the 91 in my sig has an issue with the heater/brakes

if i have the heater on at any setting driving along the volt idiot gauge reads o nthe high end of "normal" if im coming up to a stop sign or slowing down as soon as i hit about 20MPH and i am on the brakes the volt gauge drops immediately to the middle of "normal" and continues to slowly drop till i come to a full stop at the low end or "normal" then it stays there. if i put it in park and let off the brake it immediately jumps back to the high end, if i hold the brake in drive it jumps from the low end to the high end as soon as i rev it up a bit with the brake still on.

the voltage drop gets lower as the heater setting is lower, if i shut the heater off it does not do this?

i have never EVER seen of heard of anything like this before...not a huge deal truck will be parked for half a year in about 2 weeks so its not matter but i just wanted to see if anyone else has experienced this or knows the fix?

 

Make sure that the battery connections are clean and tight. Check that where the ground wires from the battery bolt to the engine and to the body are clean and tight. Check the ends of the main battery wires, under the insulation for any signs of burning or corrosion. If all that checks out good then it may be worth getting a load check done on the battery.

 

i just replaced the pos battery cable a few months ago, from the battery to the switch any way...it just started doing this not too long ago and i looked at that stuff quick a few days ago and it all looked fine, maybe ill have to throw our load tester at it and see what happens

 

took a better look at the cables today when the truck decided not to start and found either corroded or loose wires in the neg battery cable near the battery, wiggle the end and it was tight with the post but it move a little and the truck fired right up, so i guess that will be the place to start when i get er movin next spring...the cable looks fine and is tight so there must be corrosion or something hidden inside the insulation

 

when you say you turn the heater up you mean you turn the heater blower up? if so then i think that you need to start there, wiring, relay or resistor or the blower motor itself. when you said the gauge drops when its in drive and slows down to below 20 that is when the low idle comes back in.your blower motor for what ever reason is drawing alot of current and the alternator cant keep up at low idles, then when you put it in park it idles up enough to pick up the slack so to speak. alternators generally cant generate much current below around 800 rpms.

 

When putting it on the road again I would replace both the pos and neg battery wires with new.
Good luck.

 

Mine does that too. Anything but Park makes the voltage drop to about 11 or 12 and when I drive its about 14. When my heater blower is on the oil pressure goes up to about the A in normal but when its off its about the O or R area.

Sorry, this was just a close thread to the same issue. Just curious.

 

when the blower is on any speed it does this, just gets worse the higher the blower is set...i dont really see a difference in idle between park and drive at a stop...ill have to look closer today


the pos cable is new...this thing will more than likely be getting a new cab next spring so im not worried, ill have to got through all that crap then anyway