95 Blazer accurate electrical schematic?
Chaindrive
12-17-2005, 03:10 AM
I'm trying to locate an accurate electrical schematic for this vehicle. I've found two different ones and they conflict a bit (Chiltons vs. "online source").
I am having electrical problems which have been presenting themselves in several various and seemingly random ways. Fuel pump, vcm, no spark, blowing ignition fuse for awhile (this quit after replacing vcm; car worked for a few weeks but then no spark), dead batteries... Replacing everything is getting expensive and producing no results.
In my latest diagnostic attempt I systematically disconnected: VCM, battery, crank pos sensor; coil module, coil, HVS.
Using a portable 12v jumpstart battery pack, I connected the negative lead to my negative battery cable. I then ran a small positive jumper wire to the fuse block to the connection for the ignition ecm circuit (the fuse that had been blowing once upon a time) powering ONLY that circuit.
The idea was to test for current using a simple probe tester at each of the components supplied by that circuit to provide ignition. The insulation for those wires showed signs of once having been hot, but no readily visible breeches in the insulation or breaks in the wiring. All testing was done with key both on and off since this circuit has two wires and one of the diagrams shows one of them going to the ignition switch while the other does not... (Hence my need for a definitive schematic)
Positive current at connector? >>>
Fuel injector: OK
Crank position sensor: OK
VCM : OK (at the proper terminal according to one source)
Coil module: NOTHING
Coil: NOTHING (one manual shows this is powered by a different circuit and the other manual shows it should be powered by this one)
HVS: NOTHING (again, the two manuals/diagrams disagree on how this is powered)
I also tested for grounds and shorts:>> Seems OK
While testing for possible shorts to ground (Negative power lead connected to negative battery cable; test probe ground lead now connected to positive power source lead which will cause tester to light when probe contacts ground) I discovered what appears to be a major short circuit at the main junction box on the driver side fender where several fusible links (all in apparent good condition) are connected.
Disconnecting them and testing each individually showed two with a very strong ground and one with a very weak ground. This/these short(s) was transferred to all of the wires at that junction block, of course. No wonder my batteries were being killed! I also found a very weak ground at my positive battery cable.
Finding accurate info on the function of each of the three fusible link wires in question is proving very difficult, but it would appear that the common thread to all of these is they all connect directly or indirectly with the ignition switch, as does the the ignition circuit which has no spark.
I think: "Ah-Ha!! I found the problem: the ignition switch itself."
Disconnecting the ignition switch harness from the junction block beneath the dash and repeating the testing now shows only two fusible link wires with very brief (2 second) and very weak grounds which then end (like they are in a circuit with a timer like what powers the fuel pump). There is no longer any indication of ground at my positive battery cable anymore either.
Since the brief and weak ground now being shown by the two positive fusible link wires is so regular and timed and it stops after 2 seconds; I am inclined to disregard them as a normal effect of a timed circuit and continue with the ignition switch being my prime suspect.
If I can find the right torx socket to remove the doggone switch, I will spring for another $140 and replace it. Any ideas where to get one? My buddy the Snap-On dealer died a year ago, so I don't have a "weekend specialty-tool connection" anymore.
Does anyone have any other suggestions? Does anyone think I am wrong about the ignition switch?
Incidently, the lead to energize the fuel pump also shows a very strong ground. Should it?
Any help will be greatly appreciated. I have searched the forum and old threads exhaustively, and i see the ignition switch in this 95 Blazer is an old culprit in many problems.
Thank you and Merry Christmas! Scott
I am having electrical problems which have been presenting themselves in several various and seemingly random ways. Fuel pump, vcm, no spark, blowing ignition fuse for awhile (this quit after replacing vcm; car worked for a few weeks but then no spark), dead batteries... Replacing everything is getting expensive and producing no results.
In my latest diagnostic attempt I systematically disconnected: VCM, battery, crank pos sensor; coil module, coil, HVS.
Using a portable 12v jumpstart battery pack, I connected the negative lead to my negative battery cable. I then ran a small positive jumper wire to the fuse block to the connection for the ignition ecm circuit (the fuse that had been blowing once upon a time) powering ONLY that circuit.
