Heater core replaced now it wont start

OK here is the problem,
I have a 99 CHavy Blazer with a 4.3L Vortex Engine. I just got done replacing the heater core in it. I put back together the dash and double/triple checked my electrical connections. so heres the problem:

1. Battery is reconnected and everything comes on. I double check the electrical (before i start the engine) to make sure the wipers work, radio, lights ect...this tells me that i have the electrical stuff in the dash hooked back up correctly.
2. I turn the key to the on position and everything lights up. the dash and all the warnings lights and sounds come on.
3. Turn the key and I hear a click from the engine (engine does not turn over) and POOF everything goes dead. NO LIGHTS OR ANYTHING
4. I disconnect the battery then reconnect it and everything comes back on.....then it repeats from step 2>

I did check all my fuses and they are all good!!???

ANYONE HAVE ANY IDEA WHATS GOING ON! WHY IS IT DYING WHEN I TURN THE KEY.???? HElP PLEASE,,,...!!!!

Are you sure the battery cables are clean and tight? This is usually a symptom of that type of problem, as the large load steals the current.

[Yup, double checked that and still the same problem. I think the computer might be reading a short or ground somewhere and shutting everything down on me? Not sure though.

Hey Max,

I have a 98 blazer and I am in the process of replacing my heater core. I have the dash removed and now I am trying to find all the nuts/bolts connecting the module to the dash still. I cant find them. My haynes manual says to take the one bolt out under the hood, then to take out the rest inside... I cant find them anywhere. Can you be of any help???

-Anthony

Check your voltage... if low you know the problem.

If you over torqued it when reconnecting it you may have broken something inside, I had that problem with my SS. Everything worked fine.... 12.6 volts as read with a Fluke volt meter. When I hit the key everything went black. I cleaned the connections, when I tried it again, everything went black again. My father-in-law (mechanic for over 50 years) suggested I swap out the battery he said that he had seen that before...it will run low current accessories but when it with a load it cuts out. I swapped it out and everything was fine. If you have another vehicle try swapping batteries.

Sounds like a bad battery connection. Mine battery is a little stripped out from an aftermarket terminal and it likes to cut out once every 6 months.

Sounds like a bad battery connection. Mine battery is a little stripped out from an aftermarket terminal and it likes to cut out once every 6 months.


OK guys found the problem....!!!!
The reason is was shutting down was because the computer was detecting a short somewhere. So as a safety feature it would shut everything down to prevent futher damage. So i figured OK what wire would be abnormal to the system and cause this.....OOOOOhhhhh my C.B. power wire. Come to find out I had accidently hooked it backed up to the auxillary power to the fuse box which was causing short to the system. I removed that and VOOOMMMM started right up. THanks guys for all the post to help me with this. This forum is great.

Anthony, I help you figure out the heater core. Give me your email address and I can email you step by step intructions.

Thanks

Hey Max,

I have a 98 blazer and I am in the process of replacing my heater core. I have the dash removed and now I am trying to find all the nuts/bolts connecting the module to the dash still. I cant find them. My haynes manual says to take the one bolt out under the hood, then to take out the rest inside... I cant find them anywhere. Can you be of any help???

-Anthony

Hey anthony,

Trust me i know your frustration, First of all the haynes manuel sucks. if you read the paragraph before the instructions it says, "for 1997 models and earlier"! funny huh? well not to us guys who own later years! hahah

OK so ill try my best here or you can email me apdcop1@yahoo.com and I can give you step by step instructions.

So you have the dash removed and now your trying to remove the black box that houses the heater core. Ok
First, DONT take out all the little screws that hold the upper and lower half of the housing together...dont need to and its a waste of time.
I have a 99 Blazer so hopefully your 98 is the same but on mine you have to go into the engine bay, near the heater core hoses in the center of the firewall (all by itself) you will see one protruding bolt the has a small nut on it, (10MM i think) take that out. Now on the left hand side of the heater hose (the bigger of the two) there is a bolt. This bolt is attached to that whole AC housing. it goes through the firewall and holds the inside on. take that out.

Now comes the fun one=
I am assuming you have AC in your truck, on top of the AC condenser unit you will see a little quote that says "cut here for service", take a knife and cut the rubber around the line of that electrical connector only. there will be 3 screws to remove that connector off the housing. take those out and remove the temp controller.
now if you look down that hole you will see a black bolt about half way down, you cant miss it its the only one there. you will need one of those swivel joint thingy's for your ratchet to get it out. once that is done you will notice that it should rock almost comepletly forward and out.

However there is a bolt at the bottom on the passenger footwell that needs to come out. then you will notice to small holes to either side of this bolt that has two bolts that come in from the oppisite side fo the firewall...well you cant get to those without taking the whole AC unit out.....so i just took a drummel tool and cut those tabs right off and whalla it comes right out. the whole unit. ( dont worry those tabs aren't required to keep that unit tight against the firewall. then you will see how to get to the heater core from there.

be careful not to cut or lean against those vacuum lines. I also found out its a good time to take a regular vacuum and clean out the ducts.

Hope this helps you out.

Max