[ziggy]

Heres the skinny;
1997 gmc 3500 diesel with no power to what I think is the heater fan,What Im wondering is how many wires or where is the power wire for the heater fan? Looks like the squirrel cage on the right hand side of the heater but i can only see a purple and a black wire coming out,the rest is a rats nest of wires.Its the only vehicle we have left going at camp and day 6 of a blizzard so dont want to take any chances running a 12 volt wire to the purple one and blowing something,also the truck was sitting outside here in arctic conditions since september but is now inside a shop and not toasty but not froze either.All the fuses are good and power at the fuse box is also good.
Cant find a manual or any info online so any help would be appreciated.If the heater only has a hot wire and a ground then I will know to try the hot one with a reliable 12 volt source and take it from there. Any takers?

[SprCForr]

Ziggy,

All I can get you is a copy of the schematics for a '98.

[CapeApe]

if you have a meter do a continuity check between the fuse block and heater and then the heater and ground

[CapeApe]

a common problem with heaters is that the variable resistor is prone to blowing and bang no heat

see above schematic

[ziggy]

Thanks a ton man,much appreciated.

[grainfedprairieboy]

Ziggy. I've got a couple 3500s in the fleet one of which is a 98 but gas. On that one we took the wrap around cover off so the outside metal of the housing was exposed and we hit it with a hammer everytime we need it. We have been doing this to that truck for two years as we could find no wiring problems

[canadian1971]

I had a car that lost the heater core......I went out and bought a little heater that plugs into the cig lighter.....worked better than the heater ever did...plus you can aim it where ever you want it.

[ziggy]

CapeApe CapeApe:

if you have a meter do a continuity check between the fuse block and heater and then the heater and ground

Continuity was good,the resistor also checked out ok.Put a hot wire to it and just sparks.Were thinking the fan.

[ziggy]

canadian1971 canadian1971:

I had a car that lost the heater core......I went out and bought a little heater that plugs into the cig lighter.....worked better than the heater ever did...plus you can aim it where ever you want it.

This was the thermometer 2 days ago,dont think that will cut it.

[ziggy]

grainfedprairieboy grainfedprairieboy:

Ziggy. I've got a couple 3500s in the fleet one of which is a 98 but gas. On that one we took the wrap around cover off so the outside metal of the housing was exposed and we hit it with a hammer everytime we need it. We have been doing this to that truck for two years as we could find no wiring problems

We'll try that tommorow,going to take 2 weeks to get one flown in so anythings worth a try.The boss is talking about throwing a gen set in the back and take out the back seat for some big electrics.Red green would be proud. Amazing the jury rigging we have been doing the last week,anything is usefull right down to the s hooks of the broken bungie cords.Still my cats the only thing really running.

[canadian1971]

ziggy ziggy:

canadian1971 canadian1971:

I had a car that lost the heater core......I went out and bought a little heater that plugs into the cig lighter.....worked better than the heater ever did...plus you can aim it where ever you want it.

This was the thermometer 2 days ago,dont think that will cut it.

Well this was in Leif Rapids Manitoba......just south west of Churchill.....got down to -40 there all the friggin time.....worked like a charm for me....just dont leave it running when your vehicle is shut off....that could cause some trouble.

[ridenrain]

I used a coleman 2 burner stove in a VW bug for 100 mile house, but I wouldn't suggest that.

[grainfedprairieboy]

ziggy ziggy:

grainfedprairieboy grainfedprairieboy:

Ziggy. I've got a couple 3500s in the fleet one of which is a 98 but gas. On that one we took the wrap around cover off so the outside metal of the housing was exposed and we hit it with a hammer everytime we need it. We have been doing this to that truck for two years as we could find no wiring problems

We'll try that tommorow,going to take 2 weeks to get one flown in so anythings worth a try.The boss is talking about throwing a gen set in the back and take out the back seat for some big electrics.Red green would be proud. Amazing the jury rigging we have been doing the last week,anything is usefull right down to the s hooks of the broken bungie cords.Still my cats the only thing really running.

Take it out and put it on the bench. If you can run a Pos/neg to it and run it then the problem is in the control switch/fuse/wiring. It is rare for any electrical motor to just suddenly stop working so seriously give it a few sharp taps with a wrench or hammer especially around the bearing housing.

[Banff]

Yes if the fuses are fine and the fan does not work it is the fan which needs replacing . Quite often this is the case even before the on dash switch connections fail . Grab a fan from any vehicle , I don't think it really matters what kind .(Temporary until a new one arrives)

Sometimes dropping to many cigarettes , lighters , pens , screws , etc and even ice or dirt through the dash vents can cause the vent to not open and close . Do you get any heat coming from anywhere top or below dash ? Also do you seem to get more heat as you travel faster or slower ? I know these are simple questions but if so it is your fan no ands ifs or buts ....replacing a heater fan is easy , although sometimes getting to it can be complicated depending on it's location .

I really doubt the wiring has anything to do with it unless it is the dash switches .

[grainfedprairieboy]

Banff Banff:

Yes if the fuses are fine and the fan does not work it is the fan which needs replacing . Quite often this is the case even before the on dash switch connections fail . Grab a fan from any vehicle , I don't think it really matters what kind .(Temporary until a new one arrives)

Sometimes dropping to many cigarettes , lighters , pens , screws , etc and even ice or dirt through the dash vents can cause the vent to not open and close . Do you get any heat coming from anywhere top or below dash ? Also do you seem to get more heat as you travel faster or slower ? I know these are simple questions but if so it is your fan no ands ifs or buts ....replacing a heater fan is easy , although sometimes getting to it can be complicated depending on it's location .

I really doubt the wiring has anything to do with it unless it is the dash switches .

Actually, if your temperature rises and falls with vehicle speed it has nothing to do with fan and is indicative of either low radiator fluid or a dead battery with the vehicle running directly off alternator.