Thermal fuses

I have an 04 dodge Grand Caravan and the front HVAC blower motor quite.

Did a bit of teching and found the thermal fuse in the blower motor resistor pack is open.

New resistor pack is ~$90 I have located a ton of replacement substitutes but I need to know the current and temp rating for the replacement.

Any help would be appreciated on the specifications or where I might source the information.

An aside there seems to be a lot of fuse links in the van and no info on the rating.

TIA

Reply to
NotMe
Loading thread data ...

Bridge an ammeter across where the thermal fuse was. Find out what the starting current is. Now, pick a Polyfuse that is rated for 1.5 times that current. The polyfuse will give better motor protection and won't fail, but it will cost more than a simple thermal fuse.. maybe as much as two dollars.

--scott

Reply to
Scott Dorsey

I burned out two or three resistor packs for my Dodge full size van before I "got it right".

Dont know if his Grand Caravan is similar, but would suspect it might be.

These resistor packs often burn out when the fan motor is having some internal problems. You may not notice the problem other than for the failure of the resistor packs. The current consumption can vary a lot, and go up much higher than was designed for the circuit. In this case, the long term cure is to change out the fan motor and replace the resistor pack.

In my case, I drilled into the resistor pack and installed an external 20 amp fuse across the "burned" connection. This fuse has never blown, so I believe I am safe enough to install a new resistor pack (if I ever need to do so). Since it works so well, there has been no incentive to replace it.

Reply to
HLS

thanks, we have several Grand C's in the extended family (foster to adopt) from 04 to 06 max current is 13.5 amp give or take.

Is a Polyfuse a brand or a type (perhaps what I'm calling a thermal fuse) as I suspect the fuse is not only for current over load but over temp as well.

Reply to
NotMe

If you are sure the motor is good, pick that as a good baseline and get a fuse that pops at 20 amps. If you're going for the polyfuse you could probably use 15A.

Put a little light machine oil on the bearings og the blower and see if that current drops a little bit. If it doesn't, don't worry.

Polyfuse is a sort of resettable thermal disconnect that is based on a material that is conductive when a solid but insulating when a liquid, so the I/V curve has this abrupt discontinuity where it suddenly goes open when the current or temperature exceeds a certain amount. It's a Raychem trademark.

Other companies make clones of the thing, but Mouser carries the original Raychem ones.

--scott

Reply to
Scott Dorsey

The current draw can vary wildly if the motor is bad. It can be hard to know for sure the motor is the problem because you may not see any overt symptoms. They can be seen with an o-scope, for example, but you may not see the problem with a simple current draw test with a VOM.

You may not hear any noise from the motor nor have any other indication.

I dont remember, right now, why I chose a 20 amp fuse. I think it was a compromise between what the motor should draw and what I thought I needed for protection to the resistor pack.

Reply to
HLS
******First, I replaced the fan motor, then

Reply to
HLS

Reply to
man of machines

Best I could find was $87.50 and when I went to pick it up the part was on "back order".

I've patched the old one and am seeking a replacement for the thermal fuse.

: : Scott Dorsey wrote: : : > In article , NotMe wrote: : > >I have an 04 dodge Grand Caravan and the front HVAC blower motor quite. : > > : > >Did a bit of teching and found the thermal fuse in the blower motor resistor : > >pack is open. : > > : > >New resistor pack is ~$90 I have located a ton of replacement substitutes : > >but I need to know the current and temp rating for the replacement. : > : > Bridge an ammeter across where the thermal fuse was. Find out what the : > starting current is. Now, pick a Polyfuse that is rated for 1.5 times : > that current. The polyfuse will give better motor protection and won't : > fail, but it will cost more than a simple thermal fuse.. maybe as much : > as two dollars. : > --scott : > : > -- : > "C'est un Nagra. C'est suisse, et tres, tres precis." :

Reply to
NotMe

Try Raychem part RUE300. Mouser should stock it.

--scott

Reply to
Scott Dorsey

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.