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  #1  
Old 02-03-2008, 02:12 PM
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Default 98 Blazer Mileage & PRND21 **FIXED**

This problem has just gotten worse over time, all the gauges and instrument lights are fine, mileage and gear indicator lights use to work then it was intermittent, now they will not come on at all. Except when the temperature is close to freezing then if they work it is only until the truck warms up then they go off again. Sounds like a connector problem or a solder connection. I was wondering if any one else has had this problem? My inspection is duethis month and I need to fix.Besides the obvious, I am trying to find the common denominator between both mileage and gear indicator lights in the instrument cluster. I have removed the instrument cluster and resoldered almost all connections, but that did not work, could be a diode in the instrument cluster but there are no schematics. I am thinking it might be the transmission position switch for the PRND21 but I am not surewhat component sends singnal for the mileage. I do not have a life I have child support so taking it to the mechanic is out of the question, must fix it myself. Any suggestions would be helpful.

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Old 02-04-2008, 10:32 PM
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Default RE: 98 Blazer Mileage & PRND21 no show

Most likely you need a new gauge cluster. The circuit boards go bad, or the solders get weak, and they stop working. Just double check the fuses and make sure none are blown, if I remember correctly there is a separate fuse for the PRNDLand mileage. Do not replace the trans range switch thinking that will fix it, you will just be wasting your money there! Good Luck.
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  #3  
Old 02-05-2008, 02:47 AM
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Default RE: 98 Blazer Mileage & PRND21 no show

Deffinitly check your fuses first then let us know what comes from that so we can go further!!
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Old 02-05-2008, 08:22 PM
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Default RE: 98 Blazer Mileage & PRND21 no show

Last weekend I did take every fuse out of the fuse box, one at a time,near the drivers side doorand visually check to make sure they were not blown. After that I removed the instrument cluster and soldered about ten different connections that looked like cold solder,I didn't spend alot of time looking at all the connections mainly the ones in the areas of concern like the main connector for the wiring harness and the wires that connect the LED boards to the cluster board. I thought for sure that was my problem, put it all back together, nothing changed. Will be taking everything back apart this weekend and looking a little closer.Probably with a magnifying glass.
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Old 02-09-2008, 08:35 PM
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Default RE: 98 Blazer Mileage & PRND21 no show

Alright I fixed the problem and saved myself $350+ (counting the tickets I would have aquired from not being able to get my truck inspected, because I pass 8 donut shops to and from work, they are cop magnets for some reason) anyways I pulled the Instrument cluster again and took my time plus the use of a magnifying glass and found my problem. I was able to find wiring diagram for the connector and schematics for the Instrument Cluster and after checking each pin at the connector I determined everything was good up to that point, so I knew it was the cluster, sure enough there was a set of wires that went from the main board to the PRND321 board and the number 1 pin which was a ground plane for both the PRND321 and the Mileage board had a cold solder joint. resoldered that pin, took the cluster out to my truck and wa la it worked.

took some pictures to show everyone maybe save some one else some money.


Click the image to open in full size.


Click the image to open in full size.[/align]
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Old 02-09-2008, 08:54 PM
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Default RE: 98 Blazer Mileage & PRND21 no show

Thats awesome glad you got it fixed and saved yourself alot of money!!!
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Old 02-09-2008, 09:41 PM
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Default RE: 98 Blazer Mileage & PRND21 no show

Yup, that'll do it! Glad you got it fixed!!
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Old 02-10-2008, 02:22 AM
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Default RE: 98 Blazer Mileage & PRND21 no show

Good job! A lot of us would probably have given up and replaced the cluster.
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Old 11-30-2008, 10:25 PM
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Default RE: 98 Blazer Mileage & PRND21 **FIXED**

I am new to the Forum and had the same problem on my 1999 Blazer LS; the mileage and transmission selector display would go blank (started around 70,000 miles). After reading PCFIXIT's 2/10/08post I decided to see if I had the same problem. After removing the cluster I carefully pried off the bottom circuit board that contains the flourescent displays, then lifted up the display to expose the circuit board it is attached to. Sure enough, likePCFIXIT said the #1 lead from the display to the board had a bad solder joint. All the others were fine. Of course, I then checked the mileage display, same problem. Resoldered #1 lead hereas well. All is fine now.

Note that you have to clean the area around the pin real well for the solder to stick. I gave it a little shot of BrakeKleen and a little rubbing with the tip of a screwdriver to prepare the circuit board for fresh solder. Don't rub to much, you'll go right thru the printed circuit.
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Old 02-22-2009, 08:06 PM
 
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Default RE: 98 Blazer Mileage & PRND21 **FIXED**

hey guys i just joined because i am having the same problems as everyone else...the digital dash. I used to be able to push up on the bottom of the dash next to the parking brake release and I could get the odometer and speedometer to work. So I pulled the dash and now they work when I hit on the top of the dash. I have the dash out right this minute and I dont see anything that looks burnt or weak or broken or discolored or anything. The tach, rpm, oil, fuel, and batt. indicators all work fine as well as the high beam and parking brake lights etc. The only problem that I am having is with the odometer and speedometer. Please help in any way you can. Thanks.
Old 02-22-2009, 08:06 PM
 
 
 
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1994, 99, blazer, board, chevy, circuit, cluster, dash, diagram, display, instrument, milage, odometer, problems, wiring


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