First off my truck is an 87 Laredo. Also, the regulator that controls the speed of the fan is burnt out (I think). Unless I have it set to full blast it will pop fuses. Not sure if that is part of the problem.

I have been trying to figure this one out but I'm completely stumped. There are a couple of problems with my heater system that I can't seem to figure out. When I have the heater off there seems to be cold air blowing in from the passenger side foot vents (seems to do it no matter what the fan speed is). When I turn on the heater it will start blowing air in from the passenger foot vents at what ever speed the fan is set to. I will blow a constant stream even if I have it set to vent or defrost. The weird part is that if I have it set to vent (and have the temp set to heat) it will blow warm air on the passenger side. Same with defrost. Also, when I am sitting at a light and I have it set to blow heat the air coming out on the drivers side (that is hot) will cut out, yet the passenger side will continue to get a blast of cold air.

If that doesn't seem clear let me know and I will try and explain it better. Since it's kind of a weird problems I have a hard time explaining it.

 

replace the blower motor resistor above pass feet check the vacuum line from ball behind front bumper to the motor and firewall on pass side below coolant bottle by blower motor

 

Got it, I will go ahead and check that out tomorrow.

Just a quick question, do you think that would contribute to the air coming into the cabin from the passenger side foot vents even when the blower is off?

 

it might never heard of air coming in on just one side

 

Since it's been a bit I thought I'd bump this up. Still can't figure out what the problem is, maybe someone has had a similar issue. I am about ready to give up on this thing, and try to get another Jeep, or even a 4runner, lol. This is my first experience with a Jeep, and lets just say it hasn't been a great relationship. this is just but one of many problems...

 

I think I have deduced the source of the problem... Someone kicked my %*^$@$# heater! I guess some a-hole put their foot through the plastic box that holds all the heater components before I got the truck. While I was sticking my head under the dash to see where all the foot vents were I noticed a loose piece of plastic about 6 inches across. Guess that would cause a bit of a draft coming from the passenger foot well...

 

Also. Check the slide door for the vent and flow control. It's deep in your dash so prep for a lonely evening

 

24 year old vehicles are going to take some maintenance to be sure.

But take one thing at a time. Address it in a methodical TESTING based strategy and you should be fine.

And be sure you have a manual. Factory service manuals are the best. (ebay) Then comes Chiltons, In last place and for good reason, are Haynes manuals. I like Haynes underwear, I hate Haynes manuals!

The good thing about a 24 year old vehicle is that it gives you opportunities to learn! Glass half full deal.

If you haven't run across this link yet, check it out. It should be bookmarked. It has a lot of good information on testing things on the 87-90.

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

 

I think I am getting this jeep back together. I just finished changing out the radiator, and this will probably be my next project. I'd already decided I wanted to swap out the interior including the dash (it's not in the best of shape, and burgundy isn't my thing). So I'll be swapping out the heater equipment at the same time.

P.S. Thanks for the link. And yeah, I can agree with you on the manual. I'm not unfamiliar with working on cars, and have noticed I prefer Chilton as well. Luckily my truck came with one, but I want to get a service manual sometime soon as well.