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Oct 1, 2010 | 10:12 AM

#31

dchamberlain

Lead Driver

Joined: Sep 2007

Posts: 8,180

Likes: 669

From: Scio, OR

I believe somewhere back in this thread I suggested that the OP get his alternator tested. I still think this is a good idea. If he was having starting problems as he said, then he very likely had an alternator problem. If changing the batteries still results in a starting problem at some point, the alternator remains the only reasonable problem.

But, before replacing anything I believe you should test it.

That being said, if you've concluded that you need an alternator, ignore the hissy fit of the guy who's pissed off because no one is listening to his crap and get the best alternator that you can for the money. I personally would get an OEM one. They're not any more expensive than the others and it's lasted since '05 on your truck so far.

It's true that continual high heat is hard on batteries. But there is no reasonable reason to believe that high heat causes alternators not to output as much, nor will make them fail any quicker. Think about their normal operating environment. It gets pretty damned hot under that hood anyway.

Oct 1, 2010 | 10:23 AM

#32

gearloose1

Post Fiend

Joined: Jul 2005

Posts: 6,127

Likes: 6

dchamberlain false information

Quote:

Originally Posted by dchamberlain

But there is no reasonable reason to believe that high heat causes alternators not to output as much, nor will make them fail any quicker.

The facts are as follows:

Quote:

Excessive heat. An alternator can become damaged if it operates too long at excessive temperatures. Damaging heat levels are generated in two ways: when the alternator becomes dirty either externally or internally restricting its ability to dissipate heat from its external surface or not allowing air to pass through the unit, and when air ducts and heat shields are not replaced after the alternator has been serviced.

Training Manual

Quote:

Output vs Temperature:
Operating temperature also affects output - higher temperatures resulting in lower outputs. Heat reduces output, and shortens alternator life.
“Cold” Amps rating is for an ambient air temperature of 77 degrees Fahrenheit (25 C), such as when an engine is first started, and will often be 10 - 25% higher than the hot rating.
“Hot” Amps rating is for an ambient air temperature of 200 deg. Fahrenheit (93 C), such as when an engine has been operating for some time.
[see chart below]

An Alternator Specification should describe the Output (Amps) at specific Rotor Speeds, and Temperatures. This is usually presented on a curve, but here’s an example of 2 Alternators in chart form:

Alternator RPM = Alt. “A” Cold* / Hot* ~~ Alt. “B” Cold / Hot

2000 RPM = (A)51A Cold / 41A Hot ~~ (B) 42A Cold / 31A Hot

2500 = 78/63 ~~ 73/58
3000 = 92/76 ~~ 93/76
3500 = 102/85 ~~ 107/87
4000 = 108/92 ~~ 117/96
4500 = 114/96 ~~ 123/102
5000 = 118/99 ~~ 127/107
5500 = 121/102 ~~ 131/110
6000 = 123/104 ~~ 134/113

6500 = 124/106 ~~ 136/116

Note:
Alternator “A” might be “rated” at 124 Amps, but will rarely achieve anywhere near that output in actual use. The 124A rating is “cold”, at 6500 rotor RPM (perhaps 3250 Engine RPM). Re-charging at anchor, you might realistically expect something on the order of 63A output (about half it’s rating).

Alternator Specification Basics - Cruisers & Sailing Forums

Quote:

Higher Output at Low RPM
Given below are alternator outputs versus temperature and alternator RPM. Note: All alternators are P-type units except the 32 Volt, #4132 model.

<table border="1" cellpadding="3"> <tbody><tr><td align="LEFT">Alternator</td> <td align="LEFT">#4023</td> <td align="LEFT">#4024</td> </tr> <tr><td align="LEFT">RPM</td> <td align="LEFT">Cold/Hot</td> <td align="LEFT">Cold/Hot</td> </tr> <tr><td align="LEFT">2000</td> <td align="LEFT">51/41</td> <td align="LEFT">42/31</td> </tr> <tr><td align="LEFT">2500</td> <td align="LEFT">78/63</td> <td align="LEFT">73/58</td> </tr> <tr><td align="LEFT">3000</td> <td align="LEFT">92/76</td> <td align="LEFT">93/76</td> </tr> <tr><td align="LEFT">3500</td> <td align="LEFT">102/85</td> <td align="LEFT">107/87</td> </tr> <tr><td align="LEFT">4000</td> <td align="LEFT">108/92</td> <td align="LEFT">117/96</td> </tr> <tr><td align="LEFT">4500</td> <td align="LEFT">114/96</td> <td align="LEFT">123/102</td> </tr> <tr><td align="LEFT">5000</td> <td align="LEFT">118/99</td> <td align="LEFT">127/107</td> </tr> <tr><td align="LEFT">5500</td> <td align="LEFT">121/102</td> <td align="LEFT">131/110</td> </tr> <tr><td align="LEFT">6000</td> <td align="LEFT">123/104</td> <td align="LEFT">134/113</td> </tr> <tr><td align="LEFT">6500</td> <td align="LEFT">124/106</td> <td align="LEFT">136/116</td> </tr> </tbody></table>

12 Volt Alternators ...Small Case

<table border="1" cellpadding="3"> <tbody><tr><td align="LEFT">Alternator</td> <td align="LEFT">#4059</td> <td align="LEFT">#4060</td> <td align="LEFT">#4300</td> </tr> <tr><td align="LEFT">RPM</td> <td align="LEFT">Cold/Hot</td> <td align="LEFT">Cold/Hot</td> <td align="LEFT">Cold/Hot</td> </tr> <tr><td align="LEFT">2000</td> <td align="LEFT">98/87</td> <td align="LEFT">65/60</td> <td align="LEFT">20/13</td> </tr> <tr><td align="LEFT">2500</td> <td align="LEFT">122/110</td> <td align="LEFT">114/105</td> <td align="LEFT">75/66</td> </tr> <tr><td align="LEFT">3000</td> <td align="LEFT">134/124</td> <td align="LEFT">146/133</td> <td align="LEFT">160/130</td> </tr> <tr><td align="LEFT">3500</td> <td align="LEFT">144/131</td> <td align="LEFT">165/150</td> <td align="LEFT">210/175</td> </tr> <tr><td align="LEFT">4000</td> <td align="LEFT">150/134</td> <td align="LEFT">175/162</td> <td align="LEFT">240/205</td> </tr> <tr><td align="LEFT">4500</td> <td align="LEFT">154/138</td> <td align="LEFT">184/169</td> <td align="LEFT">260/225</td> </tr> <tr><td align="LEFT">5000</td> <td align="LEFT">156/141</td> <td align="LEFT">189/174</td> <td align="LEFT">275/243</td> </tr> <tr><td align="LEFT">5500</td> <td align="LEFT">158/142</td> <td align="LEFT">194/175</td> <td align="LEFT">285/252</td> </tr> <tr><td align="LEFT">6000</td> <td align="LEFT">159/144</td> <td align="LEFT">197/179</td> <td align="LEFT">294/267</td> </tr> <tr><td align="LEFT">6500</td> <td align="LEFT">160/147</td> <td align="LEFT">199/181</td> <td align="LEFT">310/275</td> </tr> </tbody></table>

12 Volt Alternators ...Large Case

<table border="1" cellpadding="3"> <tbody><tr><td align="LEFT">Alternator</td> <td align="LEFT">#4109</td> <td align="LEFT">#4110</td> <td align="LEFT">#4132</td> </tr> <tr><td align="LEFT">RPM</td> <td align="LEFT">Cold/Hot</td> <td align="LEFT">Cold/Hot</td> <td align="LEFT">Cold/Hot</td> </tr> <tr><td align="LEFT">2000</td> <td align="LEFT">35/33</td> <td align="LEFT">40/36</td> <td align="LEFT">30/27</td> </tr> <tr><td align="LEFT">2500</td> <td align="LEFT">80/67</td> <td align="LEFT">100/90</td> <td align="LEFT">75/67</td> </tr> <tr><td align="LEFT">3000</td> <td align="LEFT">100/76</td> <td align="LEFT">125/112</td> <td align="LEFT">94/84</td> </tr> <tr><td align="LEFT">3500</td> <td align="LEFT">113/99</td> <td align="LEFT">145/130</td> <td align="LEFT">109/98</td> </tr> <tr><td align="LEFT">4000</td> <td align="LEFT">119/107</td> <td align="LEFT">158/142</td> <td align="LEFT">118/106</td> </tr> <tr><td align="LEFT">4500</td> <td align="LEFT">123/111</td> <td align="LEFT">170/153</td> <td align="LEFT">127/115</td> </tr> <tr><td align="LEFT">5000</td> <td align="LEFT">126/114</td> <td align="LEFT">175/157</td> <td align="LEFT">131/118</td> </tr> <tr><td align="LEFT">5500</td> <td align="LEFT">128/117</td> <td align="LEFT">178/160</td> <td align="LEFT">133/120</td> </tr> <tr><td align="LEFT">6000</td> <td align="LEFT">130/119</td> <td align="LEFT">180/162</td> <td align="LEFT">135/121</td> </tr> <tr><td align="LEFT">6500</td> <td align="LEFT">135/120</td> <td align="LEFT">181/163</td> <td align="LEFT">136/122</td> </tr> </tbody></table>

24 and 32 Volt Alternators ...Large Case

How good are Ample Alternators? Compare the output current given above to the outputs of other brands at the same alternator RPM and at the same temperature. You'll discover that Ample Alternators put out more Amps at every point! Alternator RPM is given, not engine RPM. Engine RPM is always less ... it depends on the pulley ratios. A Yanmar engine with a 5.4 inch, (132 mm), pulley running at 1200 RPM will spin an alternator with a 2.6 inch, (66 mm), pulley at 2500 RPM. In the rating charts the cold Amps rating is for an ambient air temperature of

Fahrenheit, (

C). The hot Amps rating is for an ambient air temperature of

Fahrenheit, (

C). Typical operating temperatures are much less ...expect more than the hot ratin

Ample Power Alternators

Every automotive grade / mass market alternator manufacturer acknowledge that higher temperatures will result in lower output.

Tell me where you get your alternators and where you find the science and facts to back up your statements.

dchamberline:

You were caught posting false information with respect to the voltage test, misleading the OP into believing there is a problem with the voltage when in fact, it test within spec.

Now you claim that " no reasonable reason to believe that high heat causes alternators not to output as much".

The information is factually false.

Stop posting false information on this forum.

Oct 1, 2010 | 10:26 AM

#33

glruff

FTE Leadership Emeritus

Joined: Aug 2006

Posts: 47,280

Likes: 172

From: DELAWARE, The First State

Ok enough bashing, snide remarks, this thread is closed until forum mod has a chance to look at the tone of the posts being made and the attacks on each other.

Oct 1, 2010 | 12:19 PM

#34

Maxium4x4

Super Moderator

Joined: Jul 2004

Posts: 21,113

Likes: 3,939

From: Ohio

Such a nice day outside.....

I agree with George, the thread will stay closed. In the future, think about what you post.

To the original poster 13.8-14.2 is ideal from the alternator.