firenut Posted March 7, 2020 Share Posted March 7, 2020 I am having problems with my RPM gauge. The cable broke (tip that goes into the gauge) and I replaced it. That cable then broke and I replaced both the gauge and the cable again. Now again the cable broke in the same place. Can anyone give me some insight on the problem? I am at a loss... Quote Link to comment Share on other sites More sharing options...
mrgumby Posted March 7, 2020 Share Posted March 7, 2020 Did you replace both the cable housing and the drive cable or just the drive cable Maybe put a little lube in it also I’ve had the drive pin and adapter on the engine snap too. Since you replaced the tach head that’s all I can think of Quote Link to comment Share on other sites More sharing options...
Freightrain Posted March 7, 2020 Share Posted March 7, 2020 Did you replace the outer casing also? Or just the inner cable? The casing itself my have damage that is eating at the cable. If you replaced both pieces, that's good, but since it broke again with another gauge...that is a mystery. Does the cable have slack in it? Pulled tight around something? Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
firenut Posted March 8, 2020 Author Share Posted March 8, 2020 56 minutes ago, mrgumby said: Did you replace both the cable housing and the drive cable or just the drive cable Maybe put a little lube in it also I’ve had the drive pin and adapter on the engine snap too. Since you replaced the tach head that’s all I can think of Yep, replaced both, both times. I'm stuck..on what it could be and at $160 per cable from Mack... it's getting costly... Quote Link to comment Share on other sites More sharing options...
firenut Posted March 8, 2020 Author Share Posted March 8, 2020 57 minutes ago, Freightrain said: Did you replace the outer casing also? Or just the inner cable? The casing itself my have damage that is eating at the cable. If you replaced both pieces, that's good, but since it broke again with another gauge...that is a mystery. Does the cable have slack in it? Pulled tight around something? Yep, replaced both, both times. I have checked and see no place where it's "over taught". I am at a complete loss... 1 Quote Link to comment Share on other sites More sharing options...
Freightrain Posted March 8, 2020 Share Posted March 8, 2020 Two bad gauges? If it snapped the cable right at the gauge? Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
Phase 1 Posted March 8, 2020 Share Posted March 8, 2020 Turn the cable at the motor end while it is connected at the tach to see if it turns freely. Quote Link to comment Share on other sites More sharing options...
firenut Posted March 8, 2020 Author Share Posted March 8, 2020 10 minutes ago, Phase 1 said: Turn the cable at the motor end while it is connected at the tach to see if it turns freely. Thanks. I did forget to mention that I did that and it was free. strange thing is that it happend both times after the truck was running for about 20 minutes.. not immediately... Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted March 8, 2020 Share Posted March 8, 2020 when you say $160.00 from mack, means buying factory made for truck set up? reason I ask , is we always made up inner cable or outer housing. I agree with phase1 with manually turn cable . also disconnect from tach and start eng see how center cable runs. I've seen tangs break off in gauges bind up cables, believe you replaced gauge ,that would eliminate broken tang thought. electric drill on engine side with tach side slightly loose. Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted March 8, 2020 Share Posted March 8, 2020 20 min, was there a plastic insert in original housing for holding cable centered that was misplaced . what is broken ; cable itself or tang on end? Quote Link to comment Share on other sites More sharing options...
firenut Posted March 8, 2020 Author Share Posted March 8, 2020 11 hours ago, mechohaulic said: 20 min, was there a plastic insert in original housing for holding cable centered that was misplaced . what is broken ; cable itself or tang on end? It was the TAC end, not the drive end. That plastic piece is in good shape. Quote Link to comment Share on other sites More sharing options...
firenut Posted March 8, 2020 Author Share Posted March 8, 2020 11 hours ago, mechohaulic said: when you say $160.00 from mack, means buying factory made for truck set up? reason I ask , is we always made up inner cable or outer housing. I agree with phase1 with manually turn cable . also disconnect from tach and start eng see how center cable runs. I've seen tangs break off in gauges bind up cables, believe you replaced gauge ,that would eliminate broken tang thought. electric drill on engine side with tach side slightly loose. The cable is complete from Mack as the replacement. It comes with both pieces (inner and outer). I would certainly be happy if I could just replace the inner core.... it would seem cheaper. Quote Link to comment Share on other sites More sharing options...
Rob Posted March 8, 2020 Share Posted March 8, 2020 You really want a gentle or long sloping radius to the routing of those speedo and tach cables. I've seen several through the years broken off from the inner drive cable "whipping" internal to the outer jacket. Lube it up plenty even if brand new in the package till the oil runs out the other end as you pour. 1 Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
mechohaulic Posted March 8, 2020 Share Posted March 8, 2020 new cable/gauge only thing left is like Rob said , the radius. it would have to be a 90 degree to break that many so soon; doubt it's bent like that. what vehicle is it in ? been a while since working on fire trucks is there a rpm gauge on control panel ? I don't remember how panel gauge gets its source ; splitter box ? either way complete assy even a little long shouldn't break. how does the tach work for first 20 minute when running.: bounces, run smooth : other than angle only thing left would be wrong cable end . when you tighten cable to gauge it jams cable too tight? as earlier stated we made them back in the day. there was an assortment with different size ends. some tangs were longer. leave cable nut a little loose on gauge run it ?? Quote Link to comment Share on other sites More sharing options...
firenut Posted March 9, 2020 Author Share Posted March 9, 2020 9 hours ago, mechohaulic said: new cable/gauge only thing left is like Rob said , the radius. it would have to be a 90 degree to break that many so soon; doubt it's bent like that. what vehicle is it in ? been a while since working on fire trucks is there a rpm gauge on control panel ? I don't remember how panel gauge gets its source ; splitter box ? either way complete assy even a little long shouldn't break. how does the tach work for first 20 minute when running.: bounces, run smooth : other than angle only thing left would be wrong cable end . when you tighten cable to gauge it jams cable too tight? as earlier stated we made them back in the day. there was an assortment with different size ends. some tangs were longer. leave cable nut a little loose on gauge run it ?? The TAC cable runs directly from the top of the engine nearest the fan up through the cab floor into the guage. there is only one way to connect this cable, so I know its correct and I only hand tightened it on the guage end. You mentioned oil... The Mack store said this cable is ready to install the way it came. I did not put any oil in it. could that be the problem? I didn't notice any in the original cable either. Quote Link to comment Share on other sites More sharing options...
Rob Posted March 9, 2020 Share Posted March 9, 2020 Yes, it is ALWAYS a good idea to lube these cables prior to installation. One doesn't know the quality of the assembly lube, nor it's time on the shelf. Use a lubricant that is formulated for this purpose. When I ran the instrument shop the product used was marketed by the aftermarket division of the Stewart-Warner Corp. in a tube. It went in as a thin liquid, and solidified up as it dried. Much the same as good quality roller chain lubricant does which will work also. Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
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