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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / November 2005Is My Electrical Diagnosis Correct?
Hi, I have five questions (below). Both the blower motor and radiator fan for my '91 Chevy Cavalier 2.2 liter no longer work, even though I replaced both motors last week. The 25 amp AC/Heater fuse blows every time as soon as I turn the key to "run" with the heater on. I must have a short. After studying the wiring diagram, it seems the radiator fan and blower motor are on the same circuit. The wiring for this circuit goes as follows: Wire from Ignition Switch to 25 amp Heater/AC Fuse Then from this Fuse, wire to Splice A, with two wires coming out of this splice (wires 1 and 2 below): Splice A Wire 1: From Splice A to Heater Control Switch then to Blower Resistor then through the firewall then to Splice B: one wire to blower motor and the other to the blower relay Also, redundant ground from Blower Motor to Main Ground at Tranny Bolt Splice A Wire 2: From splice A through firewall then to Coolant Fan Relay then to Alternator input sensor [end] QUESTION 1: So does this mean the short must be between Splice A above and the ignition switch? QUESTION 2: If so, why does my alternator still work then, since that is also at the end of this same circuit?? I am at my wits end, as I was forced to purposely break my plastic center console in multiple places, just to access the blower motor switch. I was considering taking a Sawzall to it to get enough access. See, my shift stick knob would not come off, even though I pulled out the U-Pin. So I had no choice but to break the console into pieces to get to the blower switch. QUESTION 3: How do I get my shift stick know off if it is stuck on? Then, I was not able to perform the Chevy recommended diagnostic procedure with my DMM, since as soon as I turned the key to run, the fuse blew! And it is almost impossible to inspect the wiring, since the clusters are completely wrapped in electrical tape and very hard to access, even with the panels off, due to a metal support frame. It would take my hours just to remove the tape. And there is molten lava-like black gunk covering everything where my wire harness enters through the firewall. I thought is was dirt, but it feels too rubbery. It prevents me from seeing the wires at some points. QUESTION 4: What is this gunk? And now I have to remove the glove box and passenger side trim to access the blower resistor.! QUESTION 5: When will all this insanity end? All this just to find a short?! :) Thanks for any help! Julie > QUESTION 3: How do I get my shift stick know off if it is stuck on? Shift Stick KNOB! > QUESTION 3: How do I get my shift stick knob off if it is stuck on? Usually there is a horseshoe or staple shaped clip that holds the knob on. It usually goes on the front of the knob, where it is not easily seen.. If yours is of this ilk, just pry it out and the knob should come off. I will try to reconstruct your schematic and make a guess. >> QUESTION 3: How do I get my shift stick knob off if it is stuck on? > [quoted text clipped - 5 lines] > > I will try to reconstruct your schematic and make a guess. Thanks HLS. But I did take the U-clip off. And the knob was still stuck on the stick. Should I just yank on it with all my strength (without trying to hold the stick down)? Will I damage the tranny? Or will I yank the stick out fo the tranny if I did this? Julie > Thanks HLS. But I did take the U-clip off. And the knob was still stuck on > the stick. Should I just yank on it with all my strength (without trying to > hold the stick down)? Will I damage the tranny? Or will I yank the stick out > fo the tranny if I did this? > > Julie Although I am not familiar with this Cavalier application, GM normally just uses the U clip retainer, and the knob should come off. I havent noticed before that the park release button gets involved in holding the knob on, but you could try gently pulling and twisting while working that button. If you got really heavy handed, I guess you could always damage the shifter. But I think it is rather unlikely. I have a Chiltons or somesuch which applies to a number of GM cars, and will take a look a little later today to see if GM engineers have come up with some change in the setup. > > Thanks HLS. But I did take the U-clip off. And the knob was still stuck on > > the stick. Should I just yank on it with all my strength (without trying [quoted text clipped - 4 lines] > > > > Julie Re the stupid Chiltons, it was worthless. Sorry. >> > Thanks HLS. But I did take the U-clip off. And the knob was still stuck > on [quoted text clipped - 9 lines] > > Re the stupid Chiltons, it was worthless. Sorry. No problem HLS. Thanks for looking! I'll try wiggling around a little, but I can tell you it is stuck on pretty tight. Julie Just a thought for you. On the last heater blower I bought, the power plug was a 'universal' one that could have the negative in either of the two pin positions. If I had of gotten it wrong, I would blow the fuse instantly like you are doing. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id=2120343242 (More Off Road album links at bottom of the view page) > Hi, I have five questions (below). Both the blower motor and radiator fan > for my '91 Chevy Cavalier 2.2 liter no longer work, even though I replaced [quoted text clipped - 67 lines] > > Julie > Just a thought for you. > > On the last heater blower I bought, the power plug was a 'universal' one > that could have the negative in either of the two pin positions. If I > had of gotten it wrong, I would blow the fuse instantly like you are > doing. Hi Mike, thanks for the idea! My blower motor has only one terminal though, a positive one. The other negative terminal bolts on the motor housing (it is a redundant negative connection which you do not need for the blower motor to run), and I reused it on the new one. Oh, and btw, on the brand new AC Delco oil sender I installed last week, it came with some type of hardened pipe dope on the upper threads. I looked like tape, but it was some kind of dried gunk. I installed it, and my starting oil pressure is now up to 75 psi! It goes down after driving a while, but not as low, or at least not as fast. My horsepower also seems to have increased since I did this! It is easier to climb hills now. I only wish I knew the torque for this. I kept turning it tighter and tighter but did not want to go too far, in far of stripping the threads. Oh, and next weekend, I am pouring carburetor cleaner into my engine and will let it soak for 4 