Air was not very cold today so I broke out the guages and temp probe.sucction line was showing 56 degrees but I could n o t get less than 77 out of the vents. I recently installed a new hot water shut off so I pinched the hose and the temp really got cold, super I thought but when I pulled the vacuum line there was no change on the new valve. Seems I now have the pleasure of finding a leak! Hopefully I find it and that will solve my idle hunting as well!
What are the chances of the heater valve not closing all the way?
You can test the valve in situ. Valve should shut completely.
Not sure what you mean. Does the valve open with vacuum or close with vacuum? Do you have vacuum?
I can close the valve by hand but it is difficult there is some vaccum I think but I am unsure as to when it should be open or closed when runnig. I pinched the hose and the temp dropped I didnot nptice any change in valve with vaccum hose removed
The valve is very hard to move. Even by hand! I think it would take ALOT of suction to move the valve, is it possible that I got a bad valve? Or was I supposed to do something before I installed the valve? I do have suction but not nearly enough to move the valve.
I called coventry west, (us) they are sending a replacement valve! Hurray! I hooked my vacuum pump from work direct to the valve and it still wouldn’t move without serious help.
Keep in mind some XJ40s (my 1990 for example) have no heater valve. The system relies on the blend flaps to change from heating to cooling. I still wonder if hot water running through the climate control assembly has an impact on the efficiency of the cooling mode.
It certainly does have a bad effect on the cooling efficiency. On my 91 which did not have such a valve, the A/C was just about adequate for a temperate UK summer - and then the compressor failed so I drove for a while in winter/spring with no A/C at all and with everything set to ‘cool’ the cabin temperature became unbearable after a few miles.
I like the idea of putting a shutoff valve in the heater hose, off in summer on in winter.
David …
The water shutoff valve on the heater hose is held CLOSED by vacuum. I Imagine the thinking being that if the vacuum to the valve or the valve itself fails you won’t freeze to death during really cold weather.
Similarily the air intake door on the two fan assemblies fail to the “fresh air” position which means that you’re constantly trying to cool hot outside air instead of colder cabin air. When I rebuilt my system both assemblies
had failed to the fresh air (outside air) position. On one the vacuum actuator had failed and on the other vacuum was not being supplied to the actuator. So I was constantly trying to cool fresh but hot outside air.
Thanks Gman, any way to visually verify the external air flaps are closed? I live in southwest Fl and my a/c has 2 settings, max air and off.
That wold be in my truck , not sure on the cat.
David …
Unfortunately the two blower units are really buried underneath the dash. As a minimum you would have to remove the panels under the glove box and steering wheel and then I’m not 100% sure you could see or feel if the recirculation doors are open or closed.
If you’re not familiar with the units here is a picture of the one on the left side and the right side unit is just a mirror image.
As you can see, the door is all the way up at the top of the unit. It’s shown in the closed or “fresh air” position that draws outside air in from the hole in the top of the unit. The door simply pivots up 90 degrees and closes off that hole and then recirculated cabin air is drawn in.
In this picture you can see where all the old gummy foam on the door has broken down. All that foam ends up on your evaporator fins and will slowly blocks the air flow.
Thanks for the pic, I haven’t bothered to put the lower panels back on chasing other issues. I did have the right hand unit out when I got the car because the motor was stuck, I spun it free lubed it and put it back,should have done more then but I wanted it on the road. Just doesn’t seem to cool the car down quickly. Also doesn’t seem to move a large volume of air? 3 speeds work and it is on manual.?
David …
If your fans are roaring away at top speed and you’re not getting a lot of airflow (cold or otherwise) it points to …
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Just one fan running and blowing it’s air across into the inoperative unit (poor design!). If you determine that’s not the problem then …
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One or both of the blend doors in the evaporator housing are not moving into the correct position, or …
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The face of the evaporator core is blocked with decades of dirt and debris (and recirculation door foam)
Or a combination of 2 and 3.
As I recall someone once posting a picture of the box built into the bottom of the dash top that the system uses as ducting (another poor design) coming apart and allowing the air to leak out.
The trouble with cleaning the evaporator core is that there is really no way to get to it without removing the housing, which is one serious job. Without doing that you’re never going to get cooling the way the system was designed. When I removed my evaporator I was shocked how dirty it was and just how much cleaning it required … but what a difference !
Looks like I need to pull both blowers, I read you can get some access to the evap thru there, at least I can get a glimpse and maybe clean it from there. Removing the dash os one option I really don’t care to think about.
David …
I’m sorry to say that while you can see a tiny bit of the evaporator core thru the two holes after you remove the blower units there really is almost no access.
I went as far as fabricating a small metal tube with a 90 degree bend on the very end that I used to blow water thru as much of the core as I could reach thru both holes. After pulling out the core I could see that it did almost no good. The problem is that the grime and greasy buildup on the evaporator fins is very hard to remove. You’re not going to vacuum or blow it off. Have you ever seen how the grease and dirt builds up on the metal intake grills of your home A/C system that you remove to change the filters? Remember the grills are much farther apart then the fins on the evaporator and hopefully you clean them more than once every 3 decades.
Now that being said you may want to consider using a tube like I made and blowing a good degreaser up and thru the core using those two holes. I would do this, let it sit for a while and then flush it out with water. Try this 2 or 3 times over the course of a day and that just may do the trick. All the water will (should) just run out of the two holes in the bottom of the housing that drains out the condensation.
Since I do a/c and refrigeration on boats I am very aware of how compacted those littl buggers can get, hopefully I will be able clear it some how.
Hey gman I think it is a vacuum issue as none of doors get enough to move them much if at all.spot on about the evap access but I have some foaming evap coil coil cleaner to put on it although it looks fairly clean. I am trying to locate the vacuum non return valve to see if it it plugged. Any idea where it should be?
Located under the battery tray. Number 4 in the diagram.
Number 1 is the a/c system vacuum reservoir.