kickdown relay test?
07-27-2002, 06:56 PM
#1
5th Gear
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kickdown relay test?
The kickdown relay is unlike any of the other in my fuse panel so it makes it hard to take out and swap with one that works.. I understand where the switching occurs and this is where one would place probes to see a change in the circuit but what pins receive the positive and negative power from a 12 volt dc source.. I feel my kickdown relay may be bad and don't want to ruin this if its still ok.. the switch underneath the petal and the voltage across the wire to this was all ok. David. 86.5auto.
07-28-2002, 05:34 AM
#2
Dave,
For the precise info on your pin out check:
1. Go to top of page.
2. Click search.
3. Look at boxes, click any date and entire message. Type in kickdown switch, enter.
4. Should be at least 18 post's/topics.
The one you want is 2nd or 3rd from start of the list , Steve C. , a trany guru amongst other things explains all.
Hell, read em' all good or neat stuff.
HTH
John S. and Pattycakes <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
For the precise info on your pin out check:
1. Go to top of page.
2. Click search.
3. Look at boxes, click any date and entire message. Type in kickdown switch, enter.
4. Should be at least 18 post's/topics.
The one you want is 2nd or 3rd from start of the list , Steve C. , a trany guru amongst other things explains all.
Hell, read em' all good or neat stuff.
HTH
John S. and Pattycakes <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
07-28-2002, 09:11 PM
#3
Rennlist Member
Rennlist Site Sponsor
Most of the relays have a wiring diagram on the case.
In general:
30 - battery voltage
15 - switched battery voltage (usually ignition circuit)
87 - load (usually NO - normally open - contact)
87a - load - (usually NC - normally closed)
85 - ground to the relay coil
86 - power to relay coil
The kickdown relay does NOT operate the kickdown - it defeats it at red line. The idea is that power from the ignition bus runs thru the switch to the relay, and there goes thru the NC contacts of the relay, and then runs back to the kickdown solenoid. At lower engine speeds, the relay does nothing at all. At red line, the engine ECU interrupts the relay, opening the circuit to the kickdown solenoid. This gives instant and very repeatable high-RPM upshifts.
In general:
30 - battery voltage
15 - switched battery voltage (usually ignition circuit)
87 - load (usually NO - normally open - contact)
87a - load - (usually NC - normally closed)
85 - ground to the relay coil
86 - power to relay coil
The kickdown relay does NOT operate the kickdown - it defeats it at red line. The idea is that power from the ignition bus runs thru the switch to the relay, and there goes thru the NC contacts of the relay, and then runs back to the kickdown solenoid. At lower engine speeds, the relay does nothing at all. At red line, the engine ECU interrupts the relay, opening the circuit to the kickdown solenoid. This gives instant and very repeatable high-RPM upshifts.
07-30-2002, 11:27 PM
#4
Three Wheelin'
Join Date: May 2001
Location: Hudson Valley NY
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The kick down rely A.K.A the speed rely does operate the kick down solenoid. Because the kick down rely is wired with terminal # 87A to the load (kick down solenoid) and terminal # 30 to the power supply (kick down switch under the gas pedal). This relay is closed. The contact is closed, allowing the voltage from the kick down switch (once activated) to flow through terminal #30 though the closed contact of the relay through terminal 87A to the kick down solenoid, which is grounded thus activating the solenoid.
The kick down rely allows the power to flow form the switch (pedal) to the kick down solenoid because the pull down contact is already closed. Remove the rely and you have no kick down. When the kick down solenoid is energized a jet needle opens reducing the control pressure in the valve body, allowing kick down up shifts closed to the red line RPM limitation of the engine. If the engine RPM should ever exceed 5900 +/- 60 RPM the power via the EZK controller, to the kick down rely is interrupted, allowing the transmission to up shift to a higher gear, thus lowering the engine RPM.
Jay Wellwood
Senior User
Rennlist Member
User # 31
posted 08-07-2001 16:54
--------------------------------------------------------------------------------
Randy-
First - please understand that I took no offense to your comments...my experience is undoubtedly not complete as yet....however - if you have been monitoring the main 928 message board - you should find that Wally did poost a response to this particular issue. As such, I passed on what I could remeber - and also suggested that the original poster contact Wally directly.
That being said, I may not understand your comment regarding the shifting modulator solenoid adjustment - since this (as I understand it) changes the shifting 'hardness' but not the speed (engine rpm) at which the shift point occurs.
Please advise - as I am definitely interested in this particular area.
Lastly - I am certain that most would agree with this position - any information gleaned from this list is 'free' and may or may not be the gospel. Mostly by experience and wisdom of others...and may not be the most correct in the eyes of some.