days. Then I will drain it and add oil, run it for 15 minutes, then drain it again. This will fix my low oil pressure! If not, I will try 20W-50 oil, although I am worried it will be too viscous for the winter. Julie > > Just a thought for you. > > [quoted text clipped - 25 lines] > > Julie I wouldn't jump up that high in oil viscosity. You say you use a 5W30 now I think it was, I would just go up to a 10W40 or even 10W30 for the winter. I use 10W30 in both of my engines year round and they see -30 and colder. And the blower does need the extra ground otherwise it will overload the harness or body ground. How about the new fan motor? Was the plug only one way on it too? I would start unplugging things. I would start with the heater motor and see if the fuse blows, then unplug the fan, then the fan sensor. Or do all 3 and see then start plugging things back in. The heater switch is mounted in plastic and is unlikely to short. The heater resistor is mounted in plastic I believe and hard to short also, but if it is in a metal box, then it could blow to a short. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id=2120343242 (More Off Road album links at bottom of the view page) >> > Just a thought for you. >> > [quoted text clipped - 37 lines] > winter. I use 10W30 in both of my engines year round and they see -30 > and colder. Ok, let me see how the carburetor cleaner works first. If I still have lower oil pressure, then I will go higher. I did use 10W-30 this summer though, and my pressure then was low. Right now, with my new sender unit installed and with 5W-30, my pressure is even higher than then! > And the blower does need the extra ground otherwise it will overload the > harness or body ground. Ok, good. > How about the new fan motor? Was the plug only one way on it too? Right, it can clip only one way. But I will recheck in ht morning, just to make 100% sure. Plus the old motor worked fine, both now and in the past, and clip was definitely correct then. > I would start unplugging things. I would start with the heater motor > and see if the fuse blows, then unplug the fan, then the fan sensor. > Or do all 3 and see then start plugging things back in. Ok, I will do this. Need to make sure I have enough fuses though! :) I will also try the fan relay as well, located between the fender and battery. I also know there are some fusible links involved with the fan motor, right above the starter, but I am having trouble knowing what these are supposed to look like or how to check them for a blown fuse, as they are wrapped in tape. > The heater switch is mounted in plastic and is unlikely to short. The > heater resistor is mounted in plastic I believe and hard to short also, > but if it is in a metal box, then it could blow to a short. Ok, at least I won't have to pull out my glove box then. So I guess my destruction of the center console trim to access the heater switch was all for naught. :) Julie Julie, I think something isn't right with your wiring diagram interpretation. You said: Splice A Wire 1: >From Splice A to Heater Control Switch then to Blower Resistor then through the firewall then to Splice B: one wire to blower motor and the other to the blower relay the problem here is that the blower RELAY isn't going to be downstream from the blower RESISTOR. What should be downstream from the blower resistor is the blower motor itself. Secondly, my advice to go about fixing this is this. You know that the circuit to the cooling fan is fine because when you turn the key on, with the blower motor turned off, the fuse doesen't blow. So you want to ignore that for the time being. Disconnect the blower relay and turn on the blower and see if the fuse blows. If it does not, then run jumpers from the relay socket to the relay COIL, and NOT to the CONTACTS. Turn on the blower again and see if the relay clicks on. If it does not blow then you know the short is in the large conductors from the relay to the blower motor. So in that case you can simply do this. Disconnect the feed from the harness to the blower motor, disconnect the feeds from the relay contacts to the harness. Run new wires from the downstream 20 amp fuse for the blower, to one of the relay contacts, then on through the firewall to the blower. If however the fuses does blow with the relay coil connected, then disconnect the output of the blower motor switch from the harness, and run a wire from that to the blower motor, and at the motor install an off the shelf relay. Feed the motor from a completely separate fused circuit you build. The blower will of course only run at high speed but this is a 14 year old car, who cares? Ted > Julie, > [quoted text clipped - 38 lines] > > Ted Her interpretation is right. At least my Jeep with it's GM blower fan is factory wired that way. The full 12 volt line goes to the resistor pack first, then piggybacks off it to the high speed or relay line. The full power plug at the resistor block has 2 wires crimped into it. I also have wired more than one heater fan direct. The switch on our Cherokee let the smoke out way back in the bush in the winter and we had to have defrost if nothing else. I fixed the switch and it lasted 2 years, then the heater just up and crapped out again on the first cold day. I used jumper wires to verify the motor worked and was ready to hot wire it again when I realized the power plug at the motor had a bad contact in it as I was pinning it for power with my multimeter. Going to go out today and cut that one line and solder it's own dedicated new plug into it or just jumper it with a soldered bridge. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id=2120343242 (More Off Road album links at bottom of the view page) Try squirting some oil in the key hole in the ignition switch. Don't ask me why but it cured an intermittenet problem with my heater fan and window wipers. That was after I had removed and inspected the wiper motor and removed the steering column cover and examined the ignition wiring. I'd also try some (penetrating) oil or WD-40 on the stick shift. > Try squirting some oil in the key hole in the ignition switch. > Don't ask me why but it cured an intermittenet problem with my heater fan [quoted text clipped - 3 lines] > > I'd also try some (penetrating) oil or WD-40 on the stick shift. Ok, I'll give these a try William. I know, one time I had an intermittent problem where the radio shut down while driving, and only restarting the car fixed this. The problem was traced to a faulty ignition switch, which I replaced. Julie |
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