I put in a 200A alt last year, can't remember when exactly but earlier in the week I noticed that my voltage was running low(<12V). I was able to limp her home and after that she needed a jump to start her up. I was confused since both the battery and the alt are not more then a year old but after getting it up to autozone and hooking it up to the machine it said I have a bad diode pattern and the alt needed to go. Of course the warrenty is up on it.... I found a local shop that can rebuild HO alts and I am going to drop it off tomorrow to see what they say.
While I have it torn apart and waiting for the alt to come back I am going to put on my cobra intake, 75mm MAF and 72mm TB that I ahve been waiting to put on. I wish I have the adjustable fuel pressure regulator that I need, but the money earmarked for that will proabably end up in the alt....
I heard that the HO alts tend to wear out faster then the stock ones(more current moving I guess?) but I also have to wonder if the underdrive pullies I had on it could have done some damage? The only thing that I noticed that could be bad was that the insulating boot that covers the ring terminal on the + wire between the alt and the battery looked hot and slightly melted. I am not sure if that is just due to engine heat or if it was from current draw? The rest of the wire looks good and it terminates at the platinum batter connector on the battery so I think it is just the heat from the engine that cause it but.........
Replies (8)
SQLThump on 06/18/2008 17:51:49
The only time I have seen an alt terminal melt or anything is when my dumb ass didn't properly tighten the bolts. They were a bit loose, which cost me my whole charging system, and eventually the whole car.
swez on 06/19/2008 04:18:21
Yep, sounds like the diode bridge failed. In today's ALT's, they use 3 phase diode arrays. If one set goes down, eventually the others will follow as they cannot take the extra heat and current.
If you have a good rebuilder in your area, ask if they can install a stronger diode bridge. (Takes more heat and current) Have him test the voltage regulator too. It may have taken a dump as well.
I doubt the under-sized pully did much harm. That just allows the ALT to spin faster at various engine RPM and allows more current output at low engine RPM. Have read that Competition/Racing ALT's are designed to spin up to 10,000 RPM w/o any problems. How long they will last at that level is hard to say. It depends on the bearings, pully tension, brushes and commutator balance.
Would think if they have the parts on hand, you'll be back on the road in a day or two and $150.00 at most for repairs?
Good luck,
Swez
ttocs on 06/19/2008 13:01:33
I found a place just down the road that rebuilds them. He ran a quick test on a piece of equipment that had to be 50 yrs old and said that it was the rectifier diodes going out. I asked if it was because of the UD pullies and he said that had nothing to do with it. He said that the high current models tend to run a little hot, especially under load and I am sure my amps are taxing it from time to time..... That usage along with the fact that we passed 110 in the past couple weeks must have done it in but he called back and said it was done and I was out $75.
This morning I started taking the top of the intake apart a little more(I am a complete motor newb). the screws holding the throttle position sensor had to be drilled out but that is the only part giving any problems. I have a couple more vacuume lines and a few more bolts before I have it out completely. I am going to let the sun go down and let the temp get a little closer to 100 before I try and finish up the intake tonight. Tomorrow I have to pick up the alt, the new screws and hopefully I will have it running tomorrow night to go cruising with my mustang club.
I have a guy in my club that wants to do a full custom system in a beautifull 1970 stang with a 429 cobra jet motor in it. He said he is willing to pay for it so hopefully I can recoup some of this and have some fun.
swez on 06/19/2008 16:00:50
Nice price on the ALT rebuild. Glad to hear it was only the diode pack and not deeper too. (Very good price) Did he use the same diodes or upgrade to a higher current diode/rectifier bridge?
The TPS you mentioned, is it malfuctioning or just needed to come off to work on the intake manifold? While you in there, inspect the vacuum lines closely. If they are brittle, cracked or flaking, replace them with fresh lines. It's a cheap fix and easy to do. If they are stuck hard to the vacuum mounts, use a razor knife to slit them for easy removal and replace as needed.
If needed, use self-tapping bolts and thread sealer, (Loctite) to keep them snug and they won't come loose later. Locktite makes some great products and easily found at most good AP stores and chains. If rust/corrosion is a problem, use Stainless Steel bolts. Just make sure you know the torque specs and use a good torque wrench.
Finally, have you considered a High Performance Chip set to change the fuel/air and timing advance parameters on the Momstang? This is not a cheap swap, but if you want better than OEM performance, this will help.
ttocs on 06/20/2008 10:52:50
The screws that hold the tps to the throttle body were stuck. I was removing it as I was putting on a larger TB and needed to switch it over ot the new one. I drilled out the screws and made a trip to ace to match up some screws.
