Newbie with HVAC Problem

jhowell0o · Post by **jhowell0o** » Thu Dec 21, 2006 7:37 pm

Hi all,

I have a 1998 S-10 Ext. Cab. My heat only blows out the front vents. It will not blow out the floor or defrost. I was searching the forum for help and everything I read talks about the a/c transfer case switch. What and were can I locate this? Is this what I need to check? I am clueless!! Any help would be great. Thanks

Post by **HenryJ** » Thu Dec 21, 2006 7:43 pm

Welcome. I assume you have a 4x4?

This post shows the switch and its location on the transfercase - NEW TRANSFER CASE VACCUM SWITCH

jhowell0o · Post by **jhowell0o** » Thu Dec 21, 2006 7:48 pm

I dont have a 4x4 so I dont have a transfer case. So I am not sure what to check. Thanks for the quick reply.

Post by **HenryJ** » Thu Dec 21, 2006 7:52 pm

Well if you don't have a 4x4 , you don't have a transfercase, or the transfercase switch

You need to look for vacuum leaks. Not easy. A can of carb cleaner sprayed around can be helpful. Look to the lines across the firewall. Check the reservoir in the RH fender.
If everything checks out, you may need a new control? Is it auto temp control, or manual?

jhowell0o · Post by **jhowell0o** » Thu Dec 21, 2006 7:57 pm

It is a manual control. Thanks for all your help!!!!

Post by **HenryJ** » Thu Dec 21, 2006 8:05 pm

I haven't heard of lots of control head failures in the second gen, but it is very possible.

I would do my best to check the function or lack thereof for the vacuum pots that operate the HVAC doors. One that is stuck, or a bad diaphram, could cause problems. You should hear a leak if that is the case.

I would probably save the control head replacement as one of the last things. Really do your best to diagnose a vacuum leak. The tubing gets pretty oxidized after half a dozen years.

jhowell0o · Post by **jhowell0o** » Thu Dec 21, 2006 8:45 pm

Where can I locate the Diaphram?

BADs Crew · Post by **BADs Crew** » Fri Dec 22, 2006 1:41 am

Look at the Hot Floor Vent Fix at the right of the main page. This will show where things are.

F9K9 · Post by **F9K9** » Fri Dec 22, 2006 1:43 am

I know this sounds really stupid but, the same thing happened on my '97 ZR2. The control knob was stripped out. Try pulling it off and putting your temp control knob in the place of the selector and turning it.

Post by **HenryJ** » Fri Dec 22, 2006 5:29 am

jhowell0o wrote:Where can I locate the Diaphram?

These are the slave vacuum pots that operate the doors in the HVAC. They are not repairable IIRC. You would need to replace them if they have a bad diaphram.
Basically listen for leaks.

f9k9's suggestion is a good one. Sometimes simple is the logical answer. Ask yourself these questions first and look for simple things. Did I do something that may be the problem? (stripped knob, pencil down the defroster duct, kicked the HVAC, tried to make an adjustment with a BFH, etc.) Will warranty repair this? Look , listen and feel.

jhowell0o · Post by **jhowell0o** » Fri Dec 22, 2006 11:02 am

Well while examining the vacuum hoses I broke a t-valve. So I went to the auto parts store bought a new one and while examining the broken t-valve I noticed it was clogged. Bought a new one, put it in, and now I have heat on the floor, defrost and front. All works now!!!!! It is amazing how you break a part when examining it, and it was the defective one all along.

THanks for all you help!!! You guys really know how to treat a newbie!!

Josh

Post by **HenryJ** » Fri Dec 22, 2006 11:47 am

Glad you found your problem!