BTW - I searched the archives and found the message....here is is what Wally P at 928 Specialists had to say...
The automatic transmission is primarily controlled by internal hydraulic
pressures. This includes the speed at which upshifts and downshifts occur,
and the firmness of the shifts.
The kickdown solenoid is only one of several devices that adjust the
control pressure to change the shifts. When the kickdown switch is made
(closed), power flows from fuse #10 (on the '87) thru the switch, then into
the 30 terminal of the kickdown relay (XV on the '87), thru the normally
closed contacts of the relay, and out the 87a terminal to the kickdown
solenoid mounted inside the transmission. When the solenoid is energized,
it reduces control pressure, raising the shift speed close to the maximum
speed.
The kickdown relay doesn't do what most people think that it does. The
power flow from the switch to the solenoid is thru the NORMALLY CLOSED
contacts of the relay. This means that the power normally flows thru the
relay. In order to control the shift points more precisely (since the speed
is very close to engine redline), the kickdown relay receives a signal from
the tachometer when engine speed hits 5800 +/-60 RPM (USA and Japan - it's
100 RPM higher for the ROW). This signal open the contacts in the kickdown
relay, breaking the power to the kickdown solenoid. This has the same
effect as instantaneously lifting your foot from the throttle switch,
causing an instant shift. As soon as the engine speed goes back below 5800,
the relay closes the contacts, lowering the control pressure to hold the
next shift.
So, the kickdown switch (and the added parallel kickdown switch) supplies
power to the kickdown solenoid only when the engine speed is below 5800
RPM. Above that speed, the kickdown relay opens, breaking the circuit.
You can check by pulling relay XV (on the '87) and jumpering terminals 30
and 87a in the socket, then driving the car. If there is now a difference
in the shift speeds, relay XV or the contacts for it are bad.
I would suggest that you NOT try the full throttle shift points with the
relay jumpered.
Wally Plumley
928 Specialists
Please advise...as YMMV
--------------------------------------------------------------------------------
Posts: 596 | From: sharkansas | Registered: May 2001 | IP: Logged
steve cattaneo
User
Rennlist Member
User # 478
posted 08-08-2001 22:24
--------------------------------------------------------------------------------
The kick down solenoid controls up shifts and downshifts. In the full throttle kick down mode, theA28 transmission changes it’s up and down shift points, the up shifts are slightly higher than full throttle shifts for maximum acceleration and performance. The other function of the kick down solenoid and tv cable is to force a 2nd to first gear downshift from a dead stop take off. At light and full throttle take offs the USA 928 starts off in 2nd gear.
Governor pressure pushing on the shift valve induces up shifts and downshifts, in a pressure less hydraulic system (the car not moving). The shift valves (in the valve body) are held in the lower gear by a spring. When the car is moving, governor pressure increases pushing the shift valve in opposition of the spring force, causing the transmission to up shift or downshift, depending on throttle position and road speed. The A28 trans has a kick down, downshift safety feature, called the speed relay. Lets say we are cruising at a 100 mph and we want to pass a slower car, while pushing down on the throttle, the kick down solenoid is energized. Thereby causing a 4th to 3rd gear downshift. The engine revs to 5901 rpm. The speed relay (rev limiter) cuts power to the kick down solenoid causing the transmission to up shift back into 4th, lowering the rpm’s below the cut off point. Think of the speed relay as a speed limiter, preventing the engine from redlining, this is the only function of the tach input.
steve c
--------------------------------------------------------------------------------
Posts: 313 | From: new york | Registered: May 2001 | IP: Logged
Jay Wellwood
Senior User
Rennlist Member
User # 31
posted 08-09-2001 09:26
--------------------------------------------------------------------------------
Thanks for the info Steve...definitely interesting stuff.
--------------------------------------------------------------------------------
Posts: 596 | From: sharkansas | Registered: May 2001 | IP: Logged
All times are U.S. EasternTime
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
The kick down rely allows the power to flow form the switch (pedal) to the kick down solenoid because the pull down contact is already closed. Remove the rely and you have no kick down. When the kick down solenoid is energized a jet needle opens reducing the control pressure in the valve body, allowing kick down up shifts closed to the red line RPM limitation of the engine. If the engine RPM should ever exceed 5900 +/- 60 RPM the power via the EZK controller, to the kick down rely is interrupted, allowing the transmission to up shift to a higher gear, thus lowering the engine RPM.
