Blower switch - all or nothing

[JZLAJeep]

Disclaimer up front, this is on our '95 XJ, but same hardware as the MJ. Noticed the last couple times driving it that the blower is off unless in the switch is in the highest position. Is this indicative of the switch going bad?

 

If so, replacing the switch may be a good time to also fix the non-working oil pressure gauge and burnt out backlighting bulb.

[gogmorgo]

Generally this is a resistor issue. 
The highest position on the switch sends full power to the blower motor. The lower fan speeds feed through a combination of resistors to achieve reduced voltage and lower fan speeds. If the resistors burn out you’ll lose some of the speeds.
The blower motor resistor pack is pretty cheap and easy to get to under the passenger side dash. 
If the blower motor is getting old it may have internal shorts that cause it to pull excessive current, which can lead to premature failure. Same if the bearings are failing or there’s something obstructing the fan and slowing it down. It’s worth investigating at the very least. A lot of places will recommend replacing both resistor and blower motor at the same time, but you can buy a bunch of resistor packs before adding up to a blower motor, and resistors do eventually fail over time or if they get covered in dust or something that holds the heat in.

 

Not saying it couldn’t be the switch. They should be available pretty cheaply too. Napa had a listing last I checked, I’m sure other places do as well.

 

Oil pressure gauge is more likely to be a sending unit than the gauge itself. If there’s oil leaking out of it its definitely time to go. The way the failures start to go is they’ll start dropping out intermittently, and start seeping oil, and eventually will pop and start gushing the oil out. Cause its on the pressurized side of things you’ll pump out the full volume of oil from your pan in a matter of minutes, if you even get that long.

[JZLAJeep]

Good advice. The blower motor has been going for a while and we have a new one, just haven't gotten around to putting it in. But, on a 28 year old vehicle it's tough to say that anything wore out prematurely. Actually have two new blower motors to put into both XJs. We'll replace the blower resistor too when we put in the new blower motor. 

[gogmorgo]

Yeah, at that age everything starts becoming a wear item. But once you replace everything you’ll have a new truck, right?

 

Blower motor is pretty quick and easy too. 15 minute job, it’s just in the engine bay, passenger side of the firewall, not buried in the dash somewhere. Three fasteners and the connector. Don’t miss the gasket in there. I just did one of mine and didn’t notice it was still stuck to the old motor until I already had the new one in place. And I won’t tell you how long I had the new one sitting on the shelf.

[ghetdjc320]

Also check the connector on the blower motor switch. 

[schardein]

Yes, check the blower switch connector.  It's common for them to be burnt and melted even if everything else seems to be working ok.  If you have problems in the system, it's even more likely the switch connector is also compromised.

 

https://www.ebay.com/itm/233456730333?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=bpFa1QANQb2&sssrc=2380676&ssuid=bpFa1QANQb2&widget_ver=artemis&media=COPY

 

https://www.ebay.com/itm/334256319949?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=bpFa1QANQb2&sssrc=2380676&ssuid=bpFa1QANQb2&widget_ver=artemis&media=COPY

 

https://www.ebay.com/itm/234400215688?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=bpFa1QANQb2&sssrc=2380676&ssuid=bpFa1QANQb2&widget_ver=artemis&media=COPY

[JZLAJeep]

Thanks @ghetdjc320 and @schardein. I'm sure damage to that connector will be obvious when we replace the blower motor. Saw a melted blower motor connector when the blower motor on our Ford Expedition went out this summer, so we've seen it before...

 

Pictures from the Ford: