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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Oct 2012 Posts: 307 'Bolter | | 'Bolter Joined: Oct 2012 Posts: 307 | I noticed my heater only runs when the truck is moving. It will not run when at idle. My wiring is most likely the problem, but I'm looking for suggestions. Thank you from a1958 Chevy Grumman.
1958 Chevy Grumman Olson step van
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | 1958 12v electrical system?
Does this happen when the lights are off?
What electrical devices are on? | | | | | Joined: Mar 2004 Posts: 6,212 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,212 | Is this a Fresh Air (Deluxe) or a Recirculating heater? What test methods have you used to confirm the fan only has voltage when the truck is moving? Mike B  | | | | | Joined: Mar 2011 Posts: 1,146 Shop Shark | | Shop Shark Joined: Mar 2011 Posts: 1,146 | This could be a rusty armature or worn brushes problem in the fan motor..
What happens is the armature gets rusty and the brushes can't make good contact with the armature.
With the truck moving, there is enough vibration for the brushes to make good contact with the armature.
To test this theory, turn on the fan and tap the fan motor with a hammer, see if fan motor starts to spin.
If it spins there could be two problems, the brushes are worn or the armature is rusty.
The fix is to ether replace the fan motor or sand down the armature with emery cloth to de-rust.
If brushes are worn you could replace brushes.
Note: Some fan motors are hard to take apart.
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | While spending the labor to take it apart, might be worthwhile to replace the motor. Most are available.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jun 2005 Posts: 1,001 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 1,001 | I have an Evans heater in my 55. Shows 6v on the case, so I disassembled it only to find out someone already put a 12v in it. Please easy to do. Just check your wiring.
Parts are available through Mill Supply.
Last edited by VEW; 02/18/2020 2:38 PM.
~ Victor 1941 3/4-Ton Pickup (in process). Read about it in the DITY Gallery1955 Grumman Kurbside "Doughboy" 235/3 on tree w/ OD 1957 3100 - moved on 1959 C4500 Short Bus "Magic Bus" - moved on 1959 G3800 1 Ton Dually "Chief" - moved on 1958 C4400 Viking "Thor" ~ moved on to fellow Bolter | | |
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