I had to replace the heater core in my 1999 Chevrolet Blazer. I put the dash back together, but now I am having electrical problems.

First, the digial dash goes dark (mileage indicator and transmission indicator). It will light up when I first turn the key, but once I turn it over to start, it goes black.

Second, daytime running lights are not coming on. You can turn the lights on manually, but they should come on by themselves.

Third, the computer climate control doesn't work. I can't run A/C or heat.

Please help. I need my Blazer running.

I also have to two wires that do not have a home. One is on the driver side and one on the passenger side.

 

Sounds like you did not reconnect everything correctly when you put everything back together. Your only real choice is to dig back into it again. Make sure that all of the grounds are connected securely.

The dash going out could be caused by broken solders on the circuit board at the back of the cluster.

 

Took it back out, everything looks to be connected correctly. The digital dash comes on when I turn the power on, but once the car starts it goes out. I think the fuel gauge is out too, though the other gauges seem to be working.
The only grounding wire I know of is on the engine side of the firewall. Are there others?

 

There is a grounding wire that isn't attached that looks like it is coming from the battery. Does anyone have any idea where this goes?

Also, where are the grounding wires? I have located two so far that are attached to the engine side of the firewall. Am I missing any?

 

There should have been quite a few grounding lugs on the firewall inside.

 

Funny thing; removed fuse and the LED for transmission and mileage comes back on while its running, but the gauges go out. Put the fuse back in and the gauges come back on, but the LED for trans and mileage goes back out.

 

Sounds like pinched or crossed wires somewhere...

 

Is there a grounding wire in the cab somewhere? I didn't hook one up and I don't remember removing one.
Took it for a drive, the daytime running front lights came on for a bit, then back off. Windshield wipers don't work, front or rear. A/C and heater still don't work.

Could the main computer be causing this? It was dropped twice and was disconnected with the battery still connected. I know, i'm a beginner.

 

The connector on the passenger side, do you have the auxiliary power ports underneath the dash? As for grounding points, on the drivers side there's 3 behind behind the dash cluster/steering wheel. 2 studs on the firewall - one right above the other. On the passenger side there's 5. 3 in one harness, they go to a stud below the big square harness connector you showed in pictures 3 & 4. The 2 in the other harness go to a stud low on the firewall kind of centered on the drivers floorpan. Below where the open hole was when you had the heater box out. Ought to be harness hangers going on both of these studs too.

 

I don't remember removing these. I know I have a lot of screws left over, but I'll take the dash out again and see if I can find these ground wires.
Could this be what it is causing the problems?