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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / October 2005Help!! Car blows fuses. Can I use a slow blow fuse???
My '94 Bonneville has blown the fuse to the air pump for the air shocks several dozen times over the last 8 years. Two dealers, a different pump, and and $800 later it still blows fuses. The only component on the fuse is the pump and the Chevy dealer contends I need to try a third pump. I'm not convinced. I wondered if trying a slow blow fuse (if they exist) might help. The fuses I have been using are ATO 20A - small with square ended terminals. Anyone know if they make slowblow fuses like that and where to get them??? I'm definitely about out of options. At first we thought there might be a short somewhere, but never found any. The mechanic even removed the dashboard to rewire and refuse the components (I think he said 3) that were on the original circuit. Now, the pump is on a circuit by itself. I have watched the pump run and it sounds good. Seems to run about 10 seconds when it does run and then shuts off without blowing the fuse. I can't tell exactly when the fuse blows, but of course the ride soon suffers. Any help would be GREATLY appreciated. I have an appointment with ANOTHER mechanic in about 10 days, but hope maybe to try a different type of fuse first. Love the car otherwise, but this problem has been a big pain. There MUST be an answer!!! Bob Henninger > My '94 Bonneville has blown the fuse to the air pump for the air > shocks several dozen times over the last 8 years. Two dealers, a [quoted text clipped - 21 lines] > > Bob Henninger I don't know anything about your car or the amps required by the pump. You should check the requirements of that pump. In any case, I don't see what it would hurt to go with a bigger fuse. You have the circuit isolated anyway. If it's a 15A fuse not it should take a 20A with no bad consequences. Most serious shorts vasstly overpower the fuse anyway so you will still be protected. If it were me I'd reach into my junk box and pull out a resettable fuse at the required amperage and try that until I had it figured out. For research purposes you could wire in a test lamp and watch it on your dash for the event that precedes the blowout. Since this has happened to more than one pump and the circuit is newly wired, I suspect it's under fused. > My '94 Bonneville has blown the fuse to the air pump for the air > shocks several dozen times over the last 8 years. Two dealers, a [quoted text clipped - 21 lines] > > Bob Henninger Put an equal rating slo-blo in it and see what happens. The difficulty may lie in finding one in the "blade" format - I'm really not sure if there are slo-blo blade style fuses available, since I've never had a reason to look for them. You may need to go to a fuse adapter rig so you can replace the blade style with the tube style. Either way, if it's blowing because the pump is overdrawing as it loads up, it'll likely blow again, but should take slightly longer to do so, perhaps allowing the pump to "finish" and shut itself off so things cool back to normal before getting hot enough to actually fry the fuse. Another thing I'd be looking at would be the cut-out switch, or any controlling sensors that are involved with turning the pump on and off. This on the suspicion that maybe the pump isn't being told to turn off, and it can only handle pumping against <pick a number> PSI of backpressure before overloading and blowing the fuse. Could indicate a sensor that needs tweaking/replacing, a need for a new switch, or both. If it's having to run so long/often that it cooks off fuses, it's also possible that you've got something leaking in the system. If that's the case, finding and fixing the leak would likely fix the fuse, albeit indirectly.  SignatureDon Bruder - dakidd@sonic.net - New Email policy in effect as of Feb. 21, 2004. Short form: I'm trashing EVERY E-mail that doesn't contain a password in the subject unless it comes from a "whitelisted" (pre-approved by me) address. See <http://www.sonic.net/~dakidd/main/contact.html> for full details. i would be looking at the wires for a resistence and would bet the wire is getting warm > > My '94 Bonneville has blown the fuse to the air pump for the air > > shocks several dozen times over the last 8 years. Two dealers, a [quoted text clipped - 49 lines] > subject unless it comes from a "whitelisted" (pre-approved by me) address. > See <http://www.sonic.net/~dakidd/main/contact.html> for full details. >My '94 Bonneville has blown the fuse to the air pump for the air >shocks several dozen times over the last 8 years. ... >At first we thought there might be a short somewhere, but never found >any. ... Not the same thing, but my Cavalier would intermittently blow its fuel pump fuse. The Cav pump relay is on the inner fender, so the wire is routed through the engine harness. The jacket on the harness was open enough so that the wire in question rubbed on a bracket. The insulation eventually wore through, and whenever the wire made contact with the metal, poof. Before I found that, I did try a larger fuse. It still blew, of course. I think is would be perfectly safe for you to do that. But, in the end, I think you'll find that it's a short. Good luck, George > I wondered if trying a slow blow fuse (if they exist) might help. The > fuses I have been using are ATO 20A - small with square ended > terminals. > Anyone know if they make slowblow fuses like that and where to get > them??? How about a circuit breaker that plugs into the same ATO slot? Wrecking yard cars are full of them. Go grab a pocketful. How much does a new air pump cost, and how hard is it to install compared to a fuse? I'd measure the current draw and the voltage at the pump's terminals since electric pumps often draw more current than normal when the pump mechanism wears or when the motor doesn't receive full voltage. Be sure to measure the voltage at the pump's terminals, not the terminals of the connector that plugs into them. Compare this to the voltage at the battery terminals; it should be within 1/2 V. While you're at it, unplug and clean all the connections (don't sand them -- can remove protective plating), pry any press-on terminals so they grip better, and coat terminals with silicone grease (Radio Shack's transistor heatsink grease, automotive dielectric grease, or computer CPU heatsink grease, provided the latter doesn't contain silver). Apply the grease before reassembly so it seals out water better. The grease will not impede flow of current since the metal pierces its film. If for some strange reason GM uses the chassis as the negative connection for the pump, clean that connection too, and consider running an extra ground wire (#10-12 is fine). Thanks very much to all of you for your great ideas! I haven't had a chance yet to try any of them myself. The car goes into the shop this afternoon. I will print all of your responses and give them to the mechanic. Will post the final outcome here, hopefully later this week. BTW, just returned from a 400 mile trip with no blown fuses. Sheesh. Thank you again for taking the time to help. Bob Henninger >My '94 Bonneville has blown the fuse to the air pump for the air >shocks several dozen times over the last 8 years. Two dealers, a [quoted text clipped - 21 lines] > >Bob Henninger Have you installed an ammeter across the fuse plug and actually viewed the amperage drawn? On my old Saturn one circuit had the electric window motors in the same circuit as some the wipers (?). If the wipers were on and I happened to hit a window switch the fuse would blow. Turns out there was a memo to the dealer that the fuse value was too low for that circuit. It was doubled, as I recall, and all blown fuse problems went away. The ammeter showed the circuit as just about maxed, but when the wiper washer was activated it went over. Slow-Blo fuse didn't matter much. It was too low to begin with if all accessories were switched on in that circuit. Mack >Have you installed an ammeter across the fuse plug and actually viewed the >amperage drawn? >On my old Saturn one circuit had the electric window motors in the same >circuit as some the wipers (?). If the wipers were on and I happened to hit [quoted text clipped - 4 lines] >over. Slow-Blo fuse didn't matter much. It was too low to begin with if >all accessories were switched on in that circuit. Slow-blo fuses aren't that slow. Using such a fuse would only matter if you were somehow able to finish raising your windows in under a half second. |
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