I picked up the alt to day and I could actually see a difference in the rectifier as he put it down on the counter. He showed me the old one and pointed out that not only the 40A diodes in there, but the poor solder job done on them and the one that had melted. He said everything else looked good in side so he left it alone. IT appears that in my search to find the cheapest high output alt that I was successfull in more then one way......
I also put out an SOS on my mustangs clubs forum and found a guy that has the same year/make/model that has swapped the cobra intake a couple of times. It just so happens that he needs a box built and has no idea where to start so it appears that we will be friends shortly. He also happens to work at an autozone so he could be a good friend to have. Unfortunatly I will not get it back together in time to make the cruize tonight but.......
ttocs on 06/25/2008 17:29:38
damn its hot, 111 today..... The guy I found to help me with the motor is a 22 yr old. He got up at the crack of 11:30, had some breakfast/lunch and came right over at the peak of the heat at 1:30. We tore into it, and changed the plugs, plug wires, dist cap and rotor. Drained the radiator, removed some hoses, fuel rail, and are now at the point that we are ready to crack the lower inake off but he had to go to work and take off. He is supposed to get back to me tomorrow so we can finish it up. He has extra vacuum lines and o-rings for the fuel injectors so hopefully that is it.
Now after sweating my butt off, having broken nails and dirt under all the rest of them, a couple of busted knuckels I remember why I went into audio instead of motors. It was not that bad as it was good learning but.....
swez on 06/26/2008 22:23:27
Dang, that's pretty hot weather to do this kind of work in. Good thing you had a partner to stay in the game.
Some Go-Joe hand cleaner will help clean the gunk off your hands or diesel fuel works pretty well too, if you can stand the smell.
Yeah, working sockets and wrenches in tight spaces can be a pain on the knuckles. Especially if things are rusty and have not been removed in a long time. "Liquid Wrench" works pretty well on rusted/stuck bolts too. Just a few squirts and give it a few minutes to work, will usually do the trick.
Sounds like loads of fun,
Swez
ttocs on 06/30/2008 11:57:31
just finished up for the day at 4:30, only 109 today but there is no wind at all.....
We got the lower GT intake out and replaced, fuel rail and dist installed, replaced the plugs and wires, cap and rotor, thermostat.... We started to install the upper but ran into problems when the pipe that connects the EGR valve to the upper is too short. I installed a 3/8" phenolic spacer to keep the upper seperated from the lower for a cooler charge, as well as to lengthen the runners which adds some torque so the pipe is just that short now.
I am also hoping that I discovered the problem with the vacuum lines that has kept all of my ac and heat comming out of the windshield vent. Found a line that is broken that looks to be related. It will be cool to just have her back running, but I will be REALLY happy to see how much performace in adds, let alone just have my system playing again.
While I have it torn apart and waiting for the alt to come back I am going to put on my cobra intake, 75mm MAF and 72mm TB that I ahve been waiting to put on. I wish I have the adjustable fuel pressure regulator that I need, but the money earmarked for that will proabably end up in the alt....
I heard that the HO alts tend to wear out faster then the stock ones(more current moving I guess?) but I also have to wonder if the underdrive pullies I had on it could have done some damage? The only thing that I noticed that could be bad was that the insulating boot that covers the ring terminal on the + wire between the alt and the battery looked hot and slightly melted. I am not sure if that is just due to engine heat or if it was from current draw? The rest of the wire looks good and it terminates at the platinum batter connector on the battery so I think it is just the heat from the engine that cause it but.........
Replies (8)
SQLThump on 06/18/2008 17:51:49
The only time I have seen an alt terminal melt or anything is when my dumb ass didn't properly tighten the bolts. They were a bit loose, which cost me my whole charging system, and eventually the whole car.
swez on 06/19/2008 04:18:21
Yep, sounds like the diode bridge failed. In today's ALT's, they use 3 phase diode arrays. If one set goes down, eventually the others will follow as they cannot take the extra heat and current.
If you have a good rebuilder in your area, ask if they can install a stronger diode bridge. (Takes more heat and current) Have him test the voltage regulator too. It may have taken a dump as well.
I doubt the under-sized pully did much harm. That just allows the ALT to spin faster at various engine RPM and allows more current output at low engine RPM. Have read that Competition/Racing ALT's are designed to spin up to 10,000 RPM w/o any problems. How long they will last at that level is hard to say. It depends on the bearings, pully tension, brushes and commutator balance.
Would think if they have the parts on hand, you'll be back on the road in a day or two and $150.00 at most for repairs?
Good luck,
Swez
ttocs on 06/19/2008 13:01:33
I found a place just down the road that rebuilds them. He ran a quick test on a piece of equipment that had to be 50 yrs old and said that it was the rectifier diodes going out. I asked if it was because of the UD pullies and he said that had nothing to do with it. He said that the high current models tend to run a little hot, especially under load and I am sure my amps are taxing it from time to time..... That usage along with the fact that we passed 110 in the past couple weeks must have done it in but he called back and said it was done and I was out $75.
