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Here are my notes after studying extensively the hatch pull down unit. If your issue is that you press the hatch release and the hatch comes down and closes after being pushed up by the hatch motor, you need hatch struts unless you have a 92 3rd Gen. In that case you need a new hatch pull down assembly, call Lonsal at Top Down Solutions.
Testing the Hatch Pull down (this is a seperate circuit from the Hatch Release and button in the Console)
From the GM 1988 Shop Manual
1. Check that the connector on the Hatch Pull-down unit is firmly seated
2. Check the LID fuse
3. Check that the Hatch Pull-down Unit case ground is clean and tight.
System Check
1. Open the hatch with the vehicle key and raise the lid. The Striker should rise to the maximum height
2. Lower the Hatch slowly until lock hook on the hatch latches the striker. The stricker retracts, pulling the Hatch closed.
Symptom Table:
1. If the Hatch Pull-down unit functions, but does not close Hatch completely then check the alignment of Hatch Pull-down unit and Hatch
2. If the Hatch Pull-down unit does not operate then Do the Hatch Pull-down Unit Voltage test
Pull-Down Unit Voltage Test
Measure the voltage between the B(Red/White wire) and Ground and the voltage should match the battery voltage.
If Voltage is correct but Hatch Pull-Down Unit does not operate, replace Hatch Pull-Down Unit. Also check the Red/White Wire and LID Fuse for an open.
Circuit Operation:
OPENING
When the hatch is closed, the latch contacts and Striker contacts are in the positions shown on the schematic. Voltage is applied at all times to terminal B of the Hatch Pull-Down Unit through the LID Fuse. When the Hatch is opened, the Hatch lock hook is unlatched from the Striker, moving the Latch contacts from the LATCHED and UNLATCHED position. The motor in the Hatch Pull-Down Unit is then grounded through the UNLATCHED patch of the Latch contacts.
The motor drives the striker upward to prepare for closing. When the Striker reaches the fully extended position, the Striker contacts move to the STRIKER FULLY EXTENDED position, removing battery voltage from the motor.
CLOSING
When the Hatch is lowered, the lock hook latches the Striker, moving the Pull-Down Unit Latch contacts to the LATCHED position. Voltage is then applied to the motor in the reverse direction. The motor moves the Striker down, pulling the Hatch closed. Once the Hatch is closed, the Pull-Down Unit Striker contacts move to the Striker FULLY PULLED DOWN position, removing ground from the motor.
SO, I guess in 1988 they expected you to buy an entire new assembly if there is power from the Red/White wire.
So here are my notes for diagnosing the rest of the hatch pull down unit. (Cont.)
Last edited by Nelz; 10-27-2014 at 10:10 PM.
Reason: fix text
Also, if your problem is that the hatch goes up, then closes and pulls the hatch down when you release the switch, you need new hatch struts unless yours is a 1992 model, in that case contact Topdown solutions or get a new hatch motor assembly.
Components of the hatch pull-down that can go wrong:
1. Relay
2. Striker switch
3. Reversing switch
4. Pull down motor
5. Pull down motor case/guides/gear
-Press the striker switch and see if it clicks
-Apply wires with alligator clips from the battery to the relay
-DVOM to Ohm and look for close to 0
-Big amps = Big terminals Small amps=small terminals
-Power and ground to small terminals, with OHM to big terminals
-Take apart the cap and see if it's corroded inside
-Check the contacts, are they pitted? How much of a contact drop are you getting? Rating from OHM meter and relay should be the same.
Here are how the wires work (testing the striker switch and reversing switch):
www.thirdgen.org/forums/body/703297-hatch-pull-down-help.html
Post #21
There are only 3 connections on the unit harness. Blue (12v+), white (unused with no cargo light) and black(ground) The hatch release is part of the body harness, not the pulldown motor harness. Have you checked for 12v+ at the red wire with white tracer from the body harness? Are you sure your ground is good?