The idea was to test for current using a simple probe tester at each of the components supplied by that circuit to provide ignition. The insulation for those wires showed signs of once having been hot, but no readily visible breeches in the insulation or breaks in the wiring. All testing was done with key both on and off since this circuit has two wires and one of the diagrams shows one of them going to the ignition switch while the other does not... (Hence my need for a definitive schematic)
Positive current at connector? >>>
Fuel injector: OK
Crank position sensor: OK
VCM : OK (at the proper terminal according to one source)
Coil module: NOTHING
Coil: NOTHING (one manual shows this is powered by a different circuit and the other manual shows it should be powered by this one)
HVS: NOTHING (again, the two manuals/diagrams disagree on how this is powered)
I also tested for grounds and shorts:>> Seems OK
While testing for possible shorts to ground (Negative power lead connected to negative battery cable; test probe ground lead now connected to positive power source lead which will cause tester to light when probe contacts ground) I discovered what appears to be a major short circuit at the main junction box on the driver side fender where several fusible links (all in apparent good condition) are connected.
Disconnecting them and testing each individually showed two with a very strong ground and one with a very weak ground. This/these short(s) was transferred to all of the wires at that junction block, of course. No wonder my batteries were being killed! I also found a very weak ground at my positive battery cable.
Finding accurate info on the function of each of the three fusible link wires in question is proving very difficult, but it would appear that the common thread to all of these is they all connect directly or indirectly with the ignition switch, as does the the ignition circuit which has no spark.
I think: "Ah-Ha!! I found the problem: the ignition switch itself."
Disconnecting the ignition switch harness from the junction block beneath the dash and repeating the testing now shows only two fusible link wires with very brief (2 second) and very weak grounds which then end (like they are in a circuit with a timer like what powers the fuel pump). There is no longer any indication of ground at my positive battery cable anymore either.
Since the brief and weak ground now being shown by the two positive fusible link wires is so regular and timed and it stops after 2 seconds; I am inclined to disregard them as a normal effect of a timed circuit and continue with the ignition switch being my prime suspect.
If I can find the right torx socket to remove the doggone switch, I will spring for another $140 and replace it. Any ideas where to get one? My buddy the Snap-On dealer died a year ago, so I don't have a "weekend specialty-tool connection" anymore.
Does anyone have any other suggestions? Does anyone think I am wrong about the ignition switch?
Incidently, the lead to energize the fuel pump also shows a very strong ground. Should it?
Any help will be greatly appreciated. I have searched the forum and old threads exhaustively, and i see the ignition switch in this 95 Blazer is an old culprit in many problems.
Thank you and Merry Christmas! Scott
Southern Comfort
12-17-2005, 08:21 AM
Hey Scott, Sears is a pretty good source for torque bit.
Here is a link where you can get a cd for the specific vehicle. I get all mine from there and they are the best I've found. The cost is 25 dollars and no shipping. However, I do have the schematics for a 1999 S10. I'm not sure if it is exactly like yours but should be close enough to troubleshoot your car. Your are welcome to it if you want. it won't cost you a thing but your time to e-mail me and tell me you want it. I'll be happy to send it to you.
Southern
http://www.autorepairmanualcd.com/index.php
Here is a link where you can get a cd for the specific vehicle. I get all mine from there and they are the best I've found. The cost is 25 dollars and no shipping. However, I do have the schematics for a 1999 S10. I'm not sure if it is exactly like yours but should be close enough to troubleshoot your car. Your are welcome to it if you want. it won't cost you a thing but your time to e-mail me and tell me you want it. I'll be happy to send it to you.
Southern
http://www.autorepairmanualcd.com/index.php
rlith
12-17-2005, 08:49 AM
You also have to be aware, there are 2 different versions of the 95... The 1st is ODBI (ECM under the dash) and ODBII (1st revision, ECM on the coolant recovery tank)... Be aware of which diagram you're using.. You should consider www.alldata.com which has both diagrams. I tend to agree based on your existing tests and your symptoms, it's your ignition switch. You can pick up the torx bit at any autoparts stores.
Southern Comfort
12-17-2005, 09:20 AM
You also have to be aware, there are 2 different versions of the 95... The 1st is ODBI (ECM under the dash) and ODBII (1st revision, ECM on the coolant recovery tank)... Be aware of which diagram you're using.. You should consider www.alldata.com which has both diagrams. I tend to agree based on your existing tests and your symptoms, it's your ignition switch. You can pick up the torx bit at any autoparts stores.
Thanks rlith, Chain drive is the one needing the help with the wiring diagram. I was just trying to lead him in a new direction for the schematic for the year of his blazer. I have to agree with all the people , who have said, this is the best forum I've ever seen. You guys are very helpful and very knowledgeable about these vehicles. Thanks man.
