HIGH SPEED ON DASH BLOWER

Date: Mon, 21 Dec 1998 17:06:07 -0500

From: "Mark Grady" <mgrady@bnin.net>

Subject: GMC: High speed blower relay, (was Working on "bugs")

Neely -

No, but most likely your high speed blower relay is shot, or the wire that is the power feed to it has corrosion on the push on terminal.

The high speed blower relay kinda' looks like a horn relay. On my '77, it is on the firewall on the passenger's side.

Mark

 

Date: Mon, 21 Dec 1998 16:12:13 -0600

From: Billy Massey <bmassey@web-access.net>

Subject: Re: GMC: Working on "bugs"

I can't find it but I think I remember someone saying that it ran right off a different source than the other speeds. not sure what that means. Mine wasn't working the other day and I wiggled the connector around on the heater box and it started working again. It's accessible through the drivers side front access panel, near the master cylinder.

Hope this helps

bdub

'76 Palm Beach

In The Heart o Texas

www.web-access.net/~bmassey/

icq # 202333

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Neely --

Should have added this to make it more clear:

> No, but most likely your high speed blower relay is shot, or the wire that is the power feed to it has corrosion on the push on terminal.

With the engine off so you can hear better, turn the key on, move the top heater / AC control lever to any setting but "max", then move the fan speed switch up to high.

You should hear a 'clunk' as the relay energizes. That tells you how big your problem is. If you don't hear the clunk, then the relay coil is open or the ground to the relay is no good. You can test for voltage on the coil of the relay with a 12 volt test light.

If you hear the clunk, it could still be the relay, but most likely it is the voltage source to the relay. That wire (which I think is red) carries enough current that the push on connector can go bad.

An easy check is to turn the fan on high (and it won't even be running) then go out front and wiggle the whole plug assembly on the high speed blower relay.

You can also check it with a 12 volt test light, the kind with an awl like pointed end is the best way to test problems like this.

> The high speed blower relay kinda' looks like a horn relay. On my '77, it is

> on the firewall on the passenger's side.

This is under the little access door at the passenger's front of the coach, not inside.

Just re-read the assumptions message and realized I could have done a better job of explaining what I meant.

_______________________________________

 

Date: Mon, 21 Dec 1998 18:17:34 -0700

From: dlowry@silcom.com (Dave Lowry)

Subject: GMC: Working on "bugs"

Neely:

Two possible reasons for no high speed fan: 1) contacts dirty in switch (you'll need to wiggle and push etc.), or 2) you're testing without the engine running (must be to get high speed).

BTDT, HTH

Dave Lowry, '76 Royale, Santa Barbara

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Date: Mon, 21 Dec 1998 18:28:10 PST

From: "Frank Folkmann" <fmfolkmann@hotmail.com>

Subject: Re: GMC: Working on

Had the same problem. Changed the relay. Still no high. The problem with mine was in dash switch. Had to back it of high position just a bit. It still works by doing this. Probably my switch is not indexing correctly.

Frank SW Indiana

 

Date: Mon, 21 Dec 1998 21:35:13 -0500

From: Ritch Hwang <rhwang@concentric.net>

Subject: GMC: High speed blower relay, (was Working on "bugs")

In addition to checking relays, etc, re inoperative blower high speed, here's what I have from the notes taken at a Q & A session w/Duane Simmons, et al, at Marion:

"At the high speed setting, the blower runs direct from the alternator. If you suddenly can't switch to high speed with the engine running while on the road, odds are your alternator has died or you have thrown an alternator belt." Also recommended using a 10 ga ground wire for the blower.

Hope this is helpful....

As always, best regards.

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Date: Tue, 22 Dec 1998 10:11:44, -0500

From: JDDP32B@prodigy.com (MR EUGENE R FISHER)

Subject: GMC: Blower relay

the NAPA number is

AR126

for the blower high speed relay

gene

- --

Gene 76Palm Beach /Or/CA

GMC Technical Information

http://www.california.com/~eagle/

 

Date: Thu, 07 Jan 1999 14:42:45 -0500

From: Thom Hole <THHOLE@cisco.com>

Subject: GMC: GMC Dash Heater Problems

Well, today's challenge is a new one for me. I've got a small amount of what appears to be steam coming out of the dash vents. It doesn't smell like anti-freeze, in fact it doesn't have any smell at all.

I changed the heater A/C controls and that had no effect. It goes away when accelerating and is the heaviest when coasting.

Any thoughts or experience out there??

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Date: Thu, 07 Jan 1999 14:07:54 -0800

From: LARRY DTIMOTHY <ltim@bellsouth.net>

Subject: Re: GMC: GMC Dash Heater Problems

Of course first thought is to look toward Vacuum related parts.

Timothy

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Date: Thu, 7 Jan 1999 15:19:06 EST

From: Gcbr@aol.com

Subject: Re: GMC: GMC Dash Heater Problems

Where are you? Is it cold where you are? Is it hot. Are you trying to use the heater or AC?

Take Care

Arch 76 GB IL

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Date: Thu, 07 Jan 1999 15:29:15 -0500

From: Thom Hole <THHOLE@cisco.com>

Subject: Re: GMC: GMC Dash Heater Problems

North Carolina!! Air temp 45 degrees, sunshine!! Started with heater, but when I saw the 'Steam' I changed the dash controls to other positions to see if it would stop, which it didn't. Driving at 50 mph, it's about the amount that would come off of a freshly poured cup of McDonalds coffee.

