Mixed heat

Hi, Im at my wits end. I have searched and searched. Other people have posted this subject, even recently, but there are no answers that i have found.
I have a 97 without dual heat controls, but i have mixed heat coming out the vents. Hot out the drivers side and luke warm out the passenger side face vents.

The floor vents both blow out luke warm at best and thats the drivers AND passenger side.
i have restricted flow from the floor vents and the passenger face vents! I say restricted flow, it does increase with the blower selector but just not as powerfull as the drivers side vents

All i can add is that when i give it loads of revs, the drivers vent gets red hot (if your hand is over the vent), but then cools abit when you go back to idle.

Ive flushed the system including the heater core, and changed the thermostat and water pump but its only the drivers face vents that im getting decent heat from.
The demister clears the windscreen and i believe that works ok??

please can anyone help me out

Your location is UK. That must mean that your vehicle is Right Hand Drive, so your HVAC is a different (albeit similar) unit than most of us have on this side of the pond. Correct? Just pointing this out to help diagnosis!

thats right, it is right hand drive. As far as im aware its the same set up, with perhaps certain things having different arrangement. I know that there are posts on here and different forums that ive managed to find about this issue of mixed heat. Someone on here a few weeks ago had a very similar problem of driver side ok, passenger side $hit, so i know that it does effect left hookers aswell. Its the first time that ive posted my own thread regarding this on here as it was only last night thats i realised this issue of increasing the rpm's to about 3000 rpm's increases the heat on the drivers side to HOT HOT HOT!! And was hoping that might offer a slight clue.
The engine gets up to temperature within 3 miles when its well below freezing outside. At that point when i turn the heat on i get this problem. The flow rate from the passenger side is kinda intermittent, sometimes its the same flow rate on all power settings, usually its half the flow rate of air. The same with the feet vents. Also Usually the passenger side is half the heat of the drivers side, sometimes it has a massive difference, like practically no heat from the passenger side???

THis is just a theory and I could get NOMINATED for it but here it goes.

So you say it gets warmer when you press the gas. Here is what I am thinking the Water pump is spinning faster and applying more pressure going through your Heater core. Your problem lies in that your heater core has a lot of build up and probably needs to be replaced. Your heats starts working because The hot water is actually making it through the heater core with added pressure of the pump spinning faster.

Does this theory make sense. Iknow it is a tuff job but I think you would need to replace the heater core.

NNNOOOOOO,
That is not what i wanted to hear. I did fear it maybe the case but i didnt even wanna mention it. I was kinda hoping that i had a block in my system somewhere and the increase in rpm was pushing adequant amounts of coolant into the core, but its an open system and i guess that cant happen?? How that would effect the mixed heat in different vents i still dont know. The posts that ive read with similar problems there doesnt seem to be any answers and the OP's never seem to get back to say what they done or how they fixed it!

Best bet then is to PM the op of that particular thread and ask him what he came up with. But then again alot of users will just post up a problem until it is fixed then not sign back on again till they have another problem.

You can try flushing the radiator and pushing some fluid through the heater core by taking off the hose and sticking the water hose to it. try and push out alot of the gunk.

Also if you do this don't use alot of pressure or you will create a leak in your heater core then be forced to replace it.

Hi,
Thanks for the input, Ive pm 4 people over the past week but havent heard anything yet, but most of the posts that ive seen are way old.
Ive only had the jeep since last spring and i BELIEVE that the heater was working fine at that time. Ive since flushed the system and the heater core.(it was very VERY nasty)
I get flow in both directions and clear water straight away when i last done it. However ive never burped the system, Could there be an air lock in a open system?? I could make do with red hot heat from the drivers side if it was on permanent until the summer months when i could look into the other perhaps unconnected matter of mixhed heat.

Have you tried feeling the temperature in the heater hoses (both inlet and outlet) under the hood (or I believe you may call it the bonnet). Don't know if your year has a vacuum operated coolant flow control valve in the heater hose, but you could look for that. I think they can be locked into the open position with wire. If core is not blocked both hoses should be hot. Then rev it like you say makes it hotter and feel hoses again.

Also, what ive established from other threads that have been completed, with regards to increase in heat with RPM, were air locks, (I found 2 examples of this, both closed system)

and on one occasion incorrect mixture of coolant (too thick a coolant that the waterpump couldnt cope with at idle). Im pretty sure my coolant is 50/50.

but no results that i could find regarding this mixed heat.

Hi winterbeater, (i hope your name is a good omen here)

There is no heater control valve on my car, i believe that went out in 96. Coolant is meant to be constantly going round the matrix.