Southern. I do have a complete cd on every thing about my 1999 ZR2 S10 4x4. All the wiring diagrams and so on.
Thanks rlith, Chain drive is the one needing the help with the wiring diagram. I was just trying to lead him in a new direction for the schematic for the year of his blazer. I have to agree with all the people , who have said, this is the best forum I've ever seen. You guys are very helpful and very knowledgeable about these vehicles. Thanks man.
Southern. I do have a complete cd on every thing about my 1999 ZR2 S10 4x4. All the wiring diagrams and so on.
Chaindrive
12-17-2005, 12:39 PM
The alldata.com link is the online source I used which conflicts a little with my Chilton's manual. The autorepairmanualcd.com link is one I used about 9 days ago to order that cd for the Blazer, but it has not arrived yet. Kind of slow service I guess.
This Blazer has the OBDII configuration with the passenger-side fenderwell mounted VCM-A and a II style underdash diagnostic connector. Interestingly (thank you GM, always so helpful) the emissions label says it is an OBDI vehicle... This caused a great deal of confusion once, but it is definitely the later-year model '95 with the W-series Vortec 4.3 . Thanks for the second vote for the ignition switch, too, rlith, it makes me feel a little better about plopping that additional cash down. I have been chasing my tail and buying unecessary parts for this vehicle for quite awhile, but this time it feels justified logically.
Southern, I want to thank you for the extremely generous offer of that cd. That is very kind of you. If the one I ordered does not show up soon, I may take you up on that.
I'm off to Sears to find a torx socket. According to the ignition switch replacement guide i found here, I need a T3, but a T4 might work? Seems T3's are non-existant as I call around...
I am being asked by AutoZone and Napa whether the vehicle has an airbag or not since there are two different switches for that vehicle. Ours has one. Advanced Auto has no idea what the difference is, but also shows two switches, so advised ordering both... All of them are outrageously expensive ($145 to $175), so they must be made in Mexico (the GM modern rule of thumb being: The more inferior the component, and the cheaper it is to have made elsewhere and import, the more it costs the consumer and the more it fails [the notorious gm-trademark leaky oil cooler and filter lines being a prime example. If the EPA really cared about groundwater pollution they would make gm recall about 50 million vehicles equipped with those leaky lines]... :shakehead ). OK, I'm done ranting for now and mentally prepared for the sticker-shock... :screwy:
This Blazer has the OBDII configuration with the passenger-side fenderwell mounted VCM-A and a II style underdash diagnostic connector. Interestingly (thank you GM, always so helpful) the emissions label says it is an OBDI vehicle... This caused a great deal of confusion once, but it is definitely the later-year model '95 with the W-series Vortec 4.3 . Thanks for the second vote for the ignition switch, too, rlith, it makes me feel a little better about plopping that additional cash down. I have been chasing my tail and buying unecessary parts for this vehicle for quite awhile, but this time it feels justified logically.
Southern, I want to thank you for the extremely generous offer of that cd. That is very kind of you. If the one I ordered does not show up soon, I may take you up on that.
I'm off to Sears to find a torx socket. According to the ignition switch replacement guide i found here, I need a T3, but a T4 might work? Seems T3's are non-existant as I call around...
I am being asked by AutoZone and Napa whether the vehicle has an airbag or not since there are two different switches for that vehicle. Ours has one. Advanced Auto has no idea what the difference is, but also shows two switches, so advised ordering both... All of them are outrageously expensive ($145 to $175), so they must be made in Mexico (the GM modern rule of thumb being: The more inferior the component, and the cheaper it is to have made elsewhere and import, the more it costs the consumer and the more it fails [the notorious gm-trademark leaky oil cooler and filter lines being a prime example. If the EPA really cared about groundwater pollution they would make gm recall about 50 million vehicles equipped with those leaky lines]... :shakehead ). OK, I'm done ranting for now and mentally prepared for the sticker-shock... :screwy:
MT-2500
12-18-2005, 01:08 PM
http://members.troublecodes.net/crunch/95b.pdf
Sometimes you can get some wiring on auto zone site.
Also the all data DIY repair info sub is one of the best deals.
If the sub does not have what you need contact them and they will help you out.
Link below MT
http://www.alldata.com/products/diy/index.html
Sometimes you can get some wiring on auto zone site.
Also the all data DIY repair info sub is one of the best deals.
If the sub does not have what you need contact them and they will help you out.
Link below MT
http://www.alldata.com/products/diy/index.html
Southern Comfort
12-18-2005, 01:35 PM
http://members.troublecodes.net/crunch/95b.pdf
Sometimes you can get some wiring on auto zone site.
