Blower fan issues

[68C10HotRod]

I seem to be having issues with my heater fan & don't have a clue why it's doing this. My boy was telling me that the fan was matching the motor revs this morning. Take off & running & the fan seems to do fine. Come to a stop & it pretty much stopped. Back & forth all the way to school like this.

I have previously swapped out the OEM for the PM-102 that some have suggested. When I first did this swap, it seemed to work just fine even without the engine running - not for months now. Any ideas or help. TIA.

[dan42]

Wow. A variable speed fan. My guess would be that the current to the fan is increasing as your engine speed increases, but I don't think there's supposed to be a resistor in the hot wire to fan. Hopefully someone will be able to help you with this.

[Wrenchbender Ret]

Sound's like you might have a voltage problem. Either a bad battery or alternator. Make sure your gronds are good from the frame to engine & to body. Put a voltmeter on the bat. With the engine off & the light's on it should be 12-12.5 volt's Turn off the light's & start the engine. The voltage should go to about 14 volt's & stay there at idle. If it goes over 14.5 you have a voltage regulator problem of overcharging.

[68C10HotRod]

Well, it read about 13.6 ignition off & headlights on but it dropped rapidly to about 12.3 by the time I took the leads off within about 1 minute. Started with headlights off & it read about 12.6 initially but rolled up to about 14.05 & was pretty stable between that & 13.6. It stayed about 14 but did drop down as low as 12.9 or so but immediately jumped back up to 13.9-14 again.

So does this all sound normal? On the engine grounds, it has a cable directly from battery to block & then from block to frame. I put these on & cleaned the locations a few months back so they should be good. BTW, this was strange - the first time I went to pull the headlights on to test, they WOULDN'T light up. Then after driving somewhere before it got dark, did the test again after getting home & everything worked fine - STRANGE.

Thanks for the info so far! Any ideas?

[Longhorn Man]

Are you sure it is actually blowing? It sounds like the blower isn't on at all and you are just getting air blowing through the system

[gkesseru]

Sounds like your cab itself may have a bad ground. The intermittent light symptom is an important clue. Sometimes the only ground on the cab is through a throttle cable. There should be a cab to frame ground somewhere under the passenger side. Mine is from the front cab mount support channel to the frame.

[68C10HotRod]

Well Longhorn Man was onto part of the problem. The blade connector on the fan was loose & came out of the fan. Put in a new fan, still no blow. I did check continuity between the cleaned up ground on the fan housing with the ground cable tied to the frame by the engine - got tone. I'm really at a loss with this damn thing. The dash lights stopped working a couple weeks back after I R&R the cluster. Even pulled it & replaced all the bulbs today. Still all dead & all but 1 bulb toned good. Well the right turn indicator stays on because the front running light is out.

BTW, sometime in the spring I made a good cab ground strap to frame connection with a new strap. In fact, I put a new strap on the core support, under the cab, and the box. I'm ok with all the mechanical stuff but wiring just seems to haunt me.