Am I nuts or does every ones fan slow down when accelerating briskly (Not just when flooring it)? Mine does at even modest levels of accelerating nut only when I jump on it.

 

i think its normal..mine does it as well
Marcin

 

A lot of times what you will sense is the lack of air coming out the vents. This is because of the loss of vacuum for the HVAC controls and they will default to the floor/defrost postion when this happens. There should be enough reserve vacuum in the vacuum tank, but it you have a small vacuum leak, there won't be. I found a leak in my tank's vacuum hose just this way.

 

What is the best way to find a small vacuum leak?

 

I use a hand operated vacuum tester (like a Mighty Vac). This will let you apply vacuum to a line or device. You can then see if the device operates or the hose holds vacuum.

 

I was told there was a senosor to kill the A/C under acceleration to get power back. If not i have a vacumn leak, where is this vacumn tank at. I already have had problems of going through those damn a/c check valves. It took me at least 5 of them before i got one that didnt crack.

 

Well Rob as usual you are a wealth of information. Let me ask you, I have a problem with the AC position where the air should come out of the top and the floor at the same time. In only that position there is no top side air flow and very little floor air flow. The other 2 AC positions appear to work correctly. Could this be related to the leak you speak of?

Where is this reserve canister? I haven't yet had a chance to search for it in my shop manuals yet. Where are the hoses I would need to check for vac leaks, under the dash?

thank you so much for your help.

 

Here is where the reserve tank is. What I do to check all the portions of the HVAC system easily, is to go to the check valve and pull the hoses off one by one and use the vacuum tester on them to see if they hold vacuum. The line to the manifold would have to be removed at the manifold and temporarily plugged to do this.

What happened to me (and I have seen it happen to others), is the line going to the tank had a spot rubbed through it by where it turns at the bottom of the battery. I replaced the line (which BTW, goes through the convoluted tubing of the wiring harness) and put something over the spot on the chassis where the hose was rubbing, so it would not happen again.

What tipped me off that I had a leak was my IAC counts were extremely low at idle. This meant the engine was getting air from another source.


BTW, it is the compressor clutch that disengages at WOT, not the blower fan, so the only thing you might notice is the air is not as cool (not a change in blower velocity).

 

Ohh there is a definate change in the velocity in the a/c most of the time. I think the valve may be leaking again, can i get a metal one anywhere? They keep on cracking. I will check these lines out to find the problem.

where can i get new lines from, Thanks

 

Fbird, what check valves are talking about? The only valve I'm formiliar with is the thermal expansion valve. Can you post a pic of where they are?

Rob, is the check valve with all the hoses located in the dash by the AC controls? Does the shop manual have typical IAC counts in it so I can monitor them as you did?

Thanks

 

This is the check valve I'm talking about. You can see the a/c pipes right next to it.

Hot idle IAC counts generally are in the range of 20-40 depending on mods and engine condition. When I had a leak, it was going way under 10 and sometimes to 0.

 

Thanks your a big help. Hope I can return the favor some time. Need any help with your lawn mower. I can do that LOL

 

How much for a valve job on a 17 hp Tecumseh engine?

 

I charge at about $70.00 dollars for the whole job with parts give or take. Be careful, a running joke in our business is that Tecumseh's come with a hole in the block when you buy them. You can do it yourself it's a piece of cake. Just let me know if you need specs. I can look them up for you.

hey I checked the IAC just a little while ago and it started out high until it warmed up and then never went below 43. Does this mean there is no vac leak or should I still look for a leak?

Thanks I meant it about the specs you need it, I'll get it to you. If you need parts for mowers or engines I'll UPS them to you at wholesale. Just say the word.

 

Wow this happens to my car also. The cold air switches to the floor for about 3-5 seconds and slowly comes back to the vents. I thought this was normal also. ??