Next, probe the four wire connector just above the motor with the white plug. When you push the lever for the latch switch as though the hatch is closed, the orange wire should be grounded. When that lever is released as though the hatch is open, the white wire should be grounded. If you don't have a multimeter, now is a good time to borrow one or get one. How about a picture of your connections since you keep giving conflicting information on how it is hooked up?
https://www.thirdgen.org/forums/elec...ont-close.html
Post #18
lonsal....I have a 87 Camaro with a power hatch. I replaced the motor and housing assy. a few years ago due to a intermittent problem of the power hatch not raising sometimes and not lowering sometimes. The motor didn't fix the issue. There are 4 wires connected to the reversing switch. The dk blue and brown have 12v and the white and orange have only a few mv. When I depress the switch with my finger to simulate the hatch being closed the voltages stay the same on the dk blue and brown and the mv slightly cahnge between the orange and white. There are 3 wires coming from the switch mounted at the top of the latch mechanism, white, black and orange. I checked for continuty. In the up position the black and white are closed and when the switch is depressed, the black and orange are closed. I carefully removed the relay from the housing to check the contact pads for corrosion and they were clean. I can't hear the relay click when depressing the switch on the latch mechanism however I do get continuty between the center pin and the perpendicular pin when manually engaging the relay. In your opinion from the info given does it sound like the hatch pull down relay or the reversing switch that is causing this intermittent problem? Thanks!
(ISOLATE THE STRIKER SWITCH. DOES IT TRIP THE RELAY? DOES THIS HAPPEN:
When you push the lever for the latch switch as though the hatch is closed, the orange wire should be grounded. When that lever is released as though the hatch is open, the white wire should be grounded. YES? THEN IT'S REVERSE SWITCH OR MOTOR)
Tricks that might work: https://www.thirdgen.org/forums/elec...ont-close.html
Post #28
My trunk lid pulldown stopped working also. Changed the motor and relay. Nothing still worked. Made an appointment to take it in. Same night looking at the fuse block in the manual and the hatch back lid release are on the same fuse as the horn relay. Honked the horn and the
trunk lid pulled right down.
If there are any inaccuracies, please let me know. Or if you've got a better way of testing and isolating which component died, please let me know that too!
If there are any inaccuracies, please let me know. Or if you've got a better way of testing and isolating which component died, please let me know that too!
My "Hatch pulldown mechanism" also doesnt work properly(It won't go down when the hatch is closed). So I tested the "striker switch" white and orange wire as descirbed above and it did work(orange wire was grounded once the striker siwtch depressed and white wire grounded once it was relased),I replaced the relay as the old one was corroded inside, but that made no difference.
But I noticed that the following that might help faster test the motor:
#1-when I grounded the motor housing to a chassis with a short piece of wire, the motor would travel all the way down then loud click was herd fromt the "reverse switch" and the motor would come back UP(proving that motor works)
#2 the striker switch would prevent the motor from coming up when it was held depressed while the motor was going down. The motor would comeback up after the striker switch was released(proving that striker switch works)
I suspect that my reverse switch had gone bad. Plz correct me if am wrong or does any one know how the test the Reverse Switch itself ?
Last edited by judoka_ca; 03-11-2015 at 09:29 PM.
Reason: more info added
What is the white wire for in this picture? The old one was crimped to the yellow wire in the picture but it works properly without it (at least with the key in the lock - the switch doesn't work).
Any chance you have a picture of how it's connected?
The white wire was used from 88-91 as a switched ground to turn on the optional hatch light when the hatch was opened. It was plugged into a black with orange stripe wire. For the 86-87 model years that white wire is unused because the optional hatch light for those years had a manual switch to turn on and off the light.
I have a 92... and had an issue with my pulldown. It raised up, but wouldnt pull down. tested continuity on the reversing switch I Believe>, and i get continuity both directions, the one the hatch actually pushes on to trigger the Down movement.. the motor works both ways... Not sure how to test the last switch taht connects directly to the motor... Hope someone can help.
My latch goes up but won't pull down. After a half hour of testing, I found the plug on the motor loose. If I giggle it, the latch will pull down, but if I stop, it goes back up. As a temporary fix, I got it to go down and then pulled the connector to the plug. Now at least the hatch is all the way down.
I have a 92 and the hatch pull down does nothing. I have a service manual and tried to troubleshoot the best I could. I have power to the plug going into the motor but nothing happens when moving the t switch. Does anyone know how I can test just the motor for 91-92 pull down unit. I did a search and I only find test methods for earlier models. Thanks for any help
10-27-2014, 10:07 PM
