98 S10 Blazer - Rear liftgate Relay

[yeags]

I have a 4 door 98 S10 Blazer, and the rear glass does not open by the switch on the dash, the button on the liftgate, or by the button on the remote. I am also unable to turn the key in the back lock on the liftgate, although the door handle on the liftgate does work fully. I pulled the back trim panel off since I saw numerous other posts regarding the "cheap plastic piece" that connects the actuator to the release lever. This piece is fully in tact, and the actuator does not appear to be frozen or stuck. I put a multi meter on the power connector that goes into the actuator, and it does not show any voltage. I assumed this meant that there is either a short in the line somewhere (there are no blown fuses), or a bad relay. Problem is... I can find a part listed as a "Rear liftgate Relay" that is available, but I can not find any listings of where that relay might be located. Can anyone help me with this one?

[wirenut699]

Welcome to AF

I have a 1999 blazer which is very similar but may not be exact, so keep that in mind. The glass release mechanism will only have power at the instant it is being released, not all the time. If the key will not "turn" in the rear lock, it could be a mechanical key cylinder problem (not electric). However, on my 1996 and 1999 the glass is popped by "pushing in" the key cylinder - not by turning the key. Turning the key locks and unlocks all the doors.

I looked at my diagrams for the 1999 rear glass release. This is what I found.
The relay you refer to is marked on the diagram as "lift glass relay". It is located under the hood on the drivers side where the hood meets the fender, above the wheel well in a rectagular black plastic box. There are multiple fuses and relays in this box. In this same blak box there is a 10amp fuse marked "MIR/LCK". This fuse feeds the power mirrors and the lift glass release. If this fuse is blown, the glass release will not work from any location and the power mirrors will not work. Do your mirrors work?

According to the 1999 diagram the relay is only for the dashboard button. There is a module which interfaces with the rear wiper to prevent you from opening the glass while the rear wiper is on. It also shows an interface with the parking brake. So the transmission must be in "park" and possibly, the parking brake may have to be engaged to pop the glass using the dash button.

The rear key switch in the door will work as long as the power doors are in the "unlock" position regardless of whether the under hood relay is good or bad. The fuse must be good though.

The button on the key-fob will probably work again when you resolve the vehicle problem.

Check your blazer and let us know what you found.

CORRECTION: the fuse is 6amp not 10 amp

[yeags]

Thanks for the reply. My 98 is a little different than your 99, however it is enough similar that your reply helped me figure out this problem- sort of...

My 98 liftgate opens the same way your 99 does - Botton on the dash, button on the remote, or by pushing in on the key cylinder on the back of the truck. I knew the actuator would only get power as the window was trying to get released, so I put my multi meter in the 2 pins on the actuators power supply and pressed the release button (and got nothing).

Here's what I found:

When I pushed either the button on the remote, or the button on the dash, I can hear the relay in the dash click, but I couldn't release the window. Pressing in on the key cylinder had no effect. Power mirrors have worked fine all along.

Since I could hear the relay click, I assumed that it was getting power and trying to send power to pop the window.

My "MIR/LKS" fuse is in the fusebox located inside the cabin (Drivers side between the dash and the door). This is a 5Amp fuse, and it looked good. I pulled that fuse and replaced it for giggles, and the liftgate started working on occasion. Not all the time- but I was able to find a pattern. If I manually open the whole rear gate, then close it, the window will pop once - every time. It will not pop again after I pop it that one time. It will pop from any of the 3 locations (dash, remote, rear cylinder), but will only do it once. If I open the rear gate, it will pop again - once.

I am now thinking that since the relay in getting power and sending power at times, the wiring from the relay to the back liftgate must be OK. Since I can only open it once, there must be something in that relay that does not work all the time, and my guess is that by opening the gate it somehow returns the relay to a state where it can once again pop the latch. Since I can hear the relay under the dash somewhere, I think I am going to find it and replace it this afternoon, and I will keep you posted.

Again, thanks for the reply.

[wirenut699]

Good to see you're making progress.

Did you mean that the old fuse was bad?

I'm wondering if the opening and closing of the whole rear gate is "resetting" the relay, or the slamming action is "correcting" a loose connection at the rear gate.

I'd like to know if opening and closing the gate without slamming / latching the gate also gets the glasss release working.

[yeags]

I changed the relay and it seems to have corrected the problem. I wasn't slamming the rear gate shut- just letting it close. As for the fuse... Your guess is as good as mine. The power locks and power mirrors all worked before the relay change, and they still do- only now the rear gate works too. Out of curiosity- I did a continuity check on the original fuse and it does test good. Who cares I guess- it is working.

Thanks for all your help.

[wirenut699]

Terrific

Till next time. Oh there will be!

[unclerumle]

Hey yeags ... I have the same problem as you with a 97 Blazer... Neither button (dash or hatch work), Where did you find the relay? I realize it's been ten years, but I hope you're still out there.