Next you will need to remove the glove compartment and maybe the ashtray. . First I had remove any of the parts that are connected to the basic plenum inside the cab where the core is installed. You have to first take off all the lower panels of the dash. In order to change a heater core in a 1995 or newer s10 pickup, you have to actually remove the entire dash, and lower the steering column. Remove the dash bolts it does not need to come all the way out.
This will allow you to raise the dash up a few inches. That is the big black plastic thing behind and underneath the glove compartment. Also while you are under the hood disconnect the heater hoses at the firewall where they hook to the core. I just asked the local dealership and they said that there is no heater conrol valve on a the blazer. I recently replaced the heater core in my 1985 Chev C-30 Silverado 1 Ton Pickup with air conditioning. If you have air it is a little harder.
Many people extend the life of their heater core by bypassing it during the summer months to avoid unnecessary corrosion or, or bypass it if it begins to leak. I have a Silverado with a 305, and here's what I did. Remove the screws that hold the cover in place to get at the core. There's just no way to get the new one in undamaged without doing this. You might as well buy new coolant while you're at it, too. I have done a couple of those, but it's been a while so I'll tell you what I remember. There is still considerable work to replace the core.
It's a black plastic box under the glove box, between the blower the round thing all the way in the bottom corner on the passenger side and … the ashtray area. You will need to remove the entire dash and still you will be swearing in sentences, I strongly suggest you let a shop do this, it will be worth it. Its not a fun job and I wouldn,t recomend it unless you are mechanicaly inclined and patient. There are about 8 screws. If you can't afford it and you are mechanicly inclined and have the time , give it a go.
It was hard to get to, but an extension was very helpful. S10- book time is about 10 hours. It may be necessary to get the housing loose from the firewall and lower it down a bit in order to diconnect everything. Under the hood you will have to take the remove the two hoses from the core tubes and then gently remove the core from under the dash. The screws that are at the back against the firewall are a pain to get at. You must remove the heater core housing.
Sorry I don't know what these gates are called but there is only one of each so you can readily identify them. One you have the housing in your hands you can remove the old core from the housing. Sounds simple but its not. A screw holds a clip that fastens the core in place. The heater core comes out from the inside. You pull out the glove box completely and remove the bolt that holds the dash to right side of the cab. Start by draining the coolant, disconnect dash board wiring harness from pcm behind kick panels, disconnect eye shaft, unbolt dashboard and remove dash.
It is also necessary to remove any thing that attaches the two halves of the plenum together. Look under the passenger side dash. There are about 5 or 6 nuts and there is one over by the fender that is tough to get. The heater plenum with the heater core inside can now be pulled away from the firewall far enough to reach behind and disconnect any remaining vacuum lines and electrical fittings. The hardest thing you can do? Not sure were this book gets its info! It took me 3 hrs and a little swearing and I did not remove the dash. Actually the job went easier than I expected.
I just replaced the heater core in my 95 S-10 and it was a pain in the butt. It took approximately 3 hours for removal, and approximately two hours to reinstall everything. Then it is necessary to remove the three nuts for the through studs that come from inside the cab and go through the firewall. Changing a heater core in a Chevy 1500. Normally, I remove the 4 screws on the top of the dash pad 7mm socket and the two screws 10mm socket on the bottom of the dash one by the door and one mid way acros … s and pull the dash off the firwall to make myself a little more room. Do everything in reverse to reinstall the new core. The plenum can now be removed from the vehicle.