ChesterChop Posted August 25, 2022 Share Posted August 25, 2022 I have an 1987 E9 400. The batteries on the passenger side are not changing. The ones on the driver's side are.My mechanic told me the alternator is working and the batteries are good but would have to dig into to figure out why. He said he didn't think it was a bad wire . He suggested getting a 12 volt starter and wiring it for that. Any ideas on what I can check? Quote Link to comment Share on other sites More sharing options...
ChesterChop Posted August 26, 2022 Author Share Posted August 26, 2022 Can anyone tell me where the parallel switch is located on this truck? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted August 26, 2022 Share Posted August 26, 2022 look under the right seat... 1 Quote Link to comment Share on other sites More sharing options...
ChesterChop Posted August 26, 2022 Author Share Posted August 26, 2022 Nothing electrical under the seat or under the cab in that spot. Someone said it was a module behind the alternator. My mechanic said he didn't think that was it. He hasn't worked on a lot of Mack's. Another guy told me the cables from the batteries will go to it first? I'll have to follow them tomorrow,I'm hauling today. I had a couple hours yesterday and was hoping it was something I could steal off my parts truck. Thanks Quote Link to comment Share on other sites More sharing options...
fjh Posted August 26, 2022 Share Posted August 26, 2022 57 minutes ago, ChesterChop said: Nothing electrical under the seat or under the cab in that spot. Someone said it was a module behind the alternator. My mechanic said he didn't think that was it. He hasn't worked on a lot of Mack's. Another guy told me the cables from the batteries will go to it first? I'll have to follow them tomorrow,I'm hauling today. I had a couple hours yesterday and was hoping it was something I could steal off my parts truck. Thanks Chester chop you need to change that compressor air filter , Just sayin! As for the charging issue check the big charge wire to the drivers side it had a joint in it right at the box that often caused charging issues! Solder it solid if it hasn't been already! 1 1 Quote Link to comment Share on other sites More sharing options...
ChesterChop Posted August 27, 2022 Author Share Posted August 27, 2022 I just serviced the truck last weekend and forgot about that one. I wasn't aware there was a filter there until someone on this page told me about it. I changed it out last service and it looked like it had been on there since 1989. I have one ordered. I'll have time tomorrow to climb around looking for the problem. I'll definitely check that wire, Thanks! Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted August 30, 2022 Share Posted August 30, 2022 Put a few of those filters in your shop.. save the part number in your book..... jojo 1 Quote Link to comment Share on other sites More sharing options...
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