Gets worse on coasting from 50 mph with foot off accelerator.

Beyond that, there isn't much that can produce steam. A hole in your radiator could also be producing engine compartment moisture or steam that gets picked up by the heating system fan. You should be able to find that pretty easily with a visual inspection.

Keep in mind that if you're using the new environmentally friendly anti-freeze solutions, they don't have as much stink as the older formulations.

On a remote chance, it could be the windings in your A/C fan burning out, but you'd have the enticing aroma of burning electrical wiring along with the smoke. Let us know what you find, this is an unusual problem!

Mark

 

Date: Thu, 7 Jan 1999 15:56:50 EST

From: Gcbr@aol.com

Subject: Re: GMC: GMC Dash Heater Problems

Thom

First make sure the AC is really off. If the humidity is high and the ac is on it can make condensate that looks like steam.

Take Care

Arch

 

Date: Thu, 7 Jan 1999 22:51:57 EST

From: DEvans753@aol.com

Subject: Re: GMC: GMC Dash Heater Problems

I had a very similar experience, even slight condensation on the inside glass

surfaces. Mine was a very slight weepage of coolant from the heater core --

never leaked or wetted the outside of the heater box under the hood. It was

fairly simple to replace by removing the front cover of the heater box that

straddles the two hood hatches.

Dave Evans

'73 Canyon Lands

Rochester, Michigan

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Date: Thu, 7 Jan 1999 15:40:09 -0500

From: "Mark Grady" <mgrady@bnin.net>

Subject: GMC: GMC Dash Heater Problems (reply)

Thom --

Don't know what the weather's like where you're at, but... I'm surprised that you don't have the sickly sweet smell of anti-freeze. You can look under the heater box by opening the front hood and see if any green ooze is coming out. You might also try to capture some of the 'steam' in a white

facial tissue for color analysis.

If not, and you're where it's humid -- and you have your A/C on -- then you could have a low refrigerant charge. A low charge will cause 'frosting' of the evaporator core and a cold steam like mist to be discharged from the dash vents. Check your refrigerant charge by looking at the

receiver/dehydrator to see if the sight glass is full.

Usually, the thermal limiter fuse on the A/C compressor will blow next, or the low pressure switch will prevent the compressor from engaging. That depends on your coach year. Try putting the top lever in the vent position, which turns off the A/C compressor. See if that stops your steam.

Not as likely, but a hole in your A/C evaporator will also cause refrigerant oil to be forced out. It can look like steam too and not have an odor but feel oily. Again, this problem wouldn't last more than a few minutes before the A/C system lost its charge.

Beyond that, there isn't much that can produce steam. A hole in your radiator could also be producing engine compartment moisture or steam that gets picked up by the heating system fan. You should be able to find that pretty easily with a visual inspection.

Keep in mind that if you're using the new environmentally friendly anti-freeze solutions, they don't have as much stink as the older formulations.

On a remote chance, it could be the windings in your A/C fan burning out, but you'd have the enticing aroma of burning electrical wiring along with the smoke. Let us know what you find, this is an unusual problem!

Mark

 

Hi Thom!

I read all the other 2 cents worth, they might have located your problem. I'd like to give you my experience with a problem similar to yours, however not in a GMC. This car came in to have some work to be done because everytime they turned the heater on the whole inside of the car would steam up because the water vapor was condensing on the colder glass. Our first thought was the heater core or hoses, that stuff was OK. There was no distinct smell like antifreeze in the car. So we removed the whole dash out of the car so we could see the heating ductwork. Needless to say we found a puddle of water that had accumulated in the ductwork. The way the car was built and located, we decided to spray water on the outside of the windshield. The next thing we saw was a trickle of water making its way into this little puddle in the ductwork. Voila-- we resealed the windshield on the outside and they have not had that problem since. (4 yrs ago)

Just some other thoughts!

Scott Adohen@aol.com

 

Date: Sat, 9 Jan 1999 15:44:37 -0700

From: "Richard Guthart" <rguthart@frii.com>

Subject: GMC: A/C & heater blower switch

I frequently have to wiggle the switch on the dash to get my heater/air cond. fan to change speed. Usually it just wants to stay in low regardless of position. This is particularly true of the max position. It will go into max but only after wiggling the switch lever.

I think other owners have noted the same problem (incl. you, Arch?) and I am

wondering if anyone has been able to solve the problem with tuner cleaner (dirty contacts) or have you found that the switch contacts are simply worn out. If so, anybody know of a part number for a replacement switch; just the switch, not the entire heater/air cond control assembly?

It would be nice to know what to expect before I pull the instrument panel bezel.

Thanks,

Richard Guthart

 

Date: Sat, 9 Jan 1999 17:53:39 EST

From: Gcbr@aol.com

Subject: Re: GMC: A/C & heater blower switch

Richard

Yes, I do have the problem. No, I have not got there. Don't forget it will not run in the high position unless the engine is running. I took back one high speed relay because of that. Not to mention a lot of &%#@#$% . Yes, the old one was bad.

Take Care

Arch 76 GB IL down to 14 so still iced in.