is there any updated resistor pack fo the blower motor?

[Pete M]

I know more modern rigs have more modern packs, but has anyone created an update for our old Jeeps?

 

 

[Manche757]

Do you have a pic of where that goes?   Any suggestions for replacing blower motor and fan?

[Pete M]

if I remember right it is located right above the passenger's left foot inside the duct work and held in by a pair of 8mm screws. 

 

I think there's a writeup on replacing the blower in the link in my signature.

[JMO413]

I have not seen an updated resistor. They are still available from Mopar.

[Minuit]

What updates would you want? I've always thought the OEM resistor pack did exactly what it needed to and nothing it didn't.

[AZJeff]

2 hours ago, Minuit said:

What updates would you want? I've always thought the OEM resistor pack did exactly what it needed to and nothing it didn't.

Some more modern cars use a semiconductor regulator to control fan speed, instead of just a plain voltage dropping resistor.

 

Then again, those are a LOT more expensive than the simple resistor network the MJ/XJ. Heater uses.

[Pete M]

3 hours ago, Minuit said:

What updates would you want? I've always thought the OEM resistor pack did exactly what it needed to and nothing it didn't.

 

 

corrosion resistance would be sweet. 

[Pete M]

it doesn't have to be a leak.  it can just be the humidity in the air.    the pack is just there, hanging out in the duct work.  trying to stay cool and all. 

 

edit, on a side note, those resistors get hot enough to set paper on fire.    

[schardein]

In my open CJ7, I've had some pretty bad rust form on the terminals of the blower resistor pack.  I've thought it would be good to find one that uses a waterproof connection, like most modern sealed connectors.  So far I haven't found anything.

[AZJeff]

If the resistor coils get corroded, that is no big deal.  If the CONNECTIONS to the coils get rasty, then you have issues.   

 

The connections on the "outside" of the heater box, in the passenger compartment, should be relatively immune to moisture that causes corrosion, assuming you are not submerging your MJ/XJ to the point of water getting into the heater box.

 

One KEY issue to consider is the fact that old resistor packs, when they get hot, cause the temper (springing-ness) of the female half of the "spade connectors", which are part of the wiring harness, to become loose.   Any resistor pack that has seen excessive heat should be considered a candidate for replacing the female spade terminals on the wiring harness on general principles.

[schardein]

Last pick-a-part run, I got a blower motor resistor pack from a Chevy express van.  It uses a weather sealed connector, and incorporates a relay that engages on the "high" setting to route power directly to the fan motor.  It also has 4 speeds.  I plan to experiment a little to see if I can retrofit it in my CJ.  The main issue I see, is the mounting tabs sit on a stand off (or boss) in the oem application, and not flush like the CJ.  Overcome that and it's just splicing some wires.

[Eagle]

On 10/9/2019 at 11:10 PM, Pete M said:

edit, on a side note, those resistors get hot enough to set paper mouse nests on fire.    

 

Fixed it for you.

[Manche757]

The fan on my 89MJ, 4.0 was making a loud intermitent squealing, scrapping noise, so had motor and fan replaced in last few days. After reading this thread, I had the resistor replaced also. I was surprised there is not one spot of rust on the old resistor,which I assume was original. The new one came with a cover. I assume that is to reduce the risk of fire but it would hold in the heat to build up more. Cooled by air flow, I assume.

[AZJeff]

T

59 minutes ago, Manche757 said:

The fan on my 89MJ, 4.0 was making a loud intermitent squealing, scrapping noise, so had motor and fan replaced in last few days. After reading this thread, I had the resistor replaced also. I was surprised there is not one spot of rust on the old resistor,which I assume was original. The new one came with a cover. I assume that is to reduce the risk of fire but it would hold in the heat to build up more. Cooled by air flow, I assume.

The resistor for the blower motor is a super basic electrical element.   The blower has four settings, with the top speed when it's being fed 12VDC directly. The other 3 slower speeds are incrementally lesser voltages, and they are achieved by running 12V through various resistors in the resistor network to drop the voltage down.

 

All of the resistors are fed 12V from the blower motor switch on the heater control panel, and the output of all of the resistors connect to the "B+" side of the blower motor input terminal.   These resistors are made of wound nichrome wire, and drop the voltage to the blower motor by taking 12V and turning some of the energy into heat.   This is why the resistor network is located inside the heater box plenum, so that air can pass over the wire and keep the resistors from work heat tempering too much with age.  (They WILL glow red when certain blower speeds are selected--the amount of energy being dissipated as heat is NOT small.)