| High Blower Relay [message #206828] |
Sat, 04 May 2013 16:59  |
Wayne
Messages: 106
Registered: August 2004
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Hi everyone,
My high blower is inoperative under all settings and conditions. Every thing else is fine. There was high resistance at the plug but now it is fixed. There is a feed wire, 14 red w double white stripes , at the high blower relay. That red wire ties in to a 18g fusible link.
I believe the fusible link is blown because I can't get power out of it under any conditions. If I bypass it with a wire direct to the batt everything works.
Does anyone know the easiest way to get to the fusible link. I have no problem making a new fusible link but is it supposed to tie in to the 12 batt or 12 ign?
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: High Blower Relay [message #206850 is a reply to message #206828] |
Sun, 05 May 2013 08:26  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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A Ken Henderson large wiring diagram for a 76 chassis would give the real answer. The fusible link material should be availabe at a real auto parts store. I spray all the connectors with Caig D5 yearly. All GMs of the era would melt the connectors when resistance built from oxidation.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: High Blower Relay [message #206851 is a reply to message #206828] |
Sun, 05 May 2013 08:35 |
skip2
Messages: 544
Registered: September 2011
Location: Winter Haven,FL (center o...
Karma: 3
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Is the 455 running? if I remember correctly high speed is powered directly off of the alternator output that is what the relay directs to the blower.
Skip hartline
74 Canyon Lands, FiTech,
3.7 FD LSD, Manny Tranny,
Springfield Distributor,
2001 Chevy Tracker Ragtop Towd
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| Re: [GMCnet] High Blower Relay [message #206857 is a reply to message #206850] |
Sun, 05 May 2013 09:18 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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John uses the following D5:
http://store.caig.com
A little expensive but work very well.
JR Wright
78 Buskirk Stretch
Michigan
On May 5, 2013, at 9:26 AM, John R. Lebetski <gransport@aol.com> wrote:
>
>
> A Ken Henderson large wiring diagram for a 76 chassis would give the real answer. The fusible link material should be available at a real auto parts store. I spray all the connectors with Caig D5 yearly. All GMs of the era would melt the connectors when resistance built from oxidation.
> --
> John Lebetski
> Chicago, IL
> 77 Eleganza II
> Source America First
> _______________________________________________
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: High Blower Relay [message #206926 is a reply to message #206828] |
Sun, 05 May 2013 23:00 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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First. There is only power on the high speed lead of the blower relay when the alternator is running.
Second, you can get replacement fusible link wire at Auto Zone and most other auto parts stores hanging on a bubble pack card in the electrical section.
Make sure the engine (and alternator) are running when testing the high speed blower circuit.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: High Blower Relay [message #206970 is a reply to message #206926] |
Mon, 06 May 2013 11:35 |
Wayne
Messages: 106
Registered: August 2004
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Hi Blower has now turned into alt not charging.
Can't (don't want to) make tests now as it is raining.
Thanks for the help so far.
I will report back after testing.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: High Blower Relay [message #207270 is a reply to message #206828] |
Thu, 09 May 2013 17:32 |
Wayne
Messages: 106
Registered: August 2004
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Well, it turns out that ever thing that can go wrong will go wrong if you keep it long enough.
I checked the wires as per the shop manual and all were ok. I removed alt and took to local Autozone for checking. It passed all the tests. On my way back to the car I had the alt in my hand , by my ear, and heard a rattle. I have never heard any rattle in an alt before so I decided to take it apart before reinstalling it. Its a good thing I did. The brushes were worn so bad that a little piece broke off.
I replaced the brushes and both bearings. Now works too good.
With everything off batt voltage 12.60. Idling batt volts 14.06. The isolator center lug is 15.40. Is this too high?
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: High Blower Relay [message #207272 is a reply to message #207270] |
Thu, 09 May 2013 18:11 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Wayne wrote on Thu, 09 May 2013 17:32 |
Well, it turns out that ever thing that can go wrong will go wrong if you keep it long enough.
I checked the wires as per the shop manual and all were ok. I removed alt and took to local Autozone for checking. It passed all the tests. On my way back to the car I had the alt in my hand , by my ear, and heard a rattle. I have never heard any rattle in an alt before so I decided to take it apart before reinstalling it. Its a good thing I did. The brushes were worn so bad that a little piece broke off.
I replaced the brushes and both bearings. Now works too good.
With everything off batt voltage 12.60. Idling batt volts 14.06. The isolator center lug is 15.40. Is this too high?