Jay Wellwood
Senior User
Rennlist Member
User # 31
posted 08-07-2001 16:54
--------------------------------------------------------------------------------
Randy-
First - please understand that I took no offense to your comments...my experience is undoubtedly not complete as yet....however - if you have been monitoring the main 928 message board - you should find that Wally did poost a response to this particular issue. As such, I passed on what I could remeber - and also suggested that the original poster contact Wally directly.
That being said, I may not understand your comment regarding the shifting modulator solenoid adjustment - since this (as I understand it) changes the shifting 'hardness' but not the speed (engine rpm) at which the shift point occurs.
Please advise - as I am definitely interested in this particular area.
Lastly - I am certain that most would agree with this position - any information gleaned from this list is 'free' and may or may not be the gospel. Mostly by experience and wisdom of others...and may not be the most correct in the eyes of some.
BTW - I searched the archives and found the message....here is is what Wally P at 928 Specialists had to say...
The automatic transmission is primarily controlled by internal hydraulic
pressures. This includes the speed at which upshifts and downshifts occur,
and the firmness of the shifts.
The kickdown solenoid is only one of several devices that adjust the
control pressure to change the shifts. When the kickdown switch is made
(closed), power flows from fuse #10 (on the '87) thru the switch, then into
the 30 terminal of the kickdown relay (XV on the '87), thru the normally
closed contacts of the relay, and out the 87a terminal to the kickdown
solenoid mounted inside the transmission. When the solenoid is energized,
it reduces control pressure, raising the shift speed close to the maximum
speed.
The kickdown relay doesn't do what most people think that it does. The
power flow from the switch to the solenoid is thru the NORMALLY CLOSED
contacts of the relay. This means that the power normally flows thru the
relay. In order to control the shift points more precisely (since the speed
is very close to engine redline), the kickdown relay receives a signal from
the tachometer when engine speed hits 5800 +/-60 RPM (USA and Japan - it's
100 RPM higher for the ROW). This signal open the contacts in the kickdown
relay, breaking the power to the kickdown solenoid. This has the same
effect as instantaneously lifting your foot from the throttle switch,
causing an instant shift. As soon as the engine speed goes back below 5800,
the relay closes the contacts, lowering the control pressure to hold the
next shift.
So, the kickdown switch (and the added parallel kickdown switch) supplies
power to the kickdown solenoid only when the engine speed is below 5800
RPM. Above that speed, the kickdown relay opens, breaking the circuit.
You can check by pulling relay XV (on the '87) and jumpering terminals 30
and 87a in the socket, then driving the car. If there is now a difference
in the shift speeds, relay XV or the contacts for it are bad.
I would suggest that you NOT try the full throttle shift points with the
relay jumpered.
Wally Plumley
928 Specialists
Please advise...as YMMV
--------------------------------------------------------------------------------
Posts: 596 | From: sharkansas | Registered: May 2001 | IP: Logged
steve cattaneo
User
Rennlist Member
User # 478
posted 08-08-2001 22:24
--------------------------------------------------------------------------------
The kick down solenoid controls up shifts and downshifts. In the full throttle kick down mode, theA28 transmission changes it’s up and down shift points, the up shifts are slightly higher than full throttle shifts for maximum acceleration and performance. The other function of the kick down solenoid and tv cable is to force a 2nd to first gear downshift from a dead stop take off. At light and full throttle take offs the USA 928 starts off in 2nd gear.
Governor pressure pushing on the shift valve induces up shifts and downshifts, in a pressure less hydraulic system (the car not moving). The shift valves (in the valve body) are held in the lower gear by a spring. When the car is moving, governor pressure increases pushing the shift valve in opposition of the spring force, causing the transmission to up shift or downshift, depending on throttle position and road speed. The A28 trans has a kick down, downshift safety feature, called the speed relay. Lets say we are cruising at a 100 mph and we want to pass a slower car, while pushing down on the throttle, the kick down solenoid is energized. Thereby causing a 4th to 3rd gear downshift. The engine revs to 5901 rpm. The speed relay (rev limiter) cuts power to the kick down solenoid causing the transmission to up shift back into 4th, lowering the rpm’s below the cut off point. Think of the speed relay as a speed limiter, preventing the engine from redlining, this is the only function of the tach input.
steve c
--------------------------------------------------------------------------------
Posts: 313 | From: new york | Registered: May 2001 | IP: Logged
Jay Wellwood
Senior User
Rennlist Member
User # 31
posted 08-09-2001 09:26
--------------------------------------------------------------------------------
Thanks for the info Steve...definitely interesting stuff.
--------------------------------------------------------------------------------
Posts: 596 | From: sharkansas | Registered: May 2001 | IP: Logged
All times are U.S. EasternTime
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