This morning I started taking the top of the intake apart a little more(I am a complete motor newb). the screws holding the throttle position sensor had to be drilled out but that is the only part giving any problems. I have a couple more vacuume lines and a few more bolts before I have it out completely. I am going to let the sun go down and let the temp get a little closer to 100 before I try and finish up the intake tonight. Tomorrow I have to pick up the alt, the new screws and hopefully I will have it running tomorrow night to go cruising with my mustang club.
I have a guy in my club that wants to do a full custom system in a beautifull 1970 stang with a 429 cobra jet motor in it. He said he is willing to pay for it so hopefully I can recoup some of this and have some fun.
swez on 06/19/2008 16:00:50
Nice price on the ALT rebuild. Glad to hear it was only the diode pack and not deeper too. (Very good price) Did he use the same diodes or upgrade to a higher current diode/rectifier bridge?
The TPS you mentioned, is it malfuctioning or just needed to come off to work on the intake manifold? While you in there, inspect the vacuum lines closely. If they are brittle, cracked or flaking, replace them with fresh lines. It's a cheap fix and easy to do. If they are stuck hard to the vacuum mounts, use a razor knife to slit them for easy removal and replace as needed.
If needed, use self-tapping bolts and thread sealer, (Loctite) to keep them snug and they won't come loose later. Locktite makes some great products and easily found at most good AP stores and chains. If rust/corrosion is a problem, use Stainless Steel bolts. Just make sure you know the torque specs and use a good torque wrench.
Finally, have you considered a High Performance Chip set to change the fuel/air and timing advance parameters on the Momstang? This is not a cheap swap, but if you want better than OEM performance, this will help.
ttocs on 06/20/2008 10:52:50
The screws that hold the tps to the throttle body were stuck. I was removing it as I was putting on a larger TB and needed to switch it over ot the new one. I drilled out the screws and made a trip to ace to match up some screws.
I picked up the alt to day and I could actually see a difference in the rectifier as he put it down on the counter. He showed me the old one and pointed out that not only the 40A diodes in there, but the poor solder job done on them and the one that had melted. He said everything else looked good in side so he left it alone. IT appears that in my search to find the cheapest high output alt that I was successfull in more then one way......
I also put out an SOS on my mustangs clubs forum and found a guy that has the same year/make/model that has swapped the cobra intake a couple of times. It just so happens that he needs a box built and has no idea where to start so it appears that we will be friends shortly. He also happens to work at an autozone so he could be a good friend to have. Unfortunatly I will not get it back together in time to make the cruize tonight but.......
ttocs on 06/25/2008 17:29:38
damn its hot, 111 today..... The guy I found to help me with the motor is a 22 yr old. He got up at the crack of 11:30, had some breakfast/lunch and came right over at the peak of the heat at 1:30. We tore into it, and changed the plugs, plug wires, dist cap and rotor. Drained the radiator, removed some hoses, fuel rail, and are now at the point that we are ready to crack the lower inake off but he had to go to work and take off. He is supposed to get back to me tomorrow so we can finish it up. He has extra vacuum lines and o-rings for the fuel injectors so hopefully that is it.
Now after sweating my butt off, having broken nails and dirt under all the rest of them, a couple of busted knuckels I remember why I went into audio instead of motors. It was not that bad as it was good learning but.....
swez on 06/26/2008 22:23:27
Dang, that's pretty hot weather to do this kind of work in. Good thing you had a partner to stay in the game.
Some Go-Joe hand cleaner will help clean the gunk off your hands or diesel fuel works pretty well too, if you can stand the smell.
Yeah, working sockets and wrenches in tight spaces can be a pain on the knuckles. Especially if things are rusty and have not been removed in a long time. "Liquid Wrench" works pretty well on rusted/stuck bolts too. Just a few squirts and give it a few minutes to work, will usually do the trick.
Sounds like loads of fun,
Swez
ttocs on 06/30/2008 11:57:31
just finished up for the day at 4:30, only 109 today but there is no wind at all.....
We got the lower GT intake out and replaced, fuel rail and dist installed, replaced the plugs and wires, cap and rotor, thermostat.... We started to install the upper but ran into problems when the pipe that connects the EGR valve to the upper is too short. I installed a 3/8" phenolic spacer to keep the upper seperated from the lower for a cooler charge, as well as to lengthen the runners which adds some torque so the pipe is just that short now.
I am also hoping that I discovered the problem with the vacuum lines that has kept all of my ac and heat comming out of the windshield vent. Found a line that is broken that looks to be related. It will be cool to just have her back running, but I will be REALLY happy to see how much performace in adds, let alone just have my system playing again.
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