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The readings are a little strange. I am suspecting a voltage drop between the isolator and the battery. Probably at the fusible link. With the engine running, read the center terminal of the isolator and then immediately read the top and bottom terminals of the isolator. After that read the voltage at each battery. Please post the numbers.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: High Blower Relay [message #207279 is a reply to message #206828] |
Thu, 09 May 2013 19:11 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Hi Ken,
The center post engine running @ idle 15.65
The top post "" "" "" 14.40
The bottom post "" "" "" 14.60
house batt "" "" "" 13.85
car batt "" "" "" 14.29
Both batt NOT running 12.52
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: High Blower Relay [message #207280 is a reply to message #206828] |
Thu, 09 May 2013 19:20 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Those readings look great to me. As it gets hotter out you should drop a couple tenths. Never trusted the auto parts bench test myself.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] High Blower Relay [message #207281 is a reply to message #207279] |
Thu, 09 May 2013 19:21 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Wayne, another dynamic test you can do is to turn on the headlamps, blower
on high speed, A/C on max. Then recheck the center post on the isolator at
1500 rpm or so. Values should be nearly the same or slightly lower. The
upper and lower posts on the isolator sound about right to me for a system
with batteries that need some charging. Under lab conditions, a lead acid
battery in an "ideal" state of charge can have 2.2 volts per cell, or 13.2
volts total. Charging voltage from the alternator needs to be a volt higher
than that to effectively charge the batteries. 14.2 to 14.5 sounds about
right depending on the accuracy of the meter used to measure the voltage.
Don't want it much higher than that though.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Thu, May 9, 2013 at 5:11 PM, Wayne Lawrence <wayne4@ca.rr.com> wrote:
>
>
> Hi Ken,
>
> The center post engine running @ idle 15.65
> The top post "" "" "" 14.40
> The bottom post "" "" "" 14.60
>
> house batt "" "" "" 13.85
>
> car batt "" "" "" 14.29
>
> Both batt NOT running 12.52
> --
> Wayne Lawrence
> 76 Birchaven
> Bellflower CA
> wayne4@ca.rr.com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: High Blower Relay [message #207286 is a reply to message #207279] |
Thu, 09 May 2013 20:36 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Wayne wrote on Thu, 09 May 2013 19:11 |
Hi Ken,
The center post engine running @ idle 15.65
The top post "" "" "" 14.40
The bottom post "" "" "" 14.60
house batt "" "" "" 13.85
car batt "" "" "" 14.29
Both batt NOT running 12.52
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OK here is what bothers me.
1. There should be about .7 volt drop going through the isolator. In yours there is a 1.25 volt drop on the house side and 1.05 volt drop on the engine side. (I may have these reversed. I always have to look at the wires to be sure.) either way the drop is out of specs.
2. After the isolator there is an additional drop of .3 volt on the engine side. I can understand this because it goes through some additional wiring to get to the battery. The biggest drop is probably through the fusible link.
3. On the house side the additional drop is even higher at .6 volts. This route to the house battery does not contain a fusible link and I would expect that drop to be even less than the engine side. Charging the house batteries at 13.8 volts will take a longer time to come up to full charge.
4. Battery at rest voltages of 12.52 are a little low indicating that they are not fully charged or are are old and weak.
Conclusions:
I believe you have an isolator going bad. You might want to replace it with a new one or a combiner. These could be bad connections at the isolator. You might want to clean (polish) them up and replace the nuts with stainless one first.
I believe you have some other marginal connections, especially on the house side. I would be looking for those.
Keep in mind that the battery charging ground path between the alternator and the house batteries goes through the ground jumpers located on the back of the transmission and the second one between the body and the frame. That second one is located in right front in front of the front wheel. Rather than go physically looking at these you can test them first with a voltmeter to see if they are your problem. Hook a voltmeter between any body ground and the engine. Then read the drop with the engine running.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: High Blower Relay [message #207290 is a reply to message #206828] |
Thu, 09 May 2013 22:34 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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On the house side the grd is down at the corner of the batt box. A perfect spot for road splash and acid leach and bimetalic reaction.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] High Blower Relay [message #207351 is a reply to message #207310] |
Fri, 10 May 2013 19:54 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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Hi Ken,
The center post engine running @ idle 15.65
The top post "" "" "" 14.40
The bottom post "" "" "" 14.60
house batt "" "" "" 13.85
car batt "" "" "" 14.29
Both batt NOT running 12.52
After charging both batteries and cleaning all connections on the sol and isolator. The voltage drop on the neg side of charging sys is less then .1 volt (.09)
NEW NUMBERS
The center post engine running @ idle 15.63
The top post "" "" "" 14.60
The bottom post "" "" "" 14.58
house batt "" "" "" 13.78
car batt "" "" "" 14.56
Both batt NOT running 12.80
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: [GMCnet] High Blower Relay [message #207359 is a reply to message #207351] |
Fri, 10 May 2013 22:46 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Wayne wrote on Fri, 10 May 2013 19:54 |
Hi Ken,
After charging both batteries and cleaning all connections on the sol and isolator. The voltage drop on the neg side of charging sys is less then .1 volt (.09)
NEW NUMBERS
The center post engine running @ idle 15.63
The top post "" "" "" 14.60
The bottom post "" "" "" 14.58
house batt "" "" "" 13.78
car batt "" "" "" 14.56
Both batt NOT running 12.80
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Well, It will run that way. I believe you are saying that both batteries are now reading 12.8 after charging. If so then the batteries are OK.