Both heater hoses get hot at idle. Top heater hose gets hot so i can squeeze it hard for about 3 or 4 seconds max before i get burnt. The bottom heater hose slightly longer maybe 7 or 8 seconds. If i rev it then i cant squeeze hard either hose for any more than a second or two because there both too hot.

I think your heater core is clogged up.


Have fun replacing it lol. Bit of a PIA.

The outlet heater hose wouldn't get that hot if the core was plugged (internally). Plus, you already did the heater core flush. I suppose that the heater core could have a lot of surface debris preventing airflow through the core. This usually starts to collect in one corner or the other and can eventually block it off. One symptom of this is a musty odor. -- (warranty engineer experience). Air through a partially blocked surface could flow more to one side or the other. Are any of your doors (level or temp or recirc) vacuum controlled? That could be RPM related.

O.k

Is this widespread agreement that my heater core needs replacing????
it isnt leaking, and i do not get steam in the cab. I understand that it may well be the heater core, but im obviously gonna try and get some other ideas to this to try first hopefully starting with the simple stuff.
Ive just read up on burping the system and as i understand it, it USUALLY applies to the closed system, has anyone with an open system ever had problems with air lock??
My temprature gage shows fine with no tell tale signs of going up and down.


Also some more history which may help with more clues. When i initially flushed my system, i done it incorrectly. But then I changed my thermostat.

I then realised that i had not flushed properly and then flushed again and loads more gunk came out with the new thermostat in. I then flushed my heater core, again, with the new thermostat in and got gunk out. All i have in my coolant system now is nice green coolant. However, Could this have clogged my thermostat partly helping cause this heat/rpm problem on the drivers side, Even though i seem to get up to good engine temprature within a few miles in these very cold conditions?

As it stands, this is gonna be my first port of call, new thermostat, and then burp the system. Does this sound reasonable? Any other ideas that you may have i would be VERY THANKFULL. And i promise that whenever it is i get this sorted, ill post the results of what the cure was, even if its the new heater core!!!

I don't really think it's the heater core, unless one side of it has external debris blocking air flow to one side. Both sides of your hoses are hot. Can't be thermostat either. Engine gets hot.

But I don't see how you flushed and it had anything to do with the thermostat. Did you disconnect the heater hoses at the water pump and thermostat housing and flush by running water in through hose that came off tstat hsg?

on the 97->, it's relatively common for the little plastic arm that connects the vacuum actuator to the hevac blend door(s) to break off-on both xj's and tj's. when that happens, you'll end up with weird/no/uneven heat between the driver and pass sides. stick your head way up under the dash, find the two(?) vacuum motors and make sure the plastic armlinkthings are still connected properly. my bet is one of them is busted.

this link shows exactly what i'm talking about:

http://www.jpmagazine.com/techarticles/electrical/154_0801_jeep_wusses_quick_heater_fix/index.html

winterbeater,
first the temp im pretty sure has only the cable to operate it, ive checked the movement under the dash and this seems to work fine throughout the cycle. The level and recirc i believe are vacuum operated. I get suction from the lines.

regarding the thermostat, I flushed (without backflushing) then fitted a new thermostat thinking all was good. Then i flushed properly, wasnt sure if i dislodged some gunk that made its way to the stat somehow that was restricting coolant flow at idle?? but like ive said i have no overheating issues at all.

HELLBENT

does the dash need to come apart for the check that you are talking about. It sounds like possibly the right track as my heat is definatley wierd. How can i have red hot heat under high rpm from the centre console (drivers side vent), and luke warm from the passenger side centre vent, its all part of the same ducting??
Today i had very reasonable heat at EVERY vent at 3000rpm together with the same rate of air flow!!???
now that is just weird!!
I shall look into what youve suggested further

hellbent,
ive just had another look at the link that you stuck in, do you know if that site goes onto explain how they do it or is it just those two pictures? There doesnt seem to be too much of an explantion as to what to do.

Also im trying to work out where it is that im looking, here is a picture of inside my glove box with the door off. I believe that this is getting close to where i need to be looking, but this is all i see.

Move heater control from hot to cold and from defrost to vent to floor, and you should be able to see what moves (or is trying to move) what.

dunbad said:

hellbent,
ive just had another look at the link that you stuck in, do you know if that site goes onto explain how they do it or is it just those two pictures? There doesnt seem to be too much of an explantion as to what to do.

Also im trying to work out where it is that im looking, here is a picture of inside my glove box with the door off. I believe that this is getting close to where i need to be looking, but this is all i see.

Click to expand...

you're on the right track. i don't think the box has to come out, but the lower part of the dash might. unfortunately, tj's have more room to work with. the original article was longer than that, but the online version got truncated, i guess.