Also the all data DIY repair info sub is one of the best deals.
If the sub does not have what you need contact them and they will help you out.
Link below MT
http://www.alldata.com/products/diy/index.html
I appreciate all the help. I'll look at the url's and give it a shot. I'm in the middle of dropping my tranny to rebuild it. Thanks for your help.
Southern
Sometimes you can get some wiring on auto zone site.
Also the all data DIY repair info sub is one of the best deals.
If the sub does not have what you need contact them and they will help you out.
Link below MT
http://www.alldata.com/products/diy/index.html
I appreciate all the help. I'll look at the url's and give it a shot. I'm in the middle of dropping my tranny to rebuild it. Thanks for your help.
Southern
MT-2500
12-18-2005, 05:55 PM
You are welcome
And if rebuilding the trans yourself the all data diy would be a big help with it to.
On the pdf link copy it off because the site act up at times or goes off.
On the trans be sure you flush or clean the trans/rad oil cooler good.
Good luck with it.
And let us know how it goes.
MT
And if rebuilding the trans yourself the all data diy would be a big help with it to.
On the pdf link copy it off because the site act up at times or goes off.
On the trans be sure you flush or clean the trans/rad oil cooler good.
Good luck with it.
And let us know how it goes.
MT
Southern Comfort
12-21-2005, 10:09 AM
You are welcome
And if rebuilding the trans yourself the all data diy would be a big help with it to.
On the pdf link copy it off because the site act up at times or goes off.
On the trans be sure you flush or clean the trans/rad oil cooler good.
Good luck with it.
And let us know how it goes.
MT
Hey MT,
I appreciate your advice about the alldata website. It is an interesting site. I have my transmission out and disassembled. I found the sun shell reaction was broken. I have rebuilt my transmission completely and hope to put it back in today, weather permitting of course. The reason I am writing this is, while removing my transmission from my ZR2 4x4, I noticed the connector going to my transfer case was loose. The 8mm/ 5/16 bolt was loose. I have been having the same problem that many of the people in the forum have been complaining about their 2hi/4hi/4lo light blinking and not staying on. I think this could have been the reason the light doesn’t come on and stay on. I loose connection on the connector going to the transfer case. I won’t know for sure, until I put the tranny back in. But, I’ve been working in electronics for 30 + years and have seen my share of cold soldier joints (loose connections). I just wondered if you think it’s is a possible problem, seeing how you are a mechanic for all those years. If nothing else, it’s worth the time to tighten the bolt to see if that fixes the problem. I’ll keep you posted on my progress. I don’t know if I should post it or not. However, once I get the time, I’ll post it as something worth while to check. If you have the time, I’d appreciate it if you would post it. People in the forum tend to respond to your post.
Thanks Man
Southern Comfort
P.S., If you ever have any problems about computer or such, feel free to e-mail me. I an A+ certified and have worked on computers for 20 years.
And if rebuilding the trans yourself the all data diy would be a big help with it to.
On the pdf link copy it off because the site act up at times or goes off.
On the trans be sure you flush or clean the trans/rad oil cooler good.
Good luck with it.
And let us know how it goes.
MT
Hey MT,
I appreciate your advice about the alldata website. It is an interesting site. I have my transmission out and disassembled. I found the sun shell reaction was broken. I have rebuilt my transmission completely and hope to put it back in today, weather permitting of course. The reason I am writing this is, while removing my transmission from my ZR2 4x4, I noticed the connector going to my transfer case was loose. The 8mm/ 5/16 bolt was loose. I have been having the same problem that many of the people in the forum have been complaining about their 2hi/4hi/4lo light blinking and not staying on. I think this could have been the reason the light doesn’t come on and stay on. I loose connection on the connector going to the transfer case. I won’t know for sure, until I put the tranny back in. But, I’ve been working in electronics for 30 + years and have seen my share of cold soldier joints (loose connections). I just wondered if you think it’s is a possible problem, seeing how you are a mechanic for all those years. If nothing else, it’s worth the time to tighten the bolt to see if that fixes the problem. I’ll keep you posted on my progress. I don’t know if I should post it or not. However, once I get the time, I’ll post it as something worth while to check. If you have the time, I’d appreciate it if you would post it. People in the forum tend to respond to your post.
Thanks Man
Southern Comfort
P.S., If you ever have any problems about computer or such, feel free to e-mail me. I an A+ certified and have worked on computers for 20 years.
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