1. I'm still a little confused /concerned by the 1 volt drop through the isolator to both the house and engine terminals.
2. You should be able to find the .7 drop on the house side between the isolator and the battery. You stated that the ground side drop is only .1 so that eliminates any bad connections on the negative side. On the positive side I would connect one lead of the voltmeter to the house side terminal of the isolator. With the other lead start probing the connections in the path to the house battery (solenoid, etc.) looking for that .7 volts drop. The engine must be running during this test.
3. The final item that concerns me is the high charging voltage on the engine side. 14.6 is a bit much at the battery. It is almost like the alternator remote sense line is hooked to the house side rather than the engine side. It would be interesting, but difficult to to probe the sense line voltage at the alternator with the engine running. That alternator is running a little too high but we do not at this point know if it is running high because of an alternator-regulator problem or if it is because the remote sense line is reading low.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: High Blower Relay [message #207402 is a reply to message #206828] |
Sat, 11 May 2013 15:54 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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Hi Ken,
After charging both batteries and cleaning all connections on the sol and isolator. The voltage drop on the neg side of charging sys is less then .1 volt (.09)
NEW NUMBERS
The center post engine running @ idle 15.63
The top post "" "" "" 14.60
The bottom post "" "" "" 14.58
house batt "" "" "" 13.78
car batt "" "" "" 14.56
Both batt NOT running 12.80
MORE NEW NUMBERS 5/11/2013
Cleaned batt cables, wires at stud on horn relay, and connection terminal for sense wire at alt.
I did probe the sense wire and it is the same as the car batt running voltage.
The center post engine running @ idle 15.45
The top post car engine running 14.45
The bottom post house engine running 14.46
house batt engine running 13.69
car batt engine running 14.41
Car batt not running 12.72
House batt not running 12.63
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: High Blower Relay [message #207421 is a reply to message #206828] |
Sat, 11 May 2013 20:17 |
Wayne
Messages: 106
Registered: August 2004
Karma: 0
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Senior Member |
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The house batt is beside the car batt. not in the back. I though maybe slight difference in batt state of charge or house is deep cycle and car is basic car batt. I checked from pos post on house batt to house post on isolator no voltage drop. I am thinking of switching cables as I think they are long enough.
Wayne Lawrence
76 Birchaven
Bellflower CA
w.lawrence@verizon.net
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| Re: High Blower Relay [message #207434 is a reply to message #207421] |
Sun, 12 May 2013 01:04 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Wayne wrote on Sat, 11 May 2013 20:17 |
The house batt is beside the car batt. not in the back. I though maybe slight difference in batt state of charge or house is deep cycle and car is basic car batt. I checked from pos post on house batt to house post on isolator no voltage drop. I am thinking of switching cables as I think they are long enough.
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Where are we loosing the .7 or .8 volts on the house battery?
If I understand correctly you have no voltage drop on the positive side of the house battery to the isolator. You also have only a .1 volt drop between the negative side of the house battery and the engine block which is the master ground for the engine charging system and the alternator. Something does not make sense here.
If you read 14.6 or 14.7 at the sense line on the alternator, then the alternator regulator should be reducing the output voltage until it sees around 14.0 on the sense line. There are some regulators that are temperature sensitive and charge at a higher voltage when they are cold. I do not know if they ever made one for the GMC alternator. I am not an expert on those alternators.
It might be interesting to run the coach for a while down the road and read the outputs of the isolator to both the house and engine batteries again. Maybe we are chasing an insignificant phantom that goes away when the engine is hot.
While both of the readings at the two batteries are sightly above and below spec respectively, the coach will still run OK. Just keep an eye on the electrolyte (water) level on the engine battery to make sure you do not boil it dry.
I'm still stumped as to where the .8 volt drop is occurring on the house side and why we are dropping 1+ volt through the isolator to both house and engine outputs. I am suspicious of the isolator but not enough to tell you to replace it unless you have a free one around to try. I hate throwing parts at something that may not really be broken.
Do you have one of gene's APCs installed on your alternator? I'm wondering if it possibly could have a bad crimp connection on the sense line. Also could you possible have a marginal connection where the alternator cable (sense line) plugs into the alternator. I really guessing now.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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