F18 Coolant fan control thermal switch, which on the diagram is part of the F54 Coolant fan control thermo switch.
In both cases, when the F18 or the F54 thermoswitchs are activated (due to heat), they allow current to flow to ground through terminal 3. For the J26 coolant fan control relay, this allows current to flow through that Brown/Yellow to Terminal 2 on the F54 and then to ground, and the relay to be triggered, throwing current through the series resistor and then to the fan. When the F18 thermoswitch is activated, the J135 is triggered and current flows to the fan with out reduction.
Sorry, my scanner isn't working. But that should help a bit. You might want to try to sketch it out.
HTH.
07-16-2008, 08:40 PM
#7
AudiWorld Expert
Thread Starter
Join Date: Mar 2003
Posts: 31,531
Likes: 0
Received 0 Likes
on
0 Posts
awesome, thanks so much!! I think I could correlate part of the issue using the A/C high pressure
switch.
As far as I recall turning on the air conditioning (from the climate control, obviously) doesn't force the fan on. hmmm... maybe a ground somewhere?
i dunno, it's becoming kinda a hunt & peck situation.
As far as I recall turning on the air conditioning (from the climate control, obviously) doesn't force the fan on. hmmm... maybe a ground somewhere?
i dunno, it's becoming kinda a hunt & peck situation.
Trending Topics
07-16-2008, 09:25 PM
#8
If you convinced the relay are good, the key is in the switches and whether they go to ground when
closed or not, i.e. either the switches don't work or they work and they are not grounding properly enough to trigger the fan relays.
07-16-2008, 10:45 PM
#9
AudiWorld Expert
Thread Starter
Join Date: Mar 2003
Posts: 31,531
Likes: 0
Received 0 Likes
on
0 Posts
the relays have to be working properly because I trigger/test the system as though that lower-rad
3pin fan low-high sensor is working properly... at least by my understanding.
Pin 1 & 2 are live 12v IGN on... i tested that today. #3 is normally open Until the sensor reads coolant temp of 90C. Pin3 grounds/"energizes" Pin2 & the J26 relay clicks, pushes current through to the resister pack, drop voltage & then out to the fan. This cycle shuts off @ like 80C.
If temp gets to 100C then with the 3pin sensor, #3 grounds #1 which throws the J135 relay and outputs large current to the resistor pack but there's no voltage drop and then out to fan.
sorry, this is me thinking out loud trying to rationalize what I measured, saw, and where the breakdown is.
With my jumpers, I just used a solid piece of wire and on the connector went Pin2->Pin3 straight up.. fan goes slow. Pin1->Pin3 things work again, fan goes fast. So that means by taking the 3pin sensor out of the picture the system works -kinda-.
It's possible that internally in that sensor it's restricting transfer of voltage between 3 (ground) and 1-2 (hot lead input). Soooooo, then the relays wouldn't work... When I ran up the engine temps today I was measuring voltage out of Pin3 from the sensor. It rolled up slowly up to a maximum of 8V at 100C..it was 5V at 90C. Maybe I should have been measuring resistance to see if the path is maybe "obstructed"?
I dunno Dave, like I said I enjoy doing this stuff and it's fun for a while, but when you get to a point that you are just taking wild stabs @ issues and coming to the point where you just replace everything I dunno, it gets annoying.
Pin 1 & 2 are live 12v IGN on... i tested that today. #3 is normally open Until the sensor reads coolant temp of 90C. Pin3 grounds/"energizes" Pin2 & the J26 relay clicks, pushes current through to the resister pack, drop voltage & then out to the fan. This cycle shuts off @ like 80C.
If temp gets to 100C then with the 3pin sensor, #3 grounds #1 which throws the J135 relay and outputs large current to the resistor pack but there's no voltage drop and then out to fan.
sorry, this is me thinking out loud trying to rationalize what I measured, saw, and where the breakdown is.
With my jumpers, I just used a solid piece of wire and on the connector went Pin2->Pin3 straight up.. fan goes slow. Pin1->Pin3 things work again, fan goes fast. So that means by taking the 3pin sensor out of the picture the system works -kinda-.
It's possible that internally in that sensor it's restricting transfer of voltage between 3 (ground) and 1-2 (hot lead input). Soooooo, then the relays wouldn't work... When I ran up the engine temps today I was measuring voltage out of Pin3 from the sensor. It rolled up slowly up to a maximum of 8V at 100C..it was 5V at 90C. Maybe I should have been measuring resistance to see if the path is maybe "obstructed"?
I dunno Dave, like I said I enjoy doing this stuff and it's fun for a while, but when you get to a point that you are just taking wild stabs @ issues and coming to the point where you just replace everything I dunno, it gets annoying.
07-16-2008, 11:20 PM
#10
AudiWorld Member
Join Date: May 2005
Posts: 272
Likes: 0
Received 0 Likes
on
0 Posts
S94 location and some helpful wiring diagrams
<a href="http://i13.photobucket.com/albums/a258/maciu/Rekonstrukcja%20Audi%20S4/DSC04414_2005-11-12_17_59_04.jpg">S94 fuse in the background (big image)</a><ul><li><a href="http://www.isham-research.co.uk/quattro/wiring/TypC4/audi_100_klimaanlage_standheizung_mj1997.pdf">cool ing system and A/C (fans on page11)</